Porting FreeRTOS to RISC-V, Based on the Vectored-Interrupt Mode.

 

※ The source code is here, the Vector_Mode_Implementation tag.

※ This porting is based on the RISC-V user mode, identical to the WCH's version, if you are interested in the machine mode porting, please refer to my next post.

     FreeRTOS and RISC-V are becoming more and more popular, for both of them are license-free and generic, thus they are gradually turning into the Industry mainstream. Especially in the ASIC(application-specific integrated circuit) purposes, a simple CPU core with a lightweight operation system to manage the special purpose hardware resources, this couple is an ideal solution.

     However, for a beginner, proting FreeRTOS is a dos of hardwork, it is inevitable  to involve with assembly, and read the data-sheet to know the instruction-level mechanism. This post try to relief this pain,  shows how to port FreeRTOS to RISV-C.

   Here I use the chip WCH CH32V307, whose offical github has provided a FreeRTOS porting. This post will begin from scratch, to demonstrate how to complete the porting as the offical work.

That porting is based on vectored-interrupt. which feature is not supported with every RISC-V chip. 

The offical porting is based on vectored-Interrupt mode. but this feature is not supported with every RISC-V chip. Thus, in the next post, I will show how to use the other mode, direct-interrupt, to bring the FreeRTOS workable.

  零. Download and Prepare the folders. 

    Download FreeRTOS, the version I use is FreeRTOS 202112.00. Prepare a folder, named as ch32v307_FreeRTOS, which structure is as below : 

  ch32v307_FreeRTOS

├─Core
├─Debug
├─FreeRTOS
│  └─Source
│      ├─include
│      └─portable
│          ├─Common
│          ├─GCC
│          │  └─RISC-V
│          │      └─chip_specific_extensions
│          │          └─RV32I_PFIC_no_extensions
│          └─MemMang
├─Ld
├─Peripheral
│  ├─inc
│  └─src
├─Startup
└─User

     Where FreeRTOS is from the zip ball FreeRTOS zip ball subdir, FreeRTOS (FreeRTOSv202112.00\FreeRTOS), the others folders contained in the ball should be deleted. RV32I_PFIC_no_extensions does not contain in the zip ball, you should create it.

    Startup folder are from CH32V307 offical github FreeRTOS folder .

    The folders, Core, Debug, Ld and Peripheral, are from WCH CH32V307 offical github SRC folder. The User folder contain, could be from any example's User folder. (I use EXTI). 

一. Create a MounRiver project. 

Set a MounRiver project for FreeRTOS. The project file should be placed at ch32v307_FreeRTOS folder. 

Select the chip as the figure :

Add the include paths :

Assembly : 

   /${ProjName}/Startup

   /${ProjName}/FreeRTOS/Source/portable/GCC/RISC-V/chip_specific_extensions/RV32I_PFIC_no_extensions

GNU C :

   /${ProjName}/Core

   /${ProjName}/Peripheral/inc

   /${ProjName}/Debug

   /${ProjName}/User

   /${ProjName}/FreeRTOS/Source/include

   /${ProjName}/FreeRTOS/Source/portable/GCC/RISC-V

And set SVD path for debugging the peripherals :

Exclude the files : 

FreeRTOS\Source\portable\Common\mpu_wrappers.c

FreeRTOS\Source\portable\MemMang\heap_1.c

FreeRTOS\Source\portable\MemMang\heap_2.c

FreeRTOS\Source\portable\MemMang\heap_3.c

FreeRTOS\Source\portable\MemMang\heap_5.c

二. Add and modify the linker script and startup assembly.

   In file Ld/Link.ld, about line 180, change the code as:

:
	PROVIDE( end = . );

    .stack ORIGIN(RAM) + LENGTH(RAM) - __stack_size :
    {
        PROVIDE( _heap_end = . );    
        . = ALIGN(4);
        PROVIDE(_susrstack = . );
        . = . + __stack_size;
        PROVIDE( _eusrstack = .);
        /*add the line*/
        __freertos_irq_stack_top = .;
    } >RAM 

}

This variable is necessary for the file FreeRTOS\Source\portable\GCC\RISC-V\port.c

(Maybe not necessary)For file Startup/startup_ch32v30x_D8C.S , correct the letter case, about line 45 :

:
    .word   0
    .word   SysTick_Handler            /* SysTick */
    .word   0
    .word   SW_Handler                 /* SW */
    .word   0
    /* External Interrupts */
    .word   WWDG_IRQHandler            /* Window Watchdog */
:

(Change  SW_hander to SW_Hander, to make the interrupt callback funtion names are consisted)

三. Add and modify the FreeRTOS code.

Add FreeRTOSConfig.h under the User folder :

/*
 * FreeRTOS V202112.00
 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

#ifndef FREERTOS_CONFIG_H
#define FREERTOS_CONFIG_H

#include "debug.h"

/*-----------------------------------------------------------
 * Application specific definitions.
 *
 * These definitions should be adjusted for your particular hardware and
 * application requirements.
 *
 * THESE PARAMETERS ARE DESCRIBED WITHIN THE 'CONFIGURATION' SECTION OF THE
 * FreeRTOS API DOCUMENTATION AVAILABLE ON THE FreeRTOS.org WEB SITE.
 *
 * See http://www.freertos.org/a00110.html.
 *----------------------------------------------------------*/

/* See https://www.freertos.org/Using-FreeRTOS-on-RISC-V.html */

/* don't have MTIME */
#define configMTIME_BASE_ADDRESS     ( 0 )
#define configMTIMECMP_BASE_ADDRESS  ( 0 )

#define configUSE_PREEMPTION            1
#define configUSE_IDLE_HOOK             0
#define configUSE_TICK_HOOK             0
#define configCPU_CLOCK_HZ              SystemCoreClock
#define configSYSTICK_CLOCK_HZ          HSE_VALUE
#define configTICK_RATE_HZ              ( ( TickType_t ) 500 )
#define configMAX_PRIORITIES            ( 15 )
#define configMINIMAL_STACK_SIZE        ( ( unsigned short ) 256 ) /* Can be as low as 60 but some of the demo tasks that use this constant require it to be higher. */
#define configTOTAL_HEAP_SIZE           ( ( size_t ) ( 12 * 1024 ) )
#define configMAX_TASK_NAME_LEN         ( 16 )
#define configUSE_TRACE_FACILITY        0
#define configUSE_16_BIT_TICKS          0
#define configIDLE_SHOULD_YIELD         0
#define configUSE_MUTEXES               1
#define configQUEUE_REGISTRY_SIZE       8
#define configCHECK_FOR_STACK_OVERFLOW  0
#define configUSE_RECURSIVE_MUTEXES     1
#define configUSE_MALLOC_FAILED_HOOK    0
#define configUSE_APPLICATION_TASK_TAG  0
#define configUSE_COUNTING_SEMAPHORES   1
#define configGENERATE_RUN_TIME_STATS   0
#define configUSE_PORT_OPTIMISED_TASK_SELECTION 0

/* Co-routine definitions. */
#define configUSE_CO_ROUTINES           0
#define configMAX_CO_ROUTINE_PRIORITIES ( 2 )

/* Software timer definitions. */
#define configUSE_TIMERS                1
#define configTIMER_TASK_PRIORITY       ( configMAX_PRIORITIES - 1 )
#define configTIMER_QUEUE_LENGTH        4
#define configTIMER_TASK_STACK_DEPTH    ( configMINIMAL_STACK_SIZE )



/* Set the following definitions to 1 to include the API function, or zero
to exclude the API function. */
#define INCLUDE_vTaskPrioritySet            1
#define INCLUDE_uxTaskPriorityGet           1
#define INCLUDE_vTaskDelete                 1
#define INCLUDE_vTaskCleanUpResources       1
#define INCLUDE_vTaskSuspend                1
#define INCLUDE_vTaskDelayUntil             1
#define INCLUDE_vTaskDelay                  1
#define INCLUDE_eTaskGetState               1
#define INCLUDE_xTimerPendFunctionCall      1
#define INCLUDE_xTaskAbortDelay             1
#define INCLUDE_xTaskGetHandle              1
#define INCLUDE_xSemaphoreGetMutexHolder    1


