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fix(freertos): workaround a hardware bug related to HWLP coprocessor

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This commit manually sets the HWLP context to dirty when a Task that needs it is scheduled it.
This commit is contained in:
Omar Chebib
2025-02-18 11:57:10 +08:00
parent 46847b7be9
commit c26879d29e
4 changed files with 108 additions and 86 deletions
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177
components/freertos/FreeRTOS-Kernel/portable/riscv/portasm.S
View File

@@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2015-2024 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
@@ -186,14 +186,21 @@ rtos_save_\name\()_coproc_norestore:
/**
* @brief Restore the HWLP registers contained in the dedicated save area if the given task ever used it.
* This routine sets the HWLP context to clean in any case.
* This routine sets the HWLP context to dirty if the task ever used it and any of the loop counter
* is not zero. Else, it sets it to clean.
*
* @param a0 StaticTask address for the newly scheduled task
*/
hwlp_restore_if_used:
addi sp, sp, -16
sw ra, (sp)
/* Check if the HWLP was in use beforehand */
/* Re-enable the HWLP coprocessor */
csrwi CSR_HWLP_STATE_REG, HWLP_CLEAN_STATE
/* Check if the HWLP was ever used by this task, if yes:
* - Set HWLP state to DIRTY if any of the HWLP counter is != 0.
* Please note that the `hwlp_restore_regs` macro will set the DIRTY bit!
* - Keep the state as CLEAN if both counters are 0.
*/
li a1, 0
li a2, HWLP_COPROC_IDX
call pxPortGetCoprocArea
@@ -201,13 +208,22 @@ hwlp_restore_if_used:
lw a1, RV_COPROC_ENABLE(a0)
/* To avoid having branches below, set the coprocessor enable flag now */
andi a2, a1, 1 << HWLP_COPROC_IDX
beqz a2, _hwlp_restore_never_used
beqz a2, _hwlp_restore_end
/* Enable bit was set, restore the coprocessor context */
lw a0, RV_COPROC_SA+HWLP_COPROC_IDX*4(a0) /* a0 = RvCoprocSaveArea->sa_coprocs[HWLP_COPROC_IDX] */
/* This will set the dirty flag for sure */
hwlp_restore_regs a0
_hwlp_restore_never_used:
/* Clear the context */
#if SOC_CPU_HAS_HWLOOP_STATE_BUG && ESP32P4_REV_MIN_FULL <= 1
/* The hardware doesn't update the HWLP state properly after executing the last instruction,
* as such, we must manually put the state of the HWLP to dirty now if any counter is not 0 */
csrr a0, CSR_LOOP0_COUNT
bnez a0, _hwlp_restore_end
csrr a0, CSR_LOOP1_COUNT
bnez a0, _hwlp_restore_end
/* The counters are 0, cleaning the state */
#endif /* SOC_CPU_HAS_HWLOOP_STATE_BUG && ESP32P4_REV_MIN_FULL <= 1 */
csrwi CSR_HWLP_STATE_REG, HWLP_CLEAN_STATE
_hwlp_restore_end:
lw ra, (sp)
addi sp, sp, 16
ret
@@ -458,6 +474,11 @@ rtos_current_tcb:
.global rtos_int_enter
.type rtos_int_enter, @function
rtos_int_enter:
#if SOC_CPU_COPROC_NUM > 0
/* Use s2 to store the state of the coprocessors */
li s2, 0
#endif /* SOC_CPU_COPROC_NUM > 0 */
#if ( configNUM_CORES > 1 )
csrr s0, mhartid /* s0 = coreID */
slli s0, s0, 2 /* s0 = coreID * 4 */
@@ -483,7 +504,6 @@ rtos_int_enter:
li a0, 0 /* return 0 in case we are going to branch */
bnez a1, rtos_int_enter_end /* if (port_uxInterruptNesting[coreID] > 0) jump to rtos_int_enter_end */
li s2, 0
#if SOC_CPU_COPROC_NUM > 0
/* Disable the coprocessors to forbid the ISR from using it */
#if SOC_CPU_HAS_PIE
@@ -525,6 +545,7 @@ rtos_int_enter:
addi a1, a1, -HWLP_DIRTY_STATE
bnez a1, 1f
/* State is dirty! The hardware loop feature was used, save the registers */
