/* * FreeRTOS Kernel V10.5.1 * 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. * */ #include "portContext.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 portasmHAS_SIFIVE_CLINT #define portasmHAS_SIFIVE_CLINT 0 #endif .global xPortStartFirstTask .global pxPortInitialiseStack .global freertos_risc_v_trap_handler .global freertos_risc_v_exception_handler .global freertos_risc_v_interrupt_handler .global freertos_risc_v_mtimer_interrupt_handler .extern vTaskSwitchContext .extern xTaskIncrementTick .extern pullMachineTimerCompareRegister .extern pullNextTime .extern uxTimerIncrementsForOneTick /* size_t type so 32-bit on 32-bit core and 64-bits on 64-bit core. */ .extern xTaskReturnAddress .weak freertos_risc_v_application_exception_handler .weak freertos_risc_v_application_interrupt_handler /*-----------------------------------------------------------*/ .macro portUPDATE_MTIMER_COMPARE_REGISTER load_x a0, pullMachineTimerCompareRegister /* Load address of compare register into a0. */ load_x a1, pullNextTime /* Load the address of ullNextTime into a1. */ #if( __riscv_xlen == 32 ) /* Update the 64-bit mtimer compare match value in two 32-bit writes. */ li a4, -1 lw a2, 0(a1) /* Load the low word of ullNextTime into a2. */ lw a3, 4(a1) /* Load the high word of ullNextTime into a3. */ sw a4, 0(a0) /* Low word no smaller than old value to start with - will be overwritten below. */ sw a3, 4(a0) /* Store high word of ullNextTime into compare register. No smaller than new value. */ sw a2, 0(a0) /* 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 a4, t0, a2 /* Add the low word of ullNextTime to the timer increments for one tick (assumes timer increment for one tick fits in 32-bits). */ sltu t1, a4, a2 /* See if the sum of low words overflowed (what about the zero case?). */ add t2, a3, t1 /* Add overflow to high word of ullNextTime. */ sw a4, 0(a1) /* Store new low word of ullNextTime. */ sw t2, 4(a1) /* 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(a1) /* Load ullNextTime into t2. */ sd t2, 0(a0) /* 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(a1) /* Store ullNextTime. */ #endif /* __riscv_xlen == 64 */ .endm /*-----------------------------------------------------------*/ /* * 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 * xCriticalNesting * 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 */ 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. */ addi t1, x0, 0x188 /* Generate the value 0x1880, which are the MPIE and MPP bits to set in mstatus. */ 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, -portWORD_SIZE /* Space for critical nesting count. */ store_x x0, 0(a0) /* Critical nesting count starts at 0 for every task. */ #ifdef __riscv_32e addi a0, a0, -(6 * portWORD_SIZE) /* Space for registers x11-x15. */ #else addi a0, a0, -(22 * portWORD_SIZE) /* Space for registers x11-x31. */ #endif 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. */ load_x t0, xTaskReturnAddress store_x t0, 0(a0) /* Return address onto the stack. */ 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 /*-----------------------------------------------------------*/ xPortStartFirstTask: 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 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 */ #ifndef __riscv_32e 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 */ #endif load_x x5, portCRITICAL_NESTING_OFFSET * portWORD_SIZE( sp ) /* Obtain xCriticalNesting value for this task from task's stack. */ load_x x6, pxCriticalNesting /* Load the address of xCriticalNesting into x6. */ store_x x5, 0( x6 ) /* Restore the critical nesting value for this task. */ load_x x5, portMSTATUS_OFFSET * 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. */ load_x x6, 3 * portWORD_SIZE( sp ) /* Initial x6 (t1) value. */ addi sp, sp, portCONTEXT_SIZE ret /*-----------------------------------------------------------*/ freertos_risc_v_application_exception_handler: csrr t0, mcause /* For viewing in the debugger only. */ csrr t1, mepc /* For viewing in the debugger only */ csrr t2, mstatus /* For viewing in the debugger only */ j . /*-----------------------------------------------------------*/ freertos_risc_v_application_interrupt_handler: csrr t0, mcause /* For viewing in the debugger only. */ csrr t1, mepc /* For viewing in the debugger only */ csrr t2, mstatus /* For viewing in the debugger only */ j . /*-----------------------------------------------------------*/ .section .text.freertos_risc_v_exception_handler freertos_risc_v_exception_handler: portcontextSAVE_EXCEPTION_CONTEXT /* a0 now contains mcause. */ li t0, 11 /* 11 == environment call. */ bne a0, t0, other_exception /* Not an M environment call, so some other exception. */ call vTaskSwitchContext portcontextRESTORE_CONTEXT other_exception: call freertos_risc_v_application_exception_handler portcontextRESTORE_CONTEXT /*-----------------------------------------------------------*/ .section .text.freertos_risc_v_interrupt_handler freertos_risc_v_interrupt_handler: portcontextSAVE_INTERRUPT_CONTEXT call freertos_risc_v_application_interrupt_handler portcontextRESTORE_CONTEXT /*-----------------------------------------------------------*/ .section .text.freertos_risc_v_mtimer_interrupt_handler freertos_risc_v_mtimer_interrupt_handler: portcontextSAVE_INTERRUPT_CONTEXT portUPDATE_MTIMER_COMPARE_REGISTER call xTaskIncrementTick beqz a0, exit_without_context_switch /* Don't switch context if incrementing tick didn't unblock a task. */ call vTaskSwitchContext exit_without_context_switch: portcontextRESTORE_CONTEXT /*-----------------------------------------------------------*/ .section .text.freertos_risc_v_trap_handler .align 8 freertos_risc_v_trap_handler: portcontextSAVE_CONTEXT_INTERNAL csrr a0, mcause csrr a1, mepc bge a0, x0, synchronous_exception asynchronous_interrupt: store_x a1, 0( sp ) /* Asynchronous interrupt so save unmodified exception return address. */ load_x sp, xISRStackTop /* Switch to ISR stack. */ j handle_interrupt synchronous_exception: addi a1, a1, 4 /* Synchronous so update exception return address to the instruction after the instruction that generated the exeption. */ store_x a1, 0( sp ) /* Save updated exception return address. */ load_x sp, xISRStackTop /* Switch to ISR stack. */ j handle_exception handle_interrupt: #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, application_interrupt_handler portUPDATE_MTIMER_COMPARE_REGISTER call xTaskIncrementTick beqz a0, processed_source /* Don't switch context if incrementing tick didn't unblock a task. */ call vTaskSwitchContext j processed_source #endif /* portasmHAS_MTIME */ application_interrupt_handler: call freertos_risc_v_application_interrupt_handler j processed_source handle_exception: /* a0 contains mcause. */ li t0, 11 /* 11 == environment call. */ bne a0, t0, application_exception_handler /* Not an M environment call, so some other exception. */ call vTaskSwitchContext j processed_source application_exception_handler: call freertos_risc_v_application_exception_handler j processed_source /* No other exceptions handled yet. */ processed_source: portcontextRESTORE_CONTEXT /*-----------------------------------------------------------*/