esp-idf/components/freertos/FreeRTOS-Kernel/portable/riscv/port.c

/*
 * SPDX-FileCopyrightText: 2020 Amazon.com, Inc. or its affiliates
 *
 * SPDX-License-Identifier: MIT
 *
 * SPDX-FileContributor: 2016-2022 Espressif Systems (Shanghai) CO LTD
 */
/*
 * FreeRTOS Kernel V10.4.3
 * 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
 *
 * 1 tab == 4 spaces!
 */

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

#include "sdkconfig.h"
#include <string.h>
#include "soc/soc_caps.h"
#include "soc/periph_defs.h"
#include "soc/system_reg.h"
#include "hal/systimer_hal.h"
#include "hal/systimer_ll.h"
#include "riscv/rvruntime-frames.h"
#include "riscv/rv_utils.h"
#include "riscv/interrupt.h"
#include "esp_private/crosscore_int.h"
#include "esp_attr.h"
#include "esp_system.h"
#include "esp_intr_alloc.h"
#include "esp_log.h"
#include "FreeRTOS.h"       /* This pulls in portmacro.h */
#include "task.h"
#include "portmacro.h"
#include "port_systick.h"
#include "esp_memory_utils.h"

_Static_assert(portBYTE_ALIGNMENT == 16, "portBYTE_ALIGNMENT must be set to 16");

/* ---------------------------------------------------- Variables ------------------------------------------------------
 *
 * ------------------------------------------------------------------------------------------------------------------ */

/**
 * @brief A variable is used to keep track of the critical section nesting.
 * @note This variable has to be stored as part of the task context and must be initialized to a non zero value
 *       to ensure interrupts don't inadvertently become unmasked before the scheduler starts.
 *       As it is stored as part of the task context it will automatically be set to 0 when the first task is started.
 */
static UBaseType_t uxCriticalNesting = 0;
static UBaseType_t uxSavedInterruptState = 0;
BaseType_t uxSchedulerRunning = 0;  // Duplicate of xSchedulerRunning, accessible to port files
UBaseType_t uxInterruptNesting = 0;
BaseType_t xPortSwitchFlag = 0;
__attribute__((aligned(16))) static StackType_t xIsrStack[configISR_STACK_SIZE];
StackType_t *xIsrStackTop = &xIsrStack[0] + (configISR_STACK_SIZE & (~((portPOINTER_SIZE_TYPE)portBYTE_ALIGNMENT_MASK)));



/* ------------------------------------------------ FreeRTOS Portable --------------------------------------------------
 * - Provides implementation for functions required by FreeRTOS
 * - Declared in portable.h
 * ------------------------------------------------------------------------------------------------------------------ */

// ----------------- Scheduler Start/End -------------------

BaseType_t xPortStartScheduler(void)
{
    uxInterruptNesting = 0;
    uxCriticalNesting = 0;
    uxSchedulerRunning = 0;

    /* Setup the hardware to generate the tick. */
    vPortSetupTimer();

    esprv_intc_int_set_threshold(1); /* set global INTC masking level */
    rv_utils_intr_global_enable();

    vPortYield();

    /*Should not get here*/
    return pdFALSE;
}

void vPortEndScheduler(void)
{
    /* very unlikely this function will be called, so just trap here */
    abort();
}

// ------------------------ Stack --------------------------

/**
 * @brief Align stack pointer in a downward growing stack
 *
 * This macro is used to round a stack pointer downwards to the nearest n-byte boundary, where n is a power of 2.
 * This macro is generally used when allocating aligned areas on a downward growing stack.
 */
#define STACKPTR_ALIGN_DOWN(n, ptr)     ((ptr) & (~((n)-1)))

/**
 * @brief Allocate and initialize GCC TLS area
 *
 * This function allocates and initializes the area on the stack used to store GCC TLS (Thread Local Storage) variables.
 * - The area's size is derived from the TLS section's linker variables, and rounded up to a multiple of 16 bytes
 * - The allocated area is aligned to a 16-byte aligned address
 * - The TLS variables in the area are then initialized
 *
 * Each task access the TLS variables using the THREADPTR register plus an offset to obtain the address of the variable.
 * The value for the THREADPTR register is also calculated by this function, and that value should be use to initialize
 * the THREADPTR register.
 *
 * @param[in] uxStackPointer Current stack pointer address
 * @param[out] ret_threadptr_reg_init Calculated THREADPTR register initialization value
 * @return Stack pointer that points to the TLS area
 */
FORCE_INLINE_ATTR UBaseType_t uxInitialiseStackTLS(UBaseType_t uxStackPointer, uint32_t *ret_threadptr_reg_init)
{
    /*
    TLS layout at link-time, where 0xNNN is the offset that the linker calculates to a particular TLS variable.