/* Normal assert() semantics without relying on the provision of an assert.h
header file. */
#define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); printf("err at line %d of file \"%s\". \r\n ",__LINE__,__FILE__); while(1); }

/* Map to the platform printf function. */
#define configPRINT_STRING( pcString )  printf( pcString )


#endif /* FREERTOS_CONFIG_H */

Add the file freertos_risc_v_chip_specific_extensions.h at FreeRTOS\Source\portable\GCC\RISC-V\chip_specific_extensions\RV32I_PFIC_no_extensions :

/*
 * FreeRTOS Kernel V10.4.6
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

/*
 * The FreeRTOS kernel's RISC-V port is split between the the code that is
 * common across all currently supported RISC-V chips (implementations of the
 * RISC-V ISA), and code that tailors the port to a specific RISC-V chip:
 *
 * + FreeRTOS\Source\portable\GCC\RISC-V-RV32\portASM.S contains the code that
 *   is common to all currently supported RISC-V chips.  There is only one
 *   portASM.S file because the same file is built for all RISC-V target chips.
 *
 * + Header files called freertos_risc_v_chip_specific_extensions.h contain the
 *   code that tailors the FreeRTOS kernel's RISC-V port to a specific RISC-V
 *   chip.  There are multiple freertos_risc_v_chip_specific_extensions.h files
 *   as there are multiple RISC-V chip implementations.
 *
 * !!!NOTE!!!
 * TAKE CARE TO INCLUDE THE CORRECT freertos_risc_v_chip_specific_extensions.h
 * HEADER FILE FOR THE CHIP IN USE.  This is done using the assembler's (not the
 * compiler's!) include path.  For example, if the chip in use includes a core
 * local interrupter (CLINT) and does not include any chip specific register
 * extensions then add the path below to the assembler's include path:
 * FreeRTOS\Source\portable\GCC\RISC-V-RV32\chip_specific_extensions\RV32I_CLINT_no_extensions
 *
 */


#ifndef __FREERTOS_RISC_V_EXTENSIONS_H__
#define __FREERTOS_RISC_V_EXTENSIONS_H__

#define portasmHAS_SIFIVE_CLINT 0
#define portasmHAS_MTIME 0
/* if you want to use FPU, please define ARCH_FPU and enable float point and ABI of gcc */
#define ARCH_FPU 0


#if ARCH_FPU
#define portasmADDITIONAL_CONTEXT_SIZE 32 /* Must be even number on 32-bit cores. */
.macro portasmSAVE_ADDITIONAL_REGISTERS
    addi sp, sp, -(portasmADDITIONAL_CONTEXT_SIZE* portWORD_SIZE)
    fsw f0, 1*portWORD_SIZE(sp)
    fsw f1, 2*portWORD_SIZE(sp)
    fsw f2, 3*portWORD_SIZE(sp)
    fsw f3, 4*portWORD_SIZE(sp)
    fsw f4, 5*portWORD_SIZE(sp)
    fsw f5, 6*portWORD_SIZE(sp)
    fsw f6, 7*portWORD_SIZE(sp)
    fsw f7, 8*portWORD_SIZE(sp)
    fsw f8, 9*portWORD_SIZE(sp)
    fsw f9, 10*portWORD_SIZE(sp)
    fsw f10, 11*portWORD_SIZE(sp)
    fsw f11, 12*portWORD_SIZE(sp)
    fsw f12, 13*portWORD_SIZE(sp)
    fsw f13, 14*portWORD_SIZE(sp)
    fsw f14, 15*portWORD_SIZE(sp)
    fsw f15, 16*portWORD_SIZE(sp)
    fsw f16, 17*portWORD_SIZE(sp)
    fsw f17, 18*portWORD_SIZE(sp)
    fsw f18, 19*portWORD_SIZE(sp)
    fsw f19, 20*portWORD_SIZE(sp)
    fsw f20, 21*portWORD_SIZE(sp)
    fsw f21, 22*portWORD_SIZE(sp)
    fsw f22, 23*portWORD_SIZE(sp)
    fsw f23, 24*portWORD_SIZE(sp)
    fsw f24, 25*portWORD_SIZE(sp)
    fsw f25, 26*portWORD_SIZE(sp)
    fsw f26, 27*portWORD_SIZE(sp)
    fsw f27, 28*portWORD_SIZE(sp)
    fsw f28, 29*portWORD_SIZE(sp)
    fsw f29, 30*portWORD_SIZE(sp)
    fsw f30, 31*portWORD_SIZE(sp)
    fsw f31, 32*portWORD_SIZE(sp)
	.endm

.macro portasmRESTORE_ADDITIONAL_REGISTERS
    flw f0, 1*portWORD_SIZE(sp)
    flw f1, 2*portWORD_SIZE(sp)
    flw f2, 3*portWORD_SIZE(sp)
    flw f3, 4*portWORD_SIZE(sp)
    flw f4, 5*portWORD_SIZE(sp)
    flw f5, 5*portWORD_SIZE(sp)
    flw f6, 5*portWORD_SIZE(sp)
    flw f7, 5*portWORD_SIZE(sp)
    flw f8, 5*portWORD_SIZE(sp)
    flw f9, 5*portWORD_SIZE(sp)
    flw f10, 5*portWORD_SIZE(sp)
    flw f11, 5*portWORD_SIZE(sp)
    flw f12, 5*portWORD_SIZE(sp)
    flw f13, 5*portWORD_SIZE(sp)
    flw f14, 5*portWORD_SIZE(sp)
    flw f15, 5*portWORD_SIZE(sp)
    flw f16, 5*portWORD_SIZE(sp)
    flw f17, 5*portWORD_SIZE(sp)
    flw f18, 5*portWORD_SIZE(sp)
    flw f19, 5*portWORD_SIZE(sp)
    flw f20, 5*portWORD_SIZE(sp)
    flw f21, 5*portWORD_SIZE(sp)
    flw f22, 5*portWORD_SIZE(sp)
    flw f23, 5*portWORD_SIZE(sp)
    flw f24, 5*portWORD_SIZE(sp)
    flw f25, 5*portWORD_SIZE(sp)
    flw f26, 5*portWORD_SIZE(sp)
    flw f27, 5*portWORD_SIZE(sp)
    flw f28, 5*portWORD_SIZE(sp)
    flw f29, 5*portWORD_SIZE(sp)
    flw f30, 5*portWORD_SIZE(sp)
    flw f31, 5*portWORD_SIZE(sp)
    addi sp, sp, (portasmADDITIONAL_CONTEXT_SIZE* portWORD_SIZE)
	.endm
#else
#define portasmADDITIONAL_CONTEXT_SIZE 0 /* Must be even number on 32-bit cores. */


.macro portasmSAVE_ADDITIONAL_REGISTERS
    /* No additional registers to save, so this macro does nothing. */
    .endm

.macro portasmRESTORE_ADDITIONAL_REGISTERS
    /* No additional registers to restore, so this macro does nothing. */
    .endm

#endif

#endif /* __FREERTOS_RISC_V_EXTENSIONS_H__ */

Modify FreeRTOS\Source\portable\GCC\RISC-V\port.c as :

/*
 * FreeRTOS Kernel V10.4.6
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the RISC-V RV32 port.
 *----------------------------------------------------------*/

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "portmacro.h"

/* Standard includes. */
#include "string.h"

#ifdef configCLINT_BASE_ADDRESS
	#warning The configCLINT_BASE_ADDRESS constant has been deprecated.  configMTIME_BASE_ADDRESS and configMTIMECMP_BASE_ADDRESS are currently being derived from the (possibly 0) configCLINT_BASE_ADDRESS setting.  Please update to define configMTIME_BASE_ADDRESS and configMTIMECMP_BASE_ADDRESS dirctly in place of configCLINT_BASE_ADDRESS.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

#ifndef configMTIME_BASE_ADDRESS
	#warning configMTIME_BASE_ADDRESS must be defined in FreeRTOSConfig.h.  If the target chip includes a memory-mapped mtime register then set configMTIME_BASE_ADDRESS to the mapped address.  Otherwise set configMTIME_BASE_ADDRESS to 0.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

