len0rd/rockbox
1
0
Fork 1
mirror of https://github.com/Rockbox/rockbox.git synced 2025-10-13 18:17:39 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

arm: add ARMv7-M support for thread context switching

Browse source 
On ARMv7-M, stm/ldm instructions can't include SP, so we must
load and store that separately. This changes the order of
registers in the context struct, but it doesn't seem to be
accessed anywhere else so this shouldn't cause any problems.

Change-Id: Ie1cd23272f23384e030f51f0b76739624fa7332b
This commit is contained in:
Aidan MacDonald 2024-11-14 15:06:07 +00:00 • committed by Solomon Peachy
parent 6712779ccb
commit 1c96d51717
2 changed files with 26 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

11
firmware/asm/arm/thread.c
View file

@ -61,7 +61,12 @@ static void __attribute__((naked)) USED_ATTR start_thread(void)
static inline void store_context(void* addr)
{
asm volatile(
#if defined(CPU_ARM_MICRO) && ARCH_VERSION >= 7
"stmia %0, { r4-r11, lr } \n"
"str sp, [%0, #36] \n"
#else
"stmia %0, { r4-r11, sp, lr } \n"
#endif
: : "r" (addr)
);
}
@ -85,7 +90,13 @@ static inline void load_context(const void* addr)
"ldmiane %0, { r0, pc } \n"
#endif
#if defined(CPU_ARM_MICRO) && ARCH_VERSION >= 7
"mov r0, %0 \n"
"ldmia r0, { r4-r11, lr } \n"
"ldr sp, [r0, #36] \n"
#else
"ldmia %0, { r4-r11, sp, lr } \n" /* Load regs r4 to r14 from context */
#endif
END_ARM_ASM_SYNTAX_UNIFIED
: : "r" (addr) : "r0" /* only! */
);

15
firmware/asm/arm/thread.h
View file

@ -21,6 +21,20 @@
#include "config.h"
#if defined(CPU_ARM_MICRO) && ARCH_VERSION >= 7
/*
* Cortex-M cannot load/store SP with ldm/stm so we need to store it
* separately. This makes it slightly more efficient to store SP last
* so as not to split the register list.
*/
struct regs
{
uint32_t r[8]; /* 0-28 - Registers r4-r11 */
uint32_t lr; /* 32 - r14 (lr) */
uint32_t sp; /* 36 - Stack pointer (r13) */
uint32_t start; /* 40 - Thread start address, or NULL when started */
};
#else
struct regs
{
uint32_t r[8]; /* 0-28 - Registers r4-r11 */
@ -28,6 +42,7 @@ struct regs
uint32_t lr; /* 36 - r14 (lr) */
uint32_t start; /* 40 - Thread start address, or NULL when started */
};
#endif
#if (CONFIG_PLATFORM & PLATFORM_HOSTED)
#include <errno.h>