esp-idf/components/freertos/port/riscv/portasm.S

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// Copyright 2015-2020 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
.global uxInterruptNesting
.global uxSchedulerRunning
.global xIsrStackTop
.global pxCurrentTCB
.global vTaskSwitchContext
.global xPortSwitchFlag
.section .text
/**
* This function makes the RTOS aware about a ISR entering, it takes the
* current task stack saved, places into the TCB, loads the ISR stack
* the interrupted stack must be passed in a0. It needs to receive the
* ISR nesting code improvements
*/
.global rtos_int_enter
.type rtos_int_enter, @function
rtos_int_enter:
/* preserve the return address */
mv t1, ra
mv t2, a0
/* scheduler not enabled, jump directly to ISR handler */
lw t0, uxSchedulerRunning
beq t0,zero, rtos_enter_end
/* increments the ISR nesting count */
la t3, uxInterruptNesting
lw t4, 0x0(t3)
addi t5,t4,1
sw t5, 0x0(t3)
/* If reached here from another low-prio ISR, skip stack pushing to TCB */
bne t4,zero, rtos_enter_end
/* Save current TCB and load the ISR stack */
lw t0, pxCurrentTCB
sw t2, 0x0(t0)
lw sp, xIsrStackTop
rtos_enter_end:
mv ra, t1
ret
/**
* Recovers the next task to run stack pointer and place it into
* a0, then the interrupt handler can restore the context of
* the next task
*/
.global rtos_int_exit
.type rtos_int_exit, @function
rtos_int_exit:
/* may skip RTOS aware interrupt since scheduler was not started */
lw t0, uxSchedulerRunning
beq t0,zero, rtos_exit_end
/* update nesting interrupts counter */
la t2, uxInterruptNesting
lw t3, 0x0(t2)
/* Already zero, protect against underflow */
beq t3, zero, isr_skip_decrement
addi t3,t3, -1
sw t3, 0x0(t2)
isr_skip_decrement:
/* may still have interrupts pending, skip section below and exit */
bne t3,zero,rtos_exit_end
/* Schedule the next task if a yield is pending */
la t0, xPortSwitchFlag
lw t2, 0x0(t0)
beq t2, zero, no_switch
/* preserve return address and schedule next task
stack pointer for riscv should always be 16 byte aligned */
addi sp,sp,-16
sw ra, 0(sp)
call vTaskSwitchContext
lw ra, 0(sp)
addi sp, sp, 16
/* Clears the switch pending flag */
la t0, xPortSwitchFlag
mv t2, zero
sw t2, 0x0(t0)
no_switch:
/* Recover the stack of next task and prepare to exit : */
lw a0, pxCurrentTCB
lw a0, 0x0(a0)
rtos_exit_end:
ret