#ifndef configMTIMECMP_BASE_ADDRESS
	#warning configMTIMECMP_BASE_ADDRESS must be defined in FreeRTOSConfig.h.  If the target chip includes a memory-mapped mtimecmp register then set configMTIMECMP_BASE_ADDRESS to the mapped address.  Otherwise set configMTIMECMP_BASE_ADDRESS to 0.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

/* Let the user override the pre-loading of the initial LR with the address of
prvTaskExitError() in case it messes up unwinding of the stack in the
debugger. */
#ifdef configTASK_RETURN_ADDRESS
	#define portTASK_RETURN_ADDRESS	configTASK_RETURN_ADDRESS
#else
	#define portTASK_RETURN_ADDRESS	prvTaskExitError
#endif

/* The stack used by interrupt service routines.  Set configISR_STACK_SIZE_WORDS
to use a statically allocated array as the interrupt stack.  Alternative leave
configISR_STACK_SIZE_WORDS undefined and update the linker script so that a
linker variable names __freertos_irq_stack_top has the same value as the top
of the stack used by main.  Using the linker script method will repurpose the
stack that was used by main before the scheduler was started for use as the
interrupt stack after the scheduler has started. */
#ifdef configISR_STACK_SIZE_WORDS
	static __attribute__ ((aligned(16))) StackType_t xISRStack[ configISR_STACK_SIZE_WORDS ] = { 0 };
	const StackType_t xISRStackTop = ( StackType_t ) &( xISRStack[ configISR_STACK_SIZE_WORDS & ~portBYTE_ALIGNMENT_MASK ] );

	/* Don't use 0xa5 as the stack fill bytes as that is used by the kernerl for
	the task stacks, and so will legitimately appear in many positions within
	the ISR stack. */
	#define portISR_STACK_FILL_BYTE	0xee
#else
	extern const uint32_t __freertos_irq_stack_top[];
	const StackType_t xISRStackTop = ( StackType_t ) __freertos_irq_stack_top;
#endif

#if(1)//GAIGER
static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
#endif
/*
 * Setup the timer to generate the tick interrupts.  The implementation in this
 * file is weak to allow application writers to change the timer used to
 * generate the tick interrupt.
 */
void vPortSetupTimerInterrupt( void ) __attribute__(( weak ));

/*-----------------------------------------------------------*/

#if( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 ) /*GAIGER*/
/* Used to program the machine timer compare register. */
uint64_t ullNextTime = 0ULL;
const uint64_t *pullNextTime = &ullNextTime;
const size_t uxTimerIncrementsForOneTick = ( size_t ) ( ( configCPU_CLOCK_HZ ) / ( configTICK_RATE_HZ ) ); /* Assumes increment won't go over 32-bits. */
uint32_t const ullMachineTimerCompareRegisterBase = configMTIMECMP_BASE_ADDRESS;
volatile uint64_t * pullMachineTimerCompareRegister = NULL;
#endif

/* Set configCHECK_FOR_STACK_OVERFLOW to 3 to add ISR stack checking to task
stack checking.  A problem in the ISR stack will trigger an assert, not call the
stack overflow hook function (because the stack overflow hook is specific to a
task stack, not the ISR stack). */
#if defined( configISR_STACK_SIZE_WORDS ) && ( configCHECK_FOR_STACK_OVERFLOW > 2 )
	#warning This path not tested, or even compiled yet.

	static const uint8_t ucExpectedStackBytes[] = {
									portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,		\
									portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,		\
									portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,		\
									portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE,		\
									portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE, portISR_STACK_FILL_BYTE };	\

	#define portCHECK_ISR_STACK() configASSERT( ( memcmp( ( void * ) xISRStack, ( void * ) ucExpectedStackBytes, sizeof( ucExpectedStackBytes ) ) == 0 ) )
#else
	/* Define the function away. */
	#define portCHECK_ISR_STACK()
#endif /* configCHECK_FOR_STACK_OVERFLOW > 2 */

/*-----------------------------------------------------------*/

#if( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 )

	void vPortSetupTimerInterrupt( void )
	{
	uint32_t ulCurrentTimeHigh, ulCurrentTimeLow;
	volatile uint32_t * const pulTimeHigh = ( volatile uint32_t * const ) ( ( configMTIME_BASE_ADDRESS ) + 4UL ); /* 8-byte typer so high 32-bit word is 4 bytes up. */
	volatile uint32_t * const pulTimeLow = ( volatile uint32_t * const ) ( configMTIME_BASE_ADDRESS );
	volatile uint32_t ulHartId;

		__asm volatile( "csrr %0, mhartid" : "=r"( ulHartId ) );
		pullMachineTimerCompareRegister  = ( volatile uint64_t * ) ( ullMachineTimerCompareRegisterBase + ( ulHartId * sizeof( uint64_t ) ) );

		do
		{
			ulCurrentTimeHigh = *pulTimeHigh;
			ulCurrentTimeLow = *pulTimeLow;
		} while( ulCurrentTimeHigh != *pulTimeHigh );

		ullNextTime = ( uint64_t ) ulCurrentTimeHigh;
		ullNextTime <<= 32ULL; /* High 4-byte word is 32-bits up. */
		ullNextTime |= ( uint64_t ) ulCurrentTimeLow;
		ullNextTime += ( uint64_t ) uxTimerIncrementsForOneTick;
		*pullMachineTimerCompareRegister = ullNextTime;

		/* Prepare the time to use after the next tick interrupt. */
		ullNextTime += ( uint64_t ) uxTimerIncrementsForOneTick;
	}
#else  /*GAIGER*/
/* just for wch's systick,don't have mtime */
void vPortSetupTimerInterrupt( void )
{
    /* set software is lowest priority */
    NVIC_SetPriority(Software_IRQn,0xf0);
    NVIC_EnableIRQ(Software_IRQn);
    /* set systick is lowest priority */
    NVIC_SetPriority(SysTicK_IRQn,0xf0);
    NVIC_EnableIRQ(SysTicK_IRQn);

    SysTick->CTLR= 0;
    SysTick->SR  = 0;
    SysTick->CNT = 0;
    SysTick->CMP = configCPU_CLOCK_HZ/configTICK_RATE_HZ;
    SysTick->CTLR= 0xf;
}
#endif /* ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIME_BASE_ADDRESS != 0 ) */
/*-----------------------------------------------------------*/
#if(0)
BaseType_t xPortStartScheduler( void )
{
extern void xPortStartFirstTask( void );

	#if( configASSERT_DEFINED == 1 )
	{
		volatile uint32_t mtvec = 0;

		/* Check the least significant two bits of mtvec are 00 - indicating
		single vector mode. */
		__asm volatile( "csrr %0, mtvec" : "=r"( mtvec ) );
		configASSERT( ( mtvec & 0x03UL ) == 0 );

		/* Check alignment of the interrupt stack - which is the same as the
		stack that was being used by main() prior to the scheduler being
		started. */
		configASSERT( ( xISRStackTop & portBYTE_ALIGNMENT_MASK ) == 0 );

		#ifdef configISR_STACK_SIZE_WORDS
		{
			memset( ( void * ) xISRStack, portISR_STACK_FILL_BYTE, sizeof( xISRStack ) );
		}
		#endif	 /* configISR_STACK_SIZE_WORDS */
	}
	#endif /* configASSERT_DEFINED */

	/* If there is a CLINT then it is ok to use the default implementation
	in this file, otherwise vPortSetupTimerInterrupt() must be implemented to
	configure whichever clock is to be used to generate the tick interrupt. */
	vPortSetupTimerInterrupt();

	#if( ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 ) )
	{
		/* Enable mtime and external interrupts.  1<<7 for timer interrupt, 1<<11
		for external interrupt.  _RB_ What happens here when mtime is not present as
		with pulpino? */
		__asm volatile( "csrs mie, %0" :: "r"(0x880) );
	}
	#else
	{
		/* Enable external interrupts. */
		__asm volatile( "csrs mie, %0" :: "r"(0x800) );
	}
	#endif /* ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 ) */

	xPortStartFirstTask();

	/* Should not get here as after calling xPortStartFirstTask() only tasks
	should be executing. */
	return pdFAIL;
}
#else
BaseType_t xPortStartScheduler( void )
{
extern void xPortStartFirstTask( void );