    LOW ADDRESS
            |---------------------------|   Linker Symbols
            | Section                   |   --------------
            | .flash.rodata             |
         0x0|---------------------------| <- _flash_rodata_start
          ^ | Other Data                |
          | |---------------------------| <- _thread_local_start
          | | .tbss                     | ^
          V |                           | |
      0xNNN | int example;              | | tls_area_size
            |                           | |
            | .tdata                    | V
            |---------------------------| <- _thread_local_end
            | Other data                |
            | ...                       |
            |---------------------------|
    HIGH ADDRESS
    */
    // Calculate TLS area size and round up to multiple of 16 bytes.
    extern char _thread_local_start, _thread_local_end, _flash_rodata_start;
    const uint32_t tls_area_size = ALIGNUP(16, (uint32_t)&_thread_local_end - (uint32_t)&_thread_local_start);
    // TODO: check that TLS area fits the stack

    // Allocate space for the TLS area on the stack. The area must be aligned to 16-bytes
    uxStackPointer = STACKPTR_ALIGN_DOWN(16, uxStackPointer - (UBaseType_t)tls_area_size);
    // Initialize the TLS area with the initialization values of each TLS variable
    memcpy((void *)uxStackPointer, &_thread_local_start, tls_area_size);

    /*
    Calculate the THREADPTR register's initialization value based on the link-time offset and the TLS area allocated on
    the stack.

    HIGH ADDRESS
            |---------------------------|
            | .tdata (*)                |
          ^ | int example;              |
          | |                           |
          | | .tbss (*)                 |
          | |---------------------------| <- uxStackPointer (start of TLS area)
    0xNNN | |                           | ^
          | |                           | |
          |             ...               | _thread_local_start - _rodata_start
          | |                           | |
          | |                           | V
          V |                           | <- threadptr register's value

    LOW ADDRESS
    */
    *ret_threadptr_reg_init = (uint32_t)uxStackPointer - ((uint32_t)&_thread_local_start - (uint32_t)&_flash_rodata_start);
    return uxStackPointer;
}

#if CONFIG_FREERTOS_TASK_FUNCTION_WRAPPER
/**
 * Wrapper to allow task functions to return. Force the optimization option -O1 on that function to make sure there
 * is no tail-call. Indeed, we need the compiler to keep the return address to this function when calling `panic_abort`.
 *
 * Thanks to `naked` attribute, the compiler won't generate a prologue and epilogue for the function, which saves time
 * and stack space.
 */
static void __attribute__((optimize("O1"), naked)) vPortTaskWrapper(TaskFunction_t pxCode, void *pvParameters)
{
#ifdef __clang__
    // clang generates error "error: non-ASM statement in naked function is not supported"
    // The reason for it is described at
    // https://stackoverflow.com/questions/47316611/clang-error-non-asm-statement-in-naked-function-is-not-supported.
    // GCC docs say that there is no guarantee that non-ASM statement in naked function will work:
    // "Only basic asm statements can safely be included in naked functions (see Basic Asm).
    //  While using extended asm or a mixture of basic asm and C code may appear to work, they cannot be
    //  depended upon to work reliably and are not supported."
    // TODO: IDF-6347
    #error CONFIG_FREERTOS_TASK_FUNCTION_WRAPPER not supported yet when building with Clang!
#else
    asm volatile(".cfi_undefined ra\n");
    extern void __attribute__((noreturn)) panic_abort(const char *details);
    static char DRAM_ATTR msg[80] = "FreeRTOS: FreeRTOS Task \"\0";
    pxCode(pvParameters);
    //FreeRTOS tasks should not return. Log the task name and abort.
    char *pcTaskName = pcTaskGetName(NULL);
    /* We cannot use s(n)printf because it is in flash */
    strcat(msg, pcTaskName);
    strcat(msg, "\" should not return, Aborting now!");
    panic_abort(msg);
#endif
}
#endif // CONFIG_FREERTOS_TASK_FUNCTION_WRAPPER