ori s2, s2, 1 << HWLP_COPROC_IDX /* Mark the HWLP coprocessor as enabled (dirty) */
li a1, 1 /* Allocate the save area if not already allocated */
li a2, HWLP_COPROC_IDX
mv s1, ra
@@ -537,8 +558,6 @@ rtos_int_enter:
/* Get the area where we need to save the HWLP registers */
lw a0, RV_COPROC_SA+HWLP_COPROC_IDX*4(a0) /* a0 = RvCoprocSaveArea->sa_coprocs[\coproc_idx] */
hwlp_save_regs a0
/* Disable the HWLP feature so that ISR cannot use them */
csrwi CSR_HWLP_STATE_REG, HWLP_CLEAN_STATE
1:
#endif
@@ -559,9 +578,16 @@ rtos_int_enter:
ESP_HW_STACK_GUARD_MONITOR_START_CUR_CORE a0 a1
#endif /* CONFIG_ESP_SYSTEM_HW_STACK_GUARD */
rtos_int_enter_end:
/* Disable the HWLP coprocessor for ISRs */
#if SOC_CPU_HAS_HWLOOP
csrwi CSR_HWLP_STATE_REG, HWLP_OFF_STATE
#endif
#if SOC_CPU_COPROC_NUM > 0
/* Return the coprocessor context from s2 */
mv a0, s2
rtos_int_enter_end:
#endif /* SOC_CPU_COPROC_NUM > 0 */
ret
/**
@@ -577,8 +603,8 @@ rtos_int_enter_end:
.type rtos_int_exit, @function
rtos_int_exit:
/* To speed up this routine and because this current routine is only meant to be called from the interrupt
* handler, let's use callee-saved registers instead of stack space. Registers `s5-s11` are not used by
* the caller */
* handler, let's use callee-saved registers instead of stack space */
mv s10, ra
mv s11, a0
#if SOC_CPU_COPROC_NUM > 0
/* Save a1 as it contains the bitmap with the enabled coprocessors */
@@ -586,10 +612,10 @@ rtos_int_exit:
#endif
#if ( configNUM_CORES > 1 )
csrr a1, mhartid /* a1 = coreID */
slli a1, a1, 2 /* a1 = a1 * 4 */
csrr s7, mhartid /* s7 = coreID */
slli s7, s7, 2 /* s7 = s7 * 4 */
la a0, port_xSchedulerRunning /* a0 = &port_xSchedulerRunning */
add a0, a0, a1 /* a0 = &port_xSchedulerRunning[coreID] */
add a0, a0, s7 /* a0 = &port_xSchedulerRunning[coreID] */
lw a0, (a0) /* a0 = port_xSchedulerRunning[coreID] */
#else
lw a0, port_xSchedulerRunning /* a0 = port_xSchedulerRunning */
@@ -599,7 +625,7 @@ rtos_int_exit:
/* Update nesting interrupts counter */
la a2, port_uxInterruptNesting /* a2 = &port_uxInterruptNesting */
#if ( configNUM_CORES > 1 )
add a2, a2, a1 /* a2 = &port_uxInterruptNesting[coreID] // a1 already contains coreID * 4 */
add a2, a2, s7 /* a2 = &port_uxInterruptNesting[coreID] // s7 already contains coreID * 4 */
#endif /* ( configNUM_CORES > 1 ) */
lw a0, 0(a2) /* a0 = port_uxInterruptNesting[coreID] */
@@ -611,84 +637,66 @@ rtos_int_exit:
bnez a0, rtos_int_exit_end
isr_skip_decrement:
/* If the CPU reached this label, a2 (uxInterruptNesting) is 0 for sure */
/* Schedule the next task if a yield is pending */
la s7, xPortSwitchFlag /* s7 = &xPortSwitchFlag */
#if ( configNUM_CORES > 1 )
add s7, s7, a1 /* s7 = &xPortSwitchFlag[coreID] // a1 already contains coreID * 4 */
#endif /* ( configNUM_CORES > 1 ) */
lw a0, 0(s7) /* a0 = xPortSwitchFlag[coreID] */
beqz a0, no_switch_restore_coproc /* if (xPortSwitchFlag[coreID] == 0) jump to no_switch_restore_coproc */
/* Preserve return address and schedule next task. To speed up the process, and because this current routine
* is only meant to be called from the interrupt handle, let's save some speed and space by using callee-saved
* registers instead of stack space. Registers `s3-s11` are not used by the caller */
mv s10, ra
#if ( SOC_CPU_COPROC_NUM > 0 )
/* In the cases where the newly scheduled task is different from the previously running one,
* we have to disable the coprocessors to let them trigger an exception on first use.