	#if( configASSERT_DEFINED == 1 )
	{
		volatile uint32_t mtvec = 0;
		/* Check the least significant two bits of mtvec are 0b11 - indicating
		multiply vector mode. */
		__asm volatile( "csrr %0, mtvec" : "=r"( mtvec ) );
		configASSERT( ( mtvec & 0x03UL ) == 0x3 );
		/* Check alignment of the interrupt stack - which is the same as the
		stack that was being used by main() prior to the scheduler being
		started. */
		configASSERT( ( xISRStackTop & portBYTE_ALIGNMENT_MASK ) == 0 );

		#ifdef configISR_STACK_SIZE_WORDS
		{
			memset( ( void * ) xISRStack, portISR_STACK_FILL_BYTE, sizeof( xISRStack ) );
		}
		#endif	/* configISR_STACK_SIZE_WORDS */
	}
	#endif /* configASSERT_DEFINED */

	/* If there is a CLINT then it is ok to use the default implementation
	in this file, otherwise vPortSetupTimerInterrupt() must be implemented to
	configure whichever clock is to be used to generate the tick interrupt. */
	vPortSetupTimerInterrupt();

	#if( ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 ) )
	{
		/* Enable mtime and external interrupts.  1<<7 for timer interrupt, 1<<11
		for external interrupt.  _RB_ What happens here when mtime is not present as
		with pulpino? */
		__asm volatile( "csrw mstatus,%0" ::"r"(0x7880) );
	}
	#else
	{
		/* Enable external interrupts. */
		__asm volatile( "csrw mstatus,%0" ::"r"(0x7888) );
	}
	#endif /* ( configMTIME_BASE_ADDRESS != 0 ) && ( configMTIMECMP_BASE_ADDRESS != 0 ) */

	uxCriticalNesting = 0;
	xPortStartFirstTask();

	/* Should not get here as after calling xPortStartFirstTask() only tasks
	should be executing. */
	return pdFAIL;
}
#endif
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* Not implemented. */
	for( ;; );
}

#if(1) //GAIGER
/*-----------------------------------------------------------*/
void SysTick_Handler(void) __attribute__((interrupt("WCH-Interrupt-fast")));
void SysTick_Handler( void )
{
	GET_INT_SP();
	portDISABLE_INTERRUPTS();
	SysTick->SR=0;
	if( xTaskIncrementTick() != pdFALSE )
	{
		portYIELD();
	}
	portENABLE_INTERRUPTS();
	FREE_INT_SP();
}

/*-----------------------------------------------------------*/
void vPortEnterCritical( void )
{
	portDISABLE_INTERRUPTS();
	uxCriticalNesting++;
}

/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
	configASSERT( uxCriticalNesting );
	uxCriticalNesting--;

	if( uxCriticalNesting == 0 )
	{
		portENABLE_INTERRUPTS();
	}
}
/*-----------------------------------------------------------*/
portUBASE_TYPE xPortSetInterruptMask(void)
{
	portUBASE_TYPE uvalue=0;
	__asm volatile("csrrw %0, mstatus, %1":"=r"(uvalue):"r"(0x7800));
	return uvalue;
}

/*-----------------------------------------------------------*/
void vPortClearInterruptMask(portUBASE_TYPE uvalue)
{
	__asm volatile("csrw  mstatus, %0"::"r"(uvalue));
}
#endif

Modify the file FreeRTOS\Source\portable\GCC\RISC-V\portASM.S as : 

/*
 * FreeRTOS Kernel V10.4.6
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

/*
 * The FreeRTOS kernel's RISC-V port is split between the the code that is
 * common across all currently supported RISC-V chips (implementations of the
 * RISC-V ISA), and code which tailors the port to a specific RISC-V chip:
 *
 * + The code that is common to all RISC-V chips is implemented in
 *   FreeRTOS\Source\portable\GCC\RISC-V-RV32\portASM.S.  There is only one
 *   portASM.S file because the same file is used no matter which RISC-V chip is
 *   in use.
 *
 * + The code that tailors the kernel's RISC-V port to a specific RISC-V
 *   chip is implemented in freertos_risc_v_chip_specific_extensions.h.  There
 *   is one freertos_risc_v_chip_specific_extensions.h that can be used with any
 *   RISC-V chip that both includes a standard CLINT and does not add to the
 *   base set of RISC-V registers.  There are additional
 *   freertos_risc_v_chip_specific_extensions.h files for RISC-V implementations
 *   that do not include a standard CLINT or do add to the base set of RISC-V
 *   registers.
 *
 * CARE MUST BE TAKEN TO INCLDUE THE CORRECT
 * freertos_risc_v_chip_specific_extensions.h HEADER FILE FOR THE CHIP
 * IN USE.  To include the correct freertos_risc_v_chip_specific_extensions.h
 * header file ensure the path to the correct header file is in the assembler's
 * include path.
 *
 * This freertos_risc_v_chip_specific_extensions.h is for use on RISC-V chips
 * that include a standard CLINT and do not add to the base set of RISC-V
 * registers.
 *
 */
#if __riscv_xlen == 64
	#define portWORD_SIZE 8
	#define store_x sd
	#define load_x ld
#elif __riscv_xlen == 32
	#define store_x sw
	#define load_x lw
	#define portWORD_SIZE 4
#else
	#error Assembler did not define __riscv_xlen
#endif

#include "freertos_risc_v_chip_specific_extensions.h"

/* Check the freertos_risc_v_chip_specific_extensions.h and/or command line
definitions. */
#if defined( portasmHAS_CLINT ) && defined( portasmHAS_MTIME )
	#error The portasmHAS_CLINT constant has been deprecated.  Please replace it with portasmHAS_MTIME.  portasmHAS_CLINT and portasmHAS_MTIME cannot both be defined at once.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

#ifdef portasmHAS_CLINT
	#warning The portasmHAS_CLINT constant has been deprecated.  Please replace it with portasmHAS_MTIME and portasmHAS_SIFIVE_CLINT.  For now portasmHAS_MTIME and portasmHAS_SIFIVE_CLINT are derived from portasmHAS_CLINT.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
	#define portasmHAS_MTIME portasmHAS_CLINT
	#define portasmHAS_SIFIVE_CLINT portasmHAS_CLINT
#endif

#ifndef portasmHAS_MTIME
	#error freertos_risc_v_chip_specific_extensions.h must define portasmHAS_MTIME to either 1 (MTIME clock present) or 0 (MTIME clock not present).  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif

#ifndef portasmHANDLE_INTERRUPT
#if(0)//GAIGER
	#error portasmHANDLE_INTERRUPT must be defined to the function to be called to handle external/peripheral interrupts.  portasmHANDLE_INTERRUPT can be defined on the assembler command line or in the appropriate freertos_risc_v_chip_specific_extensions.h header file.  https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif
#endif

#ifndef portasmHAS_SIFIVE_CLINT
	#define portasmHAS_SIFIVE_CLINT 0
#endif

/* Only the standard core registers are stored by default.  Any additional
registers must be saved by the portasmSAVE_ADDITIONAL_REGISTERS and
portasmRESTORE_ADDITIONAL_REGISTERS macros - which can be defined in a chip
specific version of freertos_risc_v_chip_specific_extensions.h.  See the notes
at the top of this file. */

#if(1) //GAIGER
#define freertos_risc_v_trap_handler SW_Handler
#endif


#define portCONTEXT_SIZE ( 30 * portWORD_SIZE )

.global xPortStartFirstTask
.global freertos_risc_v_trap_handler
.global pxPortInitialiseStack
.extern pxCurrentTCB
.extern ulPortTrapHandler
.extern vTaskSwitchContext
.extern xTaskIncrementTick
.extern Timer_IRQHandler
.extern pullMachineTimerCompareRegister
.extern pullNextTime
.extern uxTimerIncrementsForOneTick /* size_t type so 32-bit on 32-bit core and 64-bits on 64-bit core. */
.extern xISRStackTop
.extern portasmHANDLE_INTERRUPT

