| /* Copyright (c) 2012 The Chromium OS Authors. All rights reserved. |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| * |
| * Context swtching |
| */ |
| |
| #include "config.h" |
| |
| .text |
| |
| .syntax unified |
| .code 16 |
| |
| /** |
| * Task context switching |
| * |
| * Change the task scheduled after returning from the exception. |
| * |
| * Save the registers of the current task below the exception context on |
| * its task, then restore the live registers of the next task and set the |
| * process stack pointer to the new stack. |
| * |
| * r0: pointer to the task to switch from |
| * r1: pointer to the task to switch to |
| * |
| * must be called from interrupt context |
| * |
| * the structure of the saved context on the stack is : |
| * r0, r1, r2, r3, r12, lr, pc, psr, r4, r5, r6, r7, r8, r9, r10, r11 |
| * exception frame <|> additional registers |
| */ |
| .global __switchto |
| .thumb_func |
| __switchto: |
| mrs r3, psp @ get the task stack where the context has been saved |
| ldr r2, [r1] @ get the new scheduled task stack pointer |
| stmdb r3!, {r4-r11} @ save additional r4-r11 in the task stack |
| ldmia r2!, {r4-r11} @ restore r4-r11 for the next task context |
| str r3, [r0] @ save the task stack pointer in its context |
| msr psp, r2 @ set the process stack pointer to exception context |
| bx lr @ return from exception |
| |
| /** |
| * Start the task scheduling. r0 is a pointer to task_stack_ready, which is |
| * set to 1 after the task stack is set up. |
| */ |
| .global __task_start |
| .thumb_func |
| __task_start: |
| ldr r2,=scratchpad @ area used as dummy thread stack for the first switch |
| #ifdef CONFIG_FPU |
| mov r3, #6 @ use : priv. mode / thread stack / floating point on |
| #else |
| mov r3, #2 @ use : priv. mode / thread stack / no floating point |
| #endif |
| add r2, #17*4 @ put the pointer at the top of the stack |
| mov r1, #0 @ __Schedule parameter : re-schedule nothing |
| msr psp, r2 @ setup a thread stack up to the first context switch |
| mov r2, #1 |
| isb @ ensure the write is done |
| msr control, r3 |
| mov r3, r0 |
| mov r0, #0 @ __Schedule parameter : de-schedule nothing |
| isb @ ensure the write is done |
| str r2, [r3] @ Task scheduling is now active |
| bl __schedule @ execute the task with the highest priority |
| /* we should never return here */ |
| mov r0, #1 @ set to EC_ERROR_UNKNOWN |
| bx lr |
| |