/**
 * @brief Initialize the task's starting interrupt stack frame
 *
 * This function initializes the task's starting interrupt stack frame. The dispatcher will use this stack frame in a
 * context restore routine. Therefore, the starting stack frame must be initialized as if the task was interrupted right
 * before its first instruction is called.
 *
 * - The stack frame is allocated to a 16-byte aligned address
 *
 * @param[in] uxStackPointer Current stack pointer address
 * @param[in] pxCode Task function
 * @param[in] pvParameters Task function's parameter
 * @param[in] threadptr_reg_init THREADPTR register initialization value
 * @return Stack pointer that points to the stack frame
 */
FORCE_INLINE_ATTR UBaseType_t uxInitialiseStackFrame(UBaseType_t uxStackPointer, TaskFunction_t pxCode, void *pvParameters, uint32_t threadptr_reg_init)
{
    /*
    Allocate space for the task's starting interrupt stack frame.
    - The stack frame must be allocated to a 16-byte aligned address.
    - We use XT_STK_FRMSZ (instead of sizeof(XtExcFrame)) as it rounds up the total size to a multiple of 16.
    */
    uxStackPointer = STACKPTR_ALIGN_DOWN(16, uxStackPointer - RV_STK_FRMSZ);

    // Clear the entire interrupt stack frame
    RvExcFrame *frame = (RvExcFrame *)uxStackPointer;
    memset(frame, 0, sizeof(RvExcFrame));

    /* Initialize the stack frame. */
    extern uint32_t __global_pointer$;
    #if CONFIG_FREERTOS_TASK_FUNCTION_WRAPPER
        frame->mepc = (UBaseType_t)vPortTaskWrapper;
        frame->a0 = (UBaseType_t)pxCode;
        frame->a1 = (UBaseType_t)pvParameters;
    #else
        frame->mepc = (UBaseType_t)pxCode;
        frame->a0 = (UBaseType_t)pvParameters;
    #endif // CONFIG_FREERTOS_TASK_FUNCTION_WRAPPER
    frame->gp = (UBaseType_t)&__global_pointer$;
    frame->tp = (UBaseType_t)threadptr_reg_init;

    return uxStackPointer;
}

StackType_t *pxPortInitialiseStack(StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters)
{
    /*
    HIGH ADDRESS
    |---------------------------| <- pxTopOfStack on entry
    | TLS Variables             |
    | ------------------------- | <- Start of useable stack
    | Starting stack frame      |
    | ------------------------- | <- pxTopOfStack on return (which is the tasks current SP)
    |             |             |
    |             |             |
    |             V             |
    ----------------------------- <- Bottom of stack
    LOW ADDRESS

    - All stack areas are aligned to 16 byte boundary
    - We use UBaseType_t for all of stack area initialization functions for more convenient pointer arithmetic
    */

    UBaseType_t uxStackPointer = (UBaseType_t)pxTopOfStack;
    configASSERT((uxStackPointer & portBYTE_ALIGNMENT_MASK) == 0);

    // Initialize GCC TLS area
    uint32_t threadptr_reg_init;
    uxStackPointer = uxInitialiseStackTLS(uxStackPointer, &threadptr_reg_init);
    configASSERT((uxStackPointer & portBYTE_ALIGNMENT_MASK) == 0);

    // Initialize the starting interrupt stack frame
    uxStackPointer = uxInitialiseStackFrame(uxStackPointer, pxCode, pvParameters, threadptr_reg_init);
    configASSERT((uxStackPointer & portBYTE_ALIGNMENT_MASK) == 0);

    // Return the task's current stack pointer address which should point to the starting interrupt stack frame
    return (StackType_t *)uxStackPointer;
    //TODO: IDF-2393
}



/* ---------------------------------------------- Port Implementations -------------------------------------------------
 *
 * ------------------------------------------------------------------------------------------------------------------ */

// --------------------- Interrupts ------------------------

BaseType_t xPortInIsrContext(void)
{
    return uxInterruptNesting;
}

BaseType_t IRAM_ATTR xPortInterruptedFromISRContext(void)
{
    /* For single core, this can be the same as xPortInIsrContext() because reading it is atomic */
    return uxInterruptNesting;
}

// ---------------------- Spinlocks ------------------------



// ------------------ Critical Sections --------------------

void vPortEnterCritical(void)
{
    BaseType_t state = portSET_INTERRUPT_MASK_FROM_ISR();
    uxCriticalNesting++;

    if (uxCriticalNesting == 1) {
        uxSavedInterruptState = state;
    }
}

void vPortExitCritical(void)
{
    if (uxCriticalNesting > 0) {
        uxCriticalNesting--;
        if (uxCriticalNesting == 0) {
            portCLEAR_INTERRUPT_MASK_FROM_ISR(uxSavedInterruptState);
        }
    }
}