/*-----------------------------------------------------------*/

.align 8
.func
freertos_risc_v_trap_handler:
	addi sp, sp, -portCONTEXT_SIZE
	store_x x1, 1 * portWORD_SIZE( sp )
	store_x x5, 2 * portWORD_SIZE( sp )
	store_x x6, 3 * portWORD_SIZE( sp )
	store_x x7, 4 * portWORD_SIZE( sp )
	store_x x8, 5 * portWORD_SIZE( sp )
	store_x x9, 6 * portWORD_SIZE( sp )
	store_x x10, 7 * portWORD_SIZE( sp )
	store_x x11, 8 * portWORD_SIZE( sp )
	store_x x12, 9 * portWORD_SIZE( sp )
	store_x x13, 10 * portWORD_SIZE( sp )
	store_x x14, 11 * portWORD_SIZE( sp )
	store_x x15, 12 * portWORD_SIZE( sp )
	store_x x16, 13 * portWORD_SIZE( sp )
	store_x x17, 14 * portWORD_SIZE( sp )
	store_x x18, 15 * portWORD_SIZE( sp )
	store_x x19, 16 * portWORD_SIZE( sp )
	store_x x20, 17 * portWORD_SIZE( sp )
	store_x x21, 18 * portWORD_SIZE( sp )
	store_x x22, 19 * portWORD_SIZE( sp )
	store_x x23, 20 * portWORD_SIZE( sp )
	store_x x24, 21 * portWORD_SIZE( sp )
	store_x x25, 22 * portWORD_SIZE( sp )
	store_x x26, 23 * portWORD_SIZE( sp )
	store_x x27, 24 * portWORD_SIZE( sp )
	store_x x28, 25 * portWORD_SIZE( sp )
	store_x x29, 26 * portWORD_SIZE( sp )
	store_x x30, 27 * portWORD_SIZE( sp )
	store_x x31, 28 * portWORD_SIZE( sp )

	csrr t0, mstatus					/* Required for MPIE bit. */
	store_x t0, 29 * portWORD_SIZE( sp )

	portasmSAVE_ADDITIONAL_REGISTERS	/* Defined in freertos_risc_v_chip_specific_extensions.h to save any registers unique to the RISC-V implementation. */

	load_x  t0, pxCurrentTCB			/* Load pxCurrentTCB. */
	store_x  sp, 0( t0 )				/* Write sp to first TCB member. */

#if(0)//GAIGER

	csrr a0, mcause
	csrr a1, mepc

test_if_asynchronous:
	srli a2, a0, __riscv_xlen - 1		/* MSB of mcause is 1 if handing an asynchronous interrupt - shift to LSB to clear other bits. */
	beq a2, x0, handle_synchronous		/* Branch past interrupt handing if not asynchronous. */
	store_x a1, 0( sp )					/* Asynch so save unmodified exception return address. */

handle_asynchronous:

#if( portasmHAS_MTIME != 0 )

	test_if_mtimer:						/* If there is a CLINT then the mtimer is used to generate the tick interrupt. */

		addi t0, x0, 1

		slli t0, t0, __riscv_xlen - 1   /* LSB is already set, shift into MSB.  Shift 31 on 32-bit or 63 on 64-bit cores. */
		addi t1, t0, 7					/* 0x8000[]0007 == machine timer interrupt. */
		bne a0, t1, test_if_external_interrupt

		load_x t0, pullMachineTimerCompareRegister  /* Load address of compare register into t0. */
		load_x t1, pullNextTime  		/* Load the address of ullNextTime into t1. */

		#if( __riscv_xlen == 32 )

			/* Update the 64-bit mtimer compare match value in two 32-bit writes. */
			li t4, -1
			lw t2, 0(t1)				/* Load the low word of ullNextTime into t2. */
			lw t3, 4(t1)				/* Load the high word of ullNextTime into t3. */
			sw t4, 0(t0)				/* Low word no smaller than old value to start with - will be overwritten below. */
			sw t3, 4(t0)				/* Store high word of ullNextTime into compare register.  No smaller than new value. */
			sw t2, 0(t0)				/* Store low word of ullNextTime into compare register. */
			lw t0, uxTimerIncrementsForOneTick	/* Load the value of ullTimerIncrementForOneTick into t0 (could this be optimized by storing in an array next to pullNextTime?). */
			add t4, t0, t2				/* Add the low word of ullNextTime to the timer increments for one tick (assumes timer increment for one tick fits in 32-bits). */
			sltu t5, t4, t2				/* See if the sum of low words overflowed (what about the zero case?). */
			add t6, t3, t5				/* Add overflow to high word of ullNextTime. */
			sw t4, 0(t1)				/* Store new low word of ullNextTime. */
			sw t6, 4(t1)				/* Store new high word of ullNextTime. */

		#endif /* __riscv_xlen == 32 */

		#if( __riscv_xlen == 64 )

			/* Update the 64-bit mtimer compare match value. */
			ld t2, 0(t1)			 	/* Load ullNextTime into t2. */
			sd t2, 0(t0)				/* Store ullNextTime into compare register. */
			ld t0, uxTimerIncrementsForOneTick  /* Load the value of ullTimerIncrementForOneTick into t0 (could this be optimized by storing in an array next to pullNextTime?). */
			add t4, t0, t2				/* Add ullNextTime to the timer increments for one tick. */
			sd t4, 0(t1)				/* Store ullNextTime. */

		#endif /* __riscv_xlen == 64 */

		load_x sp, xISRStackTop			/* Switch to ISR stack before function call. */
		jal xTaskIncrementTick
		beqz a0, processed_source		/* Don't switch context if incrementing tick didn't unblock a task. */
		jal vTaskSwitchContext
		j processed_source

	test_if_external_interrupt:			/* If there is a CLINT and the mtimer interrupt is not pending then check to see if an external interrupt is pending. */
		addi t1, t1, 4					/* 0x80000007 + 4 = 0x8000000b == Machine external interrupt. */
		bne a0, t1, as_yet_unhandled	/* Something as yet unhandled. */

#endif /* portasmHAS_MTIME */

	load_x sp, xISRStackTop				/* Switch to ISR stack before function call. */
	jal portasmHANDLE_INTERRUPT			/* Jump to the interrupt handler if there is no CLINT or if there is a CLINT and it has been determined that an external interrupt is pending. */
	j processed_source

handle_synchronous:
	addi a1, a1, 4						/* Synchronous so updated exception return address to the instruction after the instruction that generated the exeption. */
	store_x a1, 0( sp )					/* Save updated exception return address. */

test_if_environment_call:
	li t0, 11 							/* 11 == environment call. */
	bne a0, t0, is_exception			/* Not an M environment call, so some other exception. */
	load_x sp, xISRStackTop				/* Switch to ISR stack before function call. */
	jal vTaskSwitchContext
	j processed_source

is_exception:
	csrr t0, mcause						/* For viewing in the debugger only. */
	csrr t1, mepc						/* For viewing in the debugger only */
	csrr t2, mstatus
	j is_exception						/* No other exceptions handled yet. */

as_yet_unhandled:
	csrr t0, mcause						/* For viewing in the debugger only. */
	j as_yet_unhandled

#else
	csrr a1, mepc
	store_x a1, 0( sp )					/* Save updated exception return address. */

	addi a1, x0, 0x20
	csrs 0x804, a1

	load_x sp, xISRStackTop				/* Switch to ISR stack before function call. */
	jal vTaskSwitchContext
#endif

processed_source:
	load_x  t1, pxCurrentTCB			/* Load pxCurrentTCB. */
	load_x  sp, 0( t1 )				 	/* Read sp from first TCB member. */

	/* Load mret with the address of the next instruction in the task to run next. */
	load_x t0, 0( sp )
	csrw mepc, t0

	portasmRESTORE_ADDITIONAL_REGISTERS	/* Defined in freertos_risc_v_chip_specific_extensions.h to restore any registers unique to the RISC-V implementation. */