* Else, if the same task is scheduled, restore the former coprocessors state (before the interrupt) */
call rtos_current_tcb
/* Keep former TCB in s9 */
mv s9, a0
#endif
call vTaskSwitchContext
#if ( SOC_CPU_COPROC_NUM == 0 )
mv ra, s10 /* Restore original return address */
#endif
/* Clears the switch pending flag (stored in s7) */
sw zero, 0(s7) /* xPortSwitchFlag[coreID] = 0; */
#if ( SOC_CPU_COPROC_NUM > 0 )
/* If the Task to schedule is NOT the same as the former one (s9), keep the coprocessors disabled */
/* Keep the current TCB in a0 */
call rtos_current_tcb
mv ra, s10 /* Restore original return address */
beq a0, s9, no_switch_restore_coproc
#if SOC_CPU_HAS_HWLOOP
/* We have to restore the context of the HWLP if the newly scheduled task used it before. In all cases, this
* routine will also clean the state and set it to clean */
mv s7, ra
/* a0 contains the current TCB address */
call hwlp_restore_if_used
mv ra, s7
#endif /* SOC_CPU_HAS_HWLOOP */
#if SOC_CPU_HAS_FPU
/* Disable the FPU in the `mstatus` value to return */
li a1, ~CSR_MSTATUS_FPU_DISABLE
and s11, s11, a1
#endif /* SOC_CPU_HAS_FPU */
j no_switch_restored
#endif /* ( SOC_CPU_COPROC_NUM > 0 ) */
no_switch_restore_coproc:
/* We reach here either because there is no switch scheduled or because the TCB that is going to be scheduled
* is the same as the one that has been interrupted. In both cases, we need to restore the coprocessors status */
/* Schedule the next task if a yield is pending */
la s6, xPortSwitchFlag /* s6 = &xPortSwitchFlag */
#if ( configNUM_CORES > 1 )
add s6, s6, s7 /* s6 = &xPortSwitchFlag[coreID] // s7 already contains coreID * 4 */
#endif /* ( configNUM_CORES > 1 ) */
lw a1, 0(s6) /* a1 = xPortSwitchFlag[coreID] */
bnez a1, context_switch_requested /* if (xPortSwitchFlag[coreID] != 0) jump to context_switch_requested */
no_context_switch:
/* No need to do anything on the FPU side, its state is already saved in `s11` */
#if SOC_CPU_HAS_HWLOOP
/* Check if the ISR altered the state of the HWLP */
csrr a1, CSR_HWLP_STATE_REG
addi a1, a1, -HWLP_DIRTY_STATE
bnez a1, 1f
/* ISR used the HWLP, restore the HWLP context! */
mv s7, ra
/* a0 contains the current TCB address */
call hwlp_restore_if_used
mv ra, s7
csrwi CSR_HWLP_STATE_REG, HWLP_CLEAN_STATE
/* If the HWLP coprocessor has a hardware bug with its state, manually set the state to DIRTY
* if it was already dirty before the interrupt, else, keep it to CLEAN */
#if SOC_CPU_HAS_HWLOOP_STATE_BUG && ESP32P4_REV_MIN_FULL <= 1
andi a1, s8, 1 << HWLP_COPROC_IDX
beqz a1, 1f
/* To re-enable the HWLP coprocessor, set the status to DIRTY */
csrwi CSR_HWLP_STATE_REG, HWLP_DIRTY_STATE
1:
/* Else, the ISR hasn't touched HWLP registers, we don't need to restore the HWLP registers */
#endif /* SOC_CPU_HAS_HWLOOP_STATE_BUG && ESP32P4_REV_MIN_FULL <= 1 */
#endif /* SOC_CPU_HAS_HWLOOP */
#if SOC_CPU_HAS_PIE
andi a0, s8, 1 << PIE_COPROC_IDX
beqz a0, 2f
pie_enable a0
2:
