2 * FreeRTOS Kernel V10.0.1
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3 * Copyright (C) 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software.
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 * http://www.FreeRTOS.org
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23 * http://aws.amazon.com/freertos
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25 * 1 tab == 4 spaces!
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28 #include "FreeRTOSConfig.h"
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30 #define portCONTEXT_SIZE 132
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31 #define portEPC_STACK_LOCATION 124
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32 #define portSTATUS_STACK_LOCATION 128
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34 #ifdef __LANGUAGE_ASSEMBLY__
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36 /******************************************************************/
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37 .macro portSAVE_CONTEXT
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39 /* Make room for the context. First save the current status so it can be
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40 manipulated, and the cause and EPC registers so their original values are
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43 addiu sp, sp, -portCONTEXT_SIZE
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44 mfc0 k1, _CP0_STATUS
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46 /* Also save s6 and s5 so they can be used. Any nesting interrupts should
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47 maintain the values of these registers across the ISR. */
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50 sw k1, portSTATUS_STACK_LOCATION(sp)
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52 /* Prepare to enable interrupts above the current priority.
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53 k0 = k0 >> 10. Moves RIPL[17:10] to [7:0] */
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56 /* Insert bit field. 7 bits k0[6:0] to k1[16:10] */
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59 /* Sets CP0.Status.IPL = CP0.Cause.RIPL
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60 Copy the MSB of the IPL, but it would be an error if it was set anyway. */
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63 /* MSB of IPL is bit[18] of CP0.Status */
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66 /* CP0.Status[5:1] = 0 b[5]=Rsvd, b[4]=UM,
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67 b[3]=Rsvd, b[2]=ERL, b[1]=EXL
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68 Setting EXL=0 allows higher priority interrupts
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69 to preempt this handler */
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73 /* s5 is used as the frame pointer. */
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76 /* Check the nesting count value. */
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77 la k0, uxInterruptNesting
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80 /* If the nesting count is 0 then swap to the the system stack, otherwise
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81 the system stack is already being used. */
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85 /* Swap to the system stack. */
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89 /* Increment and save the nesting count. */
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93 /* s6 holds the EPC value, this is saved after interrupts are re-enabled. */
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96 /* Re-enable interrupts. */
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97 mtc0 k1, _CP0_STATUS
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99 /* Save the context into the space just created. s6 is saved again
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100 here as it now contains the EPC value. No other s registers need be
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102 sw ra, 120(s5) /* Return address (RA=R31) */
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103 sw s8, 116(s5) /* Frame Pointer (FP=R30) */
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120 sw s6, portEPC_STACK_LOCATION(s5)
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123 /* MEC14xx does not have DSP, removed 7 words */
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129 /* Update the task stack pointer value if nesting is zero. */
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130 la s6, uxInterruptNesting
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136 /* Save the stack pointer. */
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137 la s6, uxSavedTaskStackPointer
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142 /******************************************************************/
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143 .macro portRESTORE_CONTEXT
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145 /* Restore the stack pointer from the TCB. This is only done if the
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146 nesting count is 1. */
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147 la s6, uxInterruptNesting
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152 la s6, uxSavedTaskStackPointer
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155 /* Restore the context.
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156 MCHP MEC14xx does not include DSP */
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164 /* s6 is loaded as it was used as a scratch register and therefore saved
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165 as part of the interrupt context. */
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186 /* Protect access to the k registers, and others. */
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190 /* Decrement the nesting count. */
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191 la k0, uxInterruptNesting
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196 lw k0, portSTATUS_STACK_LOCATION(s5)
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197 lw k1, portEPC_STACK_LOCATION(s5)
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199 /* Leave the stack in its original state. First load sp from s5, then
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200 restore s5 from the stack. */
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203 addiu sp, sp, portCONTEXT_SIZE
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205 mtc0 k0, _CP0_STATUS
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213 #endif /* #ifdef __LANGUAGE_ASSEMBLY__ */
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