	/* Load mstatus with the interrupt enable bits used by the task. */
	load_x  t0, 29 * portWORD_SIZE( sp )
	csrw mstatus, t0						/* Required for MPIE bit. */

	load_x  x1, 1 * portWORD_SIZE( sp )
	load_x  x5, 2 * portWORD_SIZE( sp )		/* t0 */
	load_x  x6, 3 * portWORD_SIZE( sp )		/* t1 */
	load_x  x7, 4 * portWORD_SIZE( sp )		/* t2 */
	load_x  x8, 5 * portWORD_SIZE( sp )		/* s0/fp */
	load_x  x9, 6 * portWORD_SIZE( sp )		/* s1 */
	load_x  x10, 7 * portWORD_SIZE( sp )	/* a0 */
	load_x  x11, 8 * portWORD_SIZE( sp )	/* a1 */
	load_x  x12, 9 * portWORD_SIZE( sp )	/* a2 */
	load_x  x13, 10 * portWORD_SIZE( sp )	/* a3 */
	load_x  x14, 11 * portWORD_SIZE( sp )	/* a4 */
	load_x  x15, 12 * portWORD_SIZE( sp )	/* a5 */
	load_x  x16, 13 * portWORD_SIZE( sp )	/* a6 */
	load_x  x17, 14 * portWORD_SIZE( sp )	/* a7 */
	load_x  x18, 15 * portWORD_SIZE( sp )	/* s2 */
	load_x  x19, 16 * portWORD_SIZE( sp )	/* s3 */
	load_x  x20, 17 * portWORD_SIZE( sp )	/* s4 */
	load_x  x21, 18 * portWORD_SIZE( sp )	/* s5 */
	load_x  x22, 19 * portWORD_SIZE( sp )	/* s6 */
	load_x  x23, 20 * portWORD_SIZE( sp )	/* s7 */
	load_x  x24, 21 * portWORD_SIZE( sp )	/* s8 */
	load_x  x25, 22 * portWORD_SIZE( sp )	/* s9 */
	load_x  x26, 23 * portWORD_SIZE( sp )	/* s10 */
	load_x  x27, 24 * portWORD_SIZE( sp )	/* s11 */
	load_x  x28, 25 * portWORD_SIZE( sp )	/* t3 */
	load_x  x29, 26 * portWORD_SIZE( sp )	/* t4 */
	load_x  x30, 27 * portWORD_SIZE( sp )	/* t5 */
	load_x  x31, 28 * portWORD_SIZE( sp )	/* t6 */
	addi sp, sp, portCONTEXT_SIZE

	mret
	.endfunc
/*-----------------------------------------------------------*/

.align 8
.func
xPortStartFirstTask:

#if( portasmHAS_SIFIVE_CLINT != 0 )
	/* If there is a clint then interrupts can branch directly to the FreeRTOS
	trap handler.  Otherwise the interrupt controller will need to be configured
	outside of this file. */
	la t0, freertos_risc_v_trap_handler
	csrw mtvec, t0
#endif /* portasmHAS_CLILNT */

#if(1) //GAIGER
/* if it is an assembly entry code, the SP offset value is determined by the assembly code,
but the C code is determined by the compiler, so we subtract 512 here as a reservation.
When entering the interrupt function of C code, the compiler automatically presses the stack
into the task stack. We can only change the SP value used by the calling function after switching
the interrupt stack.This problem can be solved by modifying the interrupt to the assembly entry,
and there is no need to reserve 512 bytes. You only need to switch the interrupt stack at the
beginning of the interrupt function */
	lw t0, xISRStackTop
	addi t0, t0, -512
    csrw mscratch,t0
#endif

	load_x  sp, pxCurrentTCB			/* Load pxCurrentTCB. */
	load_x  sp, 0( sp )				 	/* Read sp from first TCB member. */

	load_x  x1, 0( sp ) /* Note for starting the scheduler the exception return address is used as the function return address. */

	portasmRESTORE_ADDITIONAL_REGISTERS	/* Defined in freertos_risc_v_chip_specific_extensions.h to restore any registers unique to the RISC-V implementation. */

	load_x  x6, 3 * portWORD_SIZE( sp )		/* t1 */
	load_x  x7, 4 * portWORD_SIZE( sp )		/* t2 */
	load_x  x8, 5 * portWORD_SIZE( sp )		/* s0/fp */
	load_x  x9, 6 * portWORD_SIZE( sp )		/* s1 */
	load_x  x10, 7 * portWORD_SIZE( sp )	/* a0 */
	load_x  x11, 8 * portWORD_SIZE( sp )	/* a1 */
	load_x  x12, 9 * portWORD_SIZE( sp )	/* a2 */
	load_x  x13, 10 * portWORD_SIZE( sp )	/* a3 */
	load_x  x14, 11 * portWORD_SIZE( sp )	/* a4 */
	load_x  x15, 12 * portWORD_SIZE( sp )	/* a5 */
	load_x  x16, 13 * portWORD_SIZE( sp )	/* a6 */
	load_x  x17, 14 * portWORD_SIZE( sp )	/* a7 */
	load_x  x18, 15 * portWORD_SIZE( sp )	/* s2 */
	load_x  x19, 16 * portWORD_SIZE( sp )	/* s3 */
	load_x  x20, 17 * portWORD_SIZE( sp )	/* s4 */
	load_x  x21, 18 * portWORD_SIZE( sp )	/* s5 */
	load_x  x22, 19 * portWORD_SIZE( sp )	/* s6 */
	load_x  x23, 20 * portWORD_SIZE( sp )	/* s7 */
	load_x  x24, 21 * portWORD_SIZE( sp )	/* s8 */
	load_x  x25, 22 * portWORD_SIZE( sp )	/* s9 */
	load_x  x26, 23 * portWORD_SIZE( sp )	/* s10 */
	load_x  x27, 24 * portWORD_SIZE( sp )	/* s11 */
	load_x  x28, 25 * portWORD_SIZE( sp )	/* t3 */
	load_x  x29, 26 * portWORD_SIZE( sp )	/* t4 */
	load_x  x30, 27 * portWORD_SIZE( sp )	/* t5 */
	load_x  x31, 28 * portWORD_SIZE( sp )	/* t6 */

	load_x  x5, 29 * portWORD_SIZE( sp )	/* Initial mstatus into x5 (t0) */
	addi x5, x5, 0x08						/* Set MIE bit so the first task starts with interrupts enabled - required as returns with ret not eret. */
	csrrw  x0, mstatus, x5					/* Interrupts enabled from here! */
	load_x  x5, 2 * portWORD_SIZE( sp )		/* Initial x5 (t0) value. */

	addi	sp, sp, portCONTEXT_SIZE
	ret
	.endfunc
/*-----------------------------------------------------------*/

/*
 * Unlike other ports pxPortInitialiseStack() is written in assembly code as it
 * needs access to the portasmADDITIONAL_CONTEXT_SIZE constant.  The prototype
 * for the function is as per the other ports:
 * StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters );
 *
 * As per the standard RISC-V ABI pxTopcOfStack is passed in in a0, pxCode in
 * a1, and pvParameters in a2.  The new top of stack is passed out in a0.
 *
 * RISC-V maps registers to ABI names as follows (X1 to X31 integer registers
 * for the 'I' profile, X1 to X15 for the 'E' profile, currently I assumed).
 *
 * Register		ABI Name	Description						Saver
 * x0			zero		Hard-wired zero					-
 * x1			ra			Return address					Caller
 * x2			sp			Stack pointer					Callee
 * x3			gp			Global pointer					-
 * x4			tp			Thread pointer					-
 * x5-7			t0-2		Temporaries						Caller
 * x8			s0/fp		Saved register/Frame pointer	Callee
 * x9			s1			Saved register					Callee
 * x10-11		a0-1		Function Arguments/return values Caller
 * x12-17		a2-7		Function arguments				Caller
 * x18-27		s2-11		Saved registers					Callee
 * x28-31		t3-6		Temporaries						Caller
 *
 * The RISC-V context is saved t FreeRTOS tasks in the following stack frame,
 * where the global and thread pointers are currently assumed to be constant so
 * are not saved:
 *
 * mstatus
 * x31
 * x30
 * x29
 * x28
 * x27
 * x26
 * x25
 * x24
 * x23
 * x22
 * x21
 * x20
 * x19
 * x18
 * x17
 * x16
 * x15
 * x14
 * x13
 * x12
 * x11
 * pvParameters
 * x9
 * x8
 * x7
 * x6
 * x5
 * portTASK_RETURN_ADDRESS
 * [chip specific registers go here]
 * pxCode
 */
.align 8
.func
pxPortInitialiseStack:

