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215 lines
6.1 KiB
C
215 lines
6.1 KiB
C
/*
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* FreeRTOS Kernel <DEVELOPMENT BRANCH>
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* Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* SPDX-License-Identifier: MIT
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* https://www.FreeRTOS.org
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* https://github.com/FreeRTOS
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*
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*/
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#include "FreeRTOSConfig.h"
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#define portCONTEXT_SIZE 132
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#define portEPC_STACK_LOCATION 124
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#define portSTATUS_STACK_LOCATION 128
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#ifdef __LANGUAGE_ASSEMBLY__
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/******************************************************************/
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.macro portSAVE_CONTEXT
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/* Make room for the context. First save the current status so it can be
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manipulated, and the cause and EPC registers so their original values are
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captured. */
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mfc0 k0, _CP0_CAUSE
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addiu sp, sp, -portCONTEXT_SIZE
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mfc0 k1, _CP0_STATUS
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/* Also save s6 and s5 so they can be used. Any nesting interrupts should
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maintain the values of these registers across the ISR. */
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sw s6, 44(sp)
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sw s5, 40(sp)
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sw k1, portSTATUS_STACK_LOCATION(sp)
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/* Prepare to enable interrupts above the current priority.
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k0 = k0 >> 10. Moves RIPL[17:10] to [7:0] */
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srl k0, k0, 0xa
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/* Insert bit field. 7 bits k0[6:0] to k1[16:10] */
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ins k1, k0, 10, 7
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/* Sets CP0.Status.IPL = CP0.Cause.RIPL
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Copy the MSB of the IPL, but it would be an error if it was set anyway. */
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srl k0, k0, 0x7
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/* MSB of IPL is bit[18] of CP0.Status */
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ins k1, k0, 18, 1
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/* CP0.Status[5:1] = 0 b[5]=Rsvd, b[4]=UM,
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b[3]=Rsvd, b[2]=ERL, b[1]=EXL
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Setting EXL=0 allows higher priority interrupts
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to preempt this handler */
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ins k1, zero, 1, 4
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/* s5 is used as the frame pointer. */
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add s5, zero, sp
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/* Check the nesting count value. */
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la k0, uxInterruptNesting
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lw s6, (k0)
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/* If the nesting count is 0 then swap to the the system stack, otherwise
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the system stack is already being used. */
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bne s6, zero, 1f
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nop
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/* Swap to the system stack. */
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la sp, xISRStackTop
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lw sp, (sp)
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/* Increment and save the nesting count. */
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1: addiu s6, s6, 1
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sw s6, 0(k0)
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/* s6 holds the EPC value, this is saved after interrupts are re-enabled. */
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mfc0 s6, _CP0_EPC
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/* Re-enable interrupts. */
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mtc0 k1, _CP0_STATUS
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/* Save the context into the space just created. s6 is saved again
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here as it now contains the EPC value. No other s registers need be
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saved. */
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sw ra, 120(s5) /* Return address (RA=R31) */
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sw s8, 116(s5) /* Frame Pointer (FP=R30) */
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sw t9, 112(s5)
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sw t8, 108(s5)
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sw t7, 104(s5)
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sw t6, 100(s5)
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sw t5, 96(s5)
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sw t4, 92(s5)
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sw t3, 88(s5)
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sw t2, 84(s5)
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sw t1, 80(s5)
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sw t0, 76(s5)
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sw a3, 72(s5)
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sw a2, 68(s5)
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sw a1, 64(s5)
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sw a0, 60(s5)
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sw v1, 56(s5)
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sw v0, 52(s5)
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sw s6, portEPC_STACK_LOCATION(s5)
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sw $1, 16(s5)
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/* MEC14xx does not have DSP, removed 7 words */
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mfhi s6
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sw s6, 12(s5)
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mflo s6
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sw s6, 8(s5)
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/* Update the task stack pointer value if nesting is zero. */
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la s6, uxInterruptNesting
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lw s6, (s6)
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addiu s6, s6, -1
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bne s6, zero, 1f
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nop
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/* Save the stack pointer. */
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la s6, uxSavedTaskStackPointer
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sw s5, (s6)
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1:
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.endm
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/******************************************************************/
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.macro portRESTORE_CONTEXT
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/* Restore the stack pointer from the TCB. This is only done if the
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nesting count is 1. */
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la s6, uxInterruptNesting
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lw s6, (s6)
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addiu s6, s6, -1
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bne s6, zero, 1f
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nop
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la s6, uxSavedTaskStackPointer
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lw s5, (s6)
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/* Restore the context.
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MCHP MEC14xx does not include DSP */
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1:
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lw s6, 8(s5)
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mtlo s6
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lw s6, 12(s5)
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mthi s6
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lw $1, 16(s5)
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/* s6 is loaded as it was used as a scratch register and therefore saved
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as part of the interrupt context. */
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lw s6, 44(s5)
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lw v0, 52(s5)
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lw v1, 56(s5)
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lw a0, 60(s5)
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lw a1, 64(s5)
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lw a2, 68(s5)
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lw a3, 72(s5)
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lw t0, 76(s5)
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lw t1, 80(s5)
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lw t2, 84(s5)
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lw t3, 88(s5)
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lw t4, 92(s5)
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lw t5, 96(s5)
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lw t6, 100(s5)
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lw t7, 104(s5)
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lw t8, 108(s5)
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lw t9, 112(s5)
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lw s8, 116(s5)
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lw ra, 120(s5)
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/* Protect access to the k registers, and others. */
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di
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ehb
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/* Decrement the nesting count. */
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la k0, uxInterruptNesting
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lw k1, (k0)
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addiu k1, k1, -1
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sw k1, 0(k0)
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lw k0, portSTATUS_STACK_LOCATION(s5)
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lw k1, portEPC_STACK_LOCATION(s5)
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/* Leave the stack in its original state. First load sp from s5, then
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restore s5 from the stack. */
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add sp, zero, s5
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lw s5, 40(sp)
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addiu sp, sp, portCONTEXT_SIZE
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mtc0 k0, _CP0_STATUS
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mtc0 k1, _CP0_EPC
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ehb
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eret
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nop
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.endm
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#endif /* #ifdef __LANGUAGE_ASSEMBLY__ */
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