// ---------------------- Yielding -------------------------

int vPortSetInterruptMask(void)
{
    int ret;
    unsigned old_mstatus = RV_CLEAR_CSR(mstatus, MSTATUS_MIE);
    ret = REG_READ(INTERRUPT_CORE0_CPU_INT_THRESH_REG);
    REG_WRITE(INTERRUPT_CORE0_CPU_INT_THRESH_REG, RVHAL_EXCM_LEVEL);
    RV_SET_CSR(mstatus, old_mstatus & MSTATUS_MIE);
    /**
     * In theory, this function should not return immediately as there is a
     * delay between the moment we mask the interrupt threshold register and
     * the moment a potential lower-priority interrupt is triggered (as said
     * above), it should have a delay of 2 machine cycles/instructions.
     *
     * However, in practice, this function has an epilogue of one instruction,
     * thus the instruction masking the interrupt threshold register is
     * followed by two instructions: `ret` and `csrrs` (RV_SET_CSR).
     * That's why we don't need any additional nop instructions here.
     */
    return ret;
}

void vPortClearInterruptMask(int mask)
{
    REG_WRITE(INTERRUPT_CORE0_CPU_INT_THRESH_REG, mask);
    /**
     * The delay between the moment we unmask the interrupt threshold register
     * and the moment the potential requested interrupt is triggered is not
     * null: up to three machine cycles/instructions can be executed.
     *
     * When compilation size optimization is enabled, this function and its
     * callers returning void will have NO epilogue, thus the instruction
     * following these calls will be executed.
     *
     * If the requested interrupt is a context switch to a higher priority
     * task then the one currently running, we MUST NOT execute any instruction
     * before the interrupt effectively happens.
     * In order to prevent this, force this routine to have a 3-instruction
     * delay before exiting.
     */
    asm volatile ( "nop" );
    asm volatile ( "nop" );
    asm volatile ( "nop" );
}

void vPortYield(void)
{
    if (uxInterruptNesting) {
        vPortYieldFromISR();
    } else {

        esp_crosscore_int_send_yield(0);
        /* There are 3-4 instructions of latency between triggering the software
           interrupt and the CPU interrupt happening. Make sure it happened before
           we return, otherwise vTaskDelay() may return and execute 1-2
           instructions before the delay actually happens.

           (We could use the WFI instruction here, but there is a chance that
           the interrupt will happen while evaluating the other two conditions
           for an instant yield, and if that happens then the WFI would be
           waiting for the next interrupt to occur...)
        */
        while (uxSchedulerRunning && uxCriticalNesting == 0 && REG_READ(SYSTEM_CPU_INTR_FROM_CPU_0_REG) != 0) {}
    }
}

void vPortYieldFromISR( void )
{
    traceISR_EXIT_TO_SCHEDULER();
    uxSchedulerRunning = 1;
    xPortSwitchFlag = 1;
}

void vPortYieldOtherCore(BaseType_t coreid)
{
    esp_crosscore_int_send_yield(coreid);
}

// ------------------- Hook Functions ----------------------

void __attribute__((weak)) vApplicationStackOverflowHook(TaskHandle_t xTask, char *pcTaskName)
{
#define ERR_STR1 "***ERROR*** A stack overflow in task "
#define ERR_STR2 " has been detected."
    const char *str[] = {ERR_STR1, pcTaskName, ERR_STR2};

    char buf[sizeof(ERR_STR1) + CONFIG_FREERTOS_MAX_TASK_NAME_LEN + sizeof(ERR_STR2) + 1 /* null char */] = {0};

    char *dest = buf;
    for (int i = 0; i < sizeof(str) / sizeof(str[0]); i++) {
        dest = strcat(dest, str[i]);
    }
    esp_system_abort(buf);
}

// ----------------------- System --------------------------

uint32_t xPortGetTickRateHz(void)
{
    return (uint32_t)configTICK_RATE_HZ;
}

#define STACK_WATCH_AREA_SIZE 32
#define STACK_WATCH_POINT_NUMBER (SOC_CPU_WATCHPOINTS_NUM - 1)

void vPortSetStackWatchpoint(void *pxStackStart)
{
    uint32_t addr = (uint32_t)pxStackStart;
    addr = (addr + (STACK_WATCH_AREA_SIZE - 1)) & (~(STACK_WATCH_AREA_SIZE - 1));
    esp_cpu_set_watchpoint(STACK_WATCH_POINT_NUMBER, (char *)addr, STACK_WATCH_AREA_SIZE, ESP_CPU_WATCHPOINT_STORE);
}



/* ---------------------------------------------- Misc Implementations -------------------------------------------------
 *
 * ------------------------------------------------------------------------------------------------------------------ */