	csrr t0, mstatus					/* Obtain current mstatus value. */
	andi t0, t0, ~0x8					/* Ensure interrupts are disabled when the stack is restored within an ISR.  Required when a task is created after the schedulre has been started, otherwise interrupts would be disabled anyway. */
#if(0)/*GAIGER*/
	addi t1, x0, 0x188					/* Generate the value 0x1880, which are the MPIE and MPP bits to set in mstatus. */
#else
	addi t1, x0, 0x788 /*0x188 + 0x600, where the 0x600 is to enable the float*/
#endif
	slli t1, t1, 4
	or t0, t0, t1						/* Set MPIE and MPP bits in mstatus value. */

	addi a0, a0, -portWORD_SIZE
	store_x t0, 0(a0)					/* mstatus onto the stack. */
	addi a0, a0, -(22 * portWORD_SIZE)	/* Space for registers x11-x31. */
	store_x a2, 0(a0)					/* Task parameters (pvParameters parameter) goes into register X10/a0 on the stack. */
	addi a0, a0, -(6 * portWORD_SIZE)	/* Space for registers x5-x9. */
	store_x x0, 0(a0)					/* Return address onto the stack, could be portTASK_RETURN_ADDRESS */
	addi t0, x0, portasmADDITIONAL_CONTEXT_SIZE /* The number of chip specific additional registers. */
chip_specific_stack_frame:				/* First add any chip specific registers to the stack frame being created. */
	beq t0, x0, 1f						/* No more chip specific registers to save. */
	addi a0, a0, -portWORD_SIZE			/* Make space for chip specific register. */
	store_x x0, 0(a0)					/* Give the chip specific register an initial value of zero. */
	addi t0, t0, -1						/* Decrement the count of chip specific registers remaining. */
	j chip_specific_stack_frame			/* Until no more chip specific registers. */
1:
	addi a0, a0, -portWORD_SIZE
	store_x a1, 0(a0)					/* mret value (pxCode parameter) onto the stack. */
	ret
	.endfunc
/*-----------------------------------------------------------*/

Modify the file FreeRTOS\Source\portable\GCC\RISC-V\pportmacro.h as : 

/*
 * FreeRTOS Kernel V10.4.6
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */


#ifndef PORTMACRO_H
#define PORTMACRO_H

#ifdef __cplusplus
extern "C" {
#endif

/*-----------------------------------------------------------
 * Port specific definitions.
 *
 * The settings in this file configure FreeRTOS correctly for the
 * given hardware and compiler.
 *
 * These settings should not be altered.
 *-----------------------------------------------------------
 */

/* Type definitions. */
#if __riscv_xlen == 64
	#define portSTACK_TYPE			uint64_t
	#define portBASE_TYPE			int64_t
	#define portUBASE_TYPE			uint64_t
	#define portMAX_DELAY 			( TickType_t ) 0xffffffffffffffffUL
	#define portPOINTER_SIZE_TYPE 	uint64_t
#elif __riscv_xlen == 32
	#define portSTACK_TYPE	uint32_t
	#define portBASE_TYPE	int32_t
	#define portUBASE_TYPE	uint32_t
	#define portMAX_DELAY ( TickType_t ) 0xffffffffUL
#else
	#error Assembler did not define __riscv_xlen
#endif


typedef portSTACK_TYPE StackType_t;
typedef portBASE_TYPE BaseType_t;
typedef portUBASE_TYPE UBaseType_t;
typedef portUBASE_TYPE TickType_t;

/* Legacy type definitions. */
#define portCHAR		char
#define portFLOAT		float
#define portDOUBLE		double
#define portLONG		long
#define portSHORT		short

/* 32-bit tick type on a 32-bit architecture, so reads of the tick count do
not need to be guarded with a critical section. */
#define portTICK_TYPE_IS_ATOMIC 1
/*-----------------------------------------------------------*/

/* Architecture specifics. */
#define portSTACK_GROWTH			( -1 )
#define portTICK_PERIOD_MS			( ( TickType_t ) 1000 / configTICK_RATE_HZ )
#ifdef __riscv64
	#error This is the RV32 port that has not yet been adapted for 64.
	#define portBYTE_ALIGNMENT			16
#else
	#define portBYTE_ALIGNMENT			16
#endif
/*-----------------------------------------------------------*/


/* Scheduler utilities. */
extern void vTaskSwitchContext( void );
#if(0) //GAIGER
#define portYIELD() __asm volatile( "ecall" );
#else
#define portYIELD()   NVIC_SetPendingIRQ(Software_IRQn)
#endif
#define portEND_SWITCHING_ISR( xSwitchRequired ) do { if( xSwitchRequired ) vTaskSwitchContext(); } while( 0 )
#define portYIELD_FROM_ISR( x ) portEND_SWITCHING_ISR( x )
/*-----------------------------------------------------------*/


/* Critical section management. */
#if(0) //GAIGER
#define portCRITICAL_NESTING_IN_TCB					1
extern void vTaskEnterCritical( void );
extern void vTaskExitCritical( void );

#define portSET_INTERRUPT_MASK_FROM_ISR() 0
#define portCLEAR_INTERRUPT_MASK_FROM_ISR( uxSavedStatusValue ) ( void ) uxSavedStatusValue
#define portDISABLE_INTERRUPTS()	__asm volatile( "csrc mstatus, 8" )
#define portENABLE_INTERRUPTS()		__asm volatile( "csrs mstatus, 8" )
#define portENTER_CRITICAL()	vTaskEnterCritical()
#define portEXIT_CRITICAL()		vTaskExitCritical()
#else
extern void vPortEnterCritical( void );
extern void vPortExitCritical( void );
extern portUBASE_TYPE xPortSetInterruptMask(void);
extern void vPortClearInterruptMask(portUBASE_TYPE uvalue);
#define portSET_INTERRUPT_MASK_FROM_ISR()  xPortSetInterruptMask()
#define portCLEAR_INTERRUPT_MASK_FROM_ISR( uxSavedStatusValue )  vPortClearInterruptMask(uxSavedStatusValue)
#define portDISABLE_INTERRUPTS()    __asm volatile( "csrw mstatus,%0" ::"r"(0x7800) )
#define portENABLE_INTERRUPTS()     __asm volatile( "csrw mstatus,%0" ::"r"(0x7888) )
#define portENTER_CRITICAL()    vPortEnterCritical()
#define portEXIT_CRITICAL()     vPortExitCritical()

/* switch interrupt sp, sp is saved at first task switch. */
#define GET_INT_SP()   __asm volatile("csrrw sp,mscratch,sp")
#define FREE_INT_SP()  __asm volatile("csrrw sp,mscratch,sp")
#endif
/*-----------------------------------------------------------*/

/* Architecture specific optimisations. */
#ifndef configUSE_PORT_OPTIMISED_TASK_SELECTION
	#define configUSE_PORT_OPTIMISED_TASK_SELECTION 1
#endif

#if( configUSE_PORT_OPTIMISED_TASK_SELECTION == 1 )

	/* Check the configuration. */
	#if( configMAX_PRIORITIES > 32 )
		#error configUSE_PORT_OPTIMISED_TASK_SELECTION can only be set to 1 when configMAX_PRIORITIES is less than or equal to 32.  It is very rare that a system requires more than 10 to 15 difference priorities as tasks that share a priority will time slice.
	#endif

	/* Store/clear the ready priorities in a bit map. */
	#define portRECORD_READY_PRIORITY( uxPriority, uxReadyPriorities ) ( uxReadyPriorities ) |= ( 1UL << ( uxPriority ) )
	#define portRESET_READY_PRIORITY( uxPriority, uxReadyPriorities ) ( uxReadyPriorities ) &= ~( 1UL << ( uxPriority ) )

	/*-----------------------------------------------------------*/

	#define portGET_HIGHEST_PRIORITY( uxTopPriority, uxReadyPriorities ) uxTopPriority = ( 31UL - __builtin_clz( uxReadyPriorities ) )