/* Re-enable the PIE coprocessor if it was used */
andi a1, s8, 1 << PIE_COPROC_IDX
beqz a1, 1f
pie_enable a1
1:
#endif /* SOC_CPU_HAS_PIE */
j restore_stack_pointer
no_switch_restored:
context_switch_requested:
#if ( SOC_CPU_COPROC_NUM > 0 )
/* Preserve former TCB in s9 */
mv s9, a0
#endif /* ( SOC_CPU_COPROC_NUM > 0 ) */
call vTaskSwitchContext
/* Clears the switch pending flag (stored in s6) */
sw zero, 0(s6) /* xPortSwitchFlag[coreID] = 0; */
#if ( SOC_CPU_COPROC_NUM > 0 )
/* If the Task to schedule is NOT the same as the former one (s9), keep the coprocessors disabled. */
/* Check if the new TCB is the same as the previous one */
call rtos_current_tcb
beq a0, s9, no_context_switch
#endif /* ( SOC_CPU_COPROC_NUM > 0 ) */
#if SOC_CPU_HAS_HWLOOP
call hwlp_restore_if_used
#endif /* SOC_CPU_HAS_HWLOOP */
restore_stack_pointer:
#if CONFIG_ESP_SYSTEM_HW_STACK_GUARD
/* esp_hw_stack_guard_monitor_stop(); pass the scratch registers */
@@ -698,10 +706,8 @@ no_switch_restored:
#if ( configNUM_CORES > 1 )
/* Recover the stack of next task and prepare to exit */
csrr a1, mhartid
slli a1, a1, 2
la a0, pxCurrentTCBs /* a0 = &pxCurrentTCBs */
add a0, a0, a1 /* a0 = &pxCurrentTCBs[coreID] */
add a0, a0, s7 /* a0 = &pxCurrentTCBs[coreID] */
lw a0, 0(a0) /* a0 = pxCurrentTCBs[coreID] */
lw sp, 0(a0) /* sp = previous sp */
#else
@@ -724,4 +730,5 @@ no_switch_restored:
rtos_int_exit_end:
mv a0, s11 /* a0 = new mstatus */
mv ra, s10
ret

12
components/riscv/vectors.S
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@@ -1,5 +1,5 @@
/*
* SPDX-FileCopyrightText: 2017-2024 Espressif Systems (Shanghai) CO LTD
* SPDX-FileCopyrightText: 2017-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
@@ -236,6 +236,16 @@ _panic_handler:
la ra, _return_from_exception
/* EXT_ILL CSR should contain the reason for the Illegal Instruction */
csrrw a0, EXT_ILL_CSR, zero
#if SOC_CPU_HAS_HWLOOP
/* Check if the HWLP bit is set. */
andi a1, a0, EXT_ILL_RSN_HWLP
beqz a1, hwlp_not_used
/* HWLP used in an ISR, abort */
mv a0, sp
j vPortCoprocUsedInISR
hwlp_not_used:
#endif /* SOC_CPU_HAS_HWLOOP */
/* Hardware loop cannot be treated lazily, so we should never end here if a HWLP instruction is used */
#if SOC_CPU_HAS_PIE
/* Check if the PIE bit is set. */

4
components/soc/esp32p4/include/soc/Kconfig.soc_caps.in
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@@ -523,6 +523,10 @@ config SOC_CPU_HAS_HWLOOP
bool
default y
config SOC_CPU_HAS_HWLOOP_STATE_BUG
bool
default y
config SOC_CPU_HAS_PIE
bool
default y

1
components/soc/esp32p4/include/soc/soc_caps.h
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@@ -179,6 +179,7 @@
#define SOC_CPU_HAS_FPU 1
#define SOC_CPU_HAS_FPU_EXT_ILL_BUG 1 // EXT_ILL CSR doesn't support FLW/FSW
#define SOC_CPU_HAS_HWLOOP 1
#define SOC_CPU_HAS_HWLOOP_STATE_BUG 1 // HWLOOP state doesn't go to DIRTY after executing the last instruction of a loop
/* PIE coprocessor assembly is only supported with GCC compiler */
#define SOC_CPU_HAS_PIE 1