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d3843a5afb
Signed-off-by: Randall Spangler <rspangler@chromium.org> BUG=chrome-os-partner:8350 TEST=manual Hack a task function to return. Then see that it prints an error to the debug console and the EC continues running, instead of seeing a hard-fault. Change-Id: Iacd2b83c4d4845bb8e6c61e07c3150df8edc7e49
64 lines
2.2 KiB
ArmAsm
64 lines
2.2 KiB
ArmAsm
/* Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*
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* Context swtching
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*/
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#include "config.h"
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.text
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.syntax unified
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.code 16
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/**
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* Task context switching
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*
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* Change the task scheduled after returning from the exception.
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*
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* Save the registers of the current task below the exception context on
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* its task, then restore the live registers of the next task and set the
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* process stack pointer to the new stack.
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*
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* r0: pointer to the task to switch from
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* r1: pointer to the task to switch to
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*
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* must be called from interrupt context
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*
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* the structure of the saved context on the stack is :
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* r0, r1, r2, r3, r12, lr, pc, psr, r4, r5, r6, r7, r8, r9, r10, r11
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* exception frame <|> additional registers
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*/
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.global __switchto
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.thumb_func
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__switchto:
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mrs r3, psp @ get the task stack where the context has been saved
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ldr r2, [r1] @ get the new scheduled task stack pointer
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stmdb r3!, {r4-r11} @ save additional r4-r7 in the task stack
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ldmia r2!, {r4-r11} @ restore r4-r7 for the next task context
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str r3, [r0] @ save the task stack pointer in its context
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msr psp, r2 @ set the process stack pointer to exception context
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bx lr @ return from exception
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/**
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* Start the task scheduling
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*/
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.global task_start
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.thumb_func
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task_start:
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ldr r2,=scratchpad @ area used as dummy thread stack for the first switch
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mov r3, #2
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mov r0, #0 @ __Schedule parameter : de-schedule nothing
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mov r1, #0 @ __Schedule parameter : re-schedule nothing
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add r2, #17*4 @ put the pointer at the top of the stack
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msr psp, r2 @ setup a thread stack up to the first context switch
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isb @ ensure the write is done
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msr control, r3 @ use : priv. mode / thread stack / no floating point
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isb @ ensure the write is done
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bl __schedule @ execute the task with the highest priority
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/* we should never return here */
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mov r0, #1 @ set to EC_ERROR_UNKNOWN
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bx lr
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