#endif /* configUSE_PORT_OPTIMISED_TASK_SELECTION */


/*-----------------------------------------------------------*/

/* Task function macros as described on the FreeRTOS.org WEB site.  These are
not necessary for to use this port.  They are defined so the common demo files
(which build with all the ports) will build. */
#define portTASK_FUNCTION_PROTO( vFunction, pvParameters ) void vFunction( void *pvParameters )
#define portTASK_FUNCTION( vFunction, pvParameters ) void vFunction( void *pvParameters )

/*-----------------------------------------------------------*/

#define portNOP() __asm volatile 	( " nop " )

#define portINLINE	__inline

#ifndef portFORCE_INLINE
	#define portFORCE_INLINE inline __attribute__(( always_inline))
#endif

#define portMEMORY_BARRIER() __asm volatile( "" ::: "memory" )
/*-----------------------------------------------------------*/


/* configCLINT_BASE_ADDRESS is a legacy definition that was replaced by the
configMTIME_BASE_ADDRESS and configMTIMECMP_BASE_ADDRESS definitions.  For
backward compatibility derive the newer definitions from the old if the old
definition is found. */
#if defined( configCLINT_BASE_ADDRESS ) && !defined( configMTIME_BASE_ADDRESS ) && ( configCLINT_BASE_ADDRESS == 0 )
	/* Legacy case where configCLINT_BASE_ADDRESS was defined as 0 to indicate
	there was no CLINT.  Equivalent now is to set the MTIME and MTIMECMP
	addresses to 0. */
	#define configMTIME_BASE_ADDRESS 	( 0 )
	#define configMTIMECMP_BASE_ADDRESS ( 0 )
#elif defined( configCLINT_BASE_ADDRESS ) && !defined( configMTIME_BASE_ADDRESS )
	/* Legacy case where configCLINT_BASE_ADDRESS was set to the base address of
	the CLINT.  Equivalent now is to derive the MTIME and MTIMECMP addresses
	from the CLINT address. */
	#define configMTIME_BASE_ADDRESS 	( ( configCLINT_BASE_ADDRESS ) + 0xBFF8UL )
	#define configMTIMECMP_BASE_ADDRESS ( ( configCLINT_BASE_ADDRESS ) + 0x4000UL )
#elif !defined( configMTIME_BASE_ADDRESS ) || !defined( configMTIMECMP_BASE_ADDRESS )
	#error configMTIME_BASE_ADDRESS and configMTIMECMP_BASE_ADDRESS must be defined in FreeRTOSConfig.h.  Set them to zero if there is no MTIME (machine time) clock.  See https://www.FreeRTOS.org/Using-FreeRTOS-on-RISC-V.html
#endif



#ifdef __cplusplus
}
#endif

#endif /* PORTMACRO_H */

And the main.cpp, at the User folder :

/********************************** (C) COPYRIGHT *******************************
* File Name          : main.c
* Author             : WCH
* Version            : V1.0.0
* Date               : 2021/06/06
* Description        : Main program body.
* Copyright (c) 2021 Nanjing Qinheng Microelectronics Co., Ltd.
* SPDX-License-Identifier: Apache-2.0
*******************************************************************************/

/*
 *@Note
 task1 and task2 alternate printing
*/

#include "debug.h"
#include "FreeRTOS.h"
#include "task.h"
#include "semphr.h"

/* Global define */
#define TASK1_TASK_PRIO     5
#define TASK1_STK_SIZE      256
#define TASK2_TASK_PRIO     5
#define TASK2_STK_SIZE      256

/* Global Variable */
TaskHandle_t Task1Task_Handler;
TaskHandle_t Task2Task_Handler;

SemaphoreHandle_t g_mutex;

/*********************************************************************
 * @fn      GPIO_Toggle_INIT
 *
 * @brief   Initializes GPIOA.0/1
 *
 * @return  none
 */
void GPIO_Toggle_INIT(void)
{
    GPIO_InitTypeDef  GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOE,ENABLE);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11 | GPIO_Pin_12;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
    GPIO_Init(GPIOE, &GPIO_InitStructure);
}


/*********************************************************************
 * @fn      task1_task
 *
 * @brief   task1 program.
 *
 * @param  *pvParameters - Parameters point of task1
 *
 * @return  none
 */
void task1_task(void *pvParameters)
{
    uint32_t ii = 0;
    while(1)
    {
        xSemaphoreTake(g_mutex, portMAX_DELAY);
        printf("ch32v307_FreeRTOS task1 entry, %u\r\n", ii++);
        xSemaphoreGive(g_mutex);

        const TickType_t task1_delay = 250 / portTICK_PERIOD_MS;
        GPIO_SetBits(GPIOE, GPIO_Pin_11);
        vTaskDelay(task1_delay);
        GPIO_ResetBits(GPIOE, GPIO_Pin_11);
        vTaskDelay(task1_delay);
    }
}

/*********************************************************************
 * @fn      task2_task
 *
 * @brief   task2 program.
 *
 * @param  *pvParameters - Parameters point of task2
 *
 * @return  none
 */
void task2_task(void *pvParameters)
{
    uint32_t ii = 0;
    while(1)
    {
        xSemaphoreTake(g_mutex, portMAX_DELAY);
        printf("ch32v307_FreeRTOS task2 entry, %u\r\n", ii++);
        xSemaphoreGive(g_mutex);

        GPIO_ResetBits(GPIOE, GPIO_Pin_12);
        const TickType_t task2_delay = 500 / portTICK_PERIOD_MS;

        vTaskDelay(task2_delay);
        GPIO_SetBits(GPIOE, GPIO_Pin_12);
        vTaskDelay(task2_delay);
    }
}

/*********************************************************************
 * @fn      main
 *
 * @brief   Main program.
 *
 * @return  none
 */
int main(void)
{
    g_mutex = xSemaphoreCreateMutex();

    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
    Delay_Init();
    USART_Printf_Init(115200);
    printf("SystemClk:%d\r\n",SystemCoreClock);
    printf("FreeRTOS Kernel Version:%s\r\n",tskKERNEL_VERSION_NUMBER);

    GPIO_Toggle_INIT();
    /* create two task */
    xTaskCreate((TaskFunction_t )task2_task,
                        (const char*    )"task2",
                        (uint16_t       )TASK2_STK_SIZE,
                        (void*          )NULL,
                        (UBaseType_t    )TASK2_TASK_PRIO,
                        (TaskHandle_t*  )&Task2Task_Handler);

    xTaskCreate((TaskFunction_t )task1_task,
                    (const char*    )"task1",
                    (uint16_t       )TASK1_STK_SIZE,
                    (void*          )NULL,
                    (UBaseType_t    )TASK1_TASK_PRIO,
                    (TaskHandle_t*  )&Task1Task_Handler);
    vTaskStartScheduler();

    while(1)
    {
        printf("shouldn't run at here!!\n");
    }
}

※ it may be necessary to modify the .cproject file , about line 51 , the field:

..option.assembler.usepreprocessor" useByScannerDiscovery="false" value="false" valueType="boolean"/>

change value = "false" to value = "true". 

To pass the compilation.

※ I use UART2 as my debug port, thus I change the definition as Debug/debug.h, line 24 :

:
/* DEBUG UATR Definition */
//#define DEBUG   DEBUG_UART1
#define DEBUG   DEBUG_UART2
//#define DEBUG   DEBUG_UART3


void Delay_Init(void);
:

四 . build and download the binary to the board, and it works.

五. How it works :

Be aware of the last lines at Startup\startup_ch32v30x_D8C.S

    ori t0, t0, 3           
    csrw mtvec, t0

    jal  SystemInit
    la t0, main
    csrw mepc, t0
    mret

It is, set mtvect as 3, it is vectored-interrupt mode; after calling SystemInit, (load main function address to mepc,) and return from machine mode to run main. It is, it switches into the user mode.

While it is user mode, it is permission denied to use the ecall instruction, thus WCH use the software-interrupt to achieve the calling of freertos_risc_v_trap_handler, which deals with the context-switch.

The timer to support FreeRTOS running, here is SysTimer, here the setting is straightforward than the default implementation.

Reference :

Solve Error: illegal operands `addi sp,sp,-portCONTEXT_SIZE'.  https://www.wch.cn/bbs/thread-87287-1.html