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Add comments and tiny improvements to STM32 flash loader algorithm 

Add comments to assembly flash loader for STM32. Add tiny improvement in
size of the algorithm (40 vs 48 bytes) and tiny speed improvement (~1.5%,
as time is wasted on waiting for end of operation anyway).

Signed-off-by: Freddie Chopin <freddie_chopin@op.pl>
This commit is contained in:
Freddie Chopin 2010-11-13 15:42:00 +01:00 committed by Øyvind Harboe
parent 6287c23b32
commit 015bf55944
2 changed files with 42 additions and 37 deletions
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46
contrib/loaders/flash/stm32x.s
View File

@ -19,7 +19,10 @@
***************************************************************************/
.text
.arm
.syntax unified
.thumb
.thumb_func
.global write
/*
r0 - source address
@ -27,26 +30,27 @@
r2 - count (halfword-16bit)
r3 - result
r4 - temp
r5 - temp
*/
write:
ldr r4, STM32_FLASH_CR
ldr r5, STM32_FLASH_SR
mov r3, #1
str r3, [r4, #0]
ldrh r3, [r0], #2
strh r3, [r1], #2
busy:
ldr r3, [r5, #0]
tst r3, #0x01
beq busy
tst r3, #0x14
bne exit
subs r2, r2, #1
bne write
exit:
bkpt #0
#define STM32_FLASH_CR_OFFSET 0x10 /* offset of CR register in FLASH struct */
#define STM32_FLASH_SR_OFFSET 0x0c /* offset of CR register in FLASH struct */
STM32_FLASH_CR: .word 0x40022010
STM32_FLASH_SR: .word 0x4002200C
write:
ldr r4, STM32_FLASH_BASE
write_half_word:
movs r3, #0x01
str r3, [r4, #STM32_FLASH_CR_OFFSET] /* PG (bit0) == 1 => flash programming enabled */
ldrh r3, [r0], #0x02 /* read one half-word from src, increment ptr */
strh r3, [r1], #0x02 /* write one half-word from src, increment ptr */
busy:
ldr r3, [r4, #STM32_FLASH_SR_OFFSET]
tst r3, #0x01 /* BSY (bit0) == 1 => operation in progress */
beq busy /* wait more... */
tst r3, #0x14 /* PGERR (bit2) == 1 or WRPRTERR (bit4) == 1 => error */
bne exit /* fail... */
subs r2, r2, #0x01 /* decrement counter */
bne write_half_word /* write next half-word if anything left */
exit:
bkpt #0x00
STM32_FLASH_BASE: .word 0x40022000 /* base address of FLASH struct */

33
src/flash/nor/stm32x.c
View File

@ -503,25 +503,26 @@ static int stm32x_write_block(struct flash_bank *bank, uint8_t *buffer,
/* see contib/loaders/flash/stm32x.s for src */
static const uint8_t stm32x_flash_write_code[] = {
/* #define STM32_FLASH_CR_OFFSET 0x10 */
/* #define STM32_FLASH_SR_OFFSET 0x0C */
/* write: */
0xDF, 0xF8, 0x24, 0x40, /* ldr r4, STM32_FLASH_CR */
0x09, 0x4D, /* ldr r5, STM32_FLASH_SR */
0x4F, 0xF0, 0x01, 0x03, /* mov r3, #1 */
0x23, 0x60, /* str r3, [r4, #0] */
0x30, 0xF8, 0x02, 0x3B, /* ldrh r3, [r0], #2 */
0x21, 0xF8, 0x02, 0x3B, /* strh r3, [r1], #2 */
0xdf, 0xf8, 0x20, 0x40, /* ldr r4, STM32_FLASH_BASE */
/* write_half_word: */
0x01, 0x23, /* movs r3, #0x01 */
0x23, 0x61, /* str r3, [r4, #STM32_FLASH_CR_OFFSET] */
0x30, 0xf8, 0x02, 0x3b, /* ldrh r3, [r0], #0x02 */
0x21, 0xf8, 0x02, 0x3b, /* strh r3, [r1], #0x02 */
/* busy: */
0x2B, 0x68, /* ldr r3, [r5, #0] */
0x13, 0xF0, 0x01, 0x0F, /* tst r3, #0x01 */
0xFB, 0xD0, /* beq busy */
0x13, 0xF0, 0x14, 0x0F, /* tst r3, #0x14 */
0x01, 0xD1, /* bne exit */
0x01, 0x3A, /* subs r2, r2, #1 */
0xED, 0xD1, /* bne write */
0xe3, 0x68, /* ldr r3, [r4, #STM32_FLASH_SR_OFFSET] */
0x13, 0xf0, 0x01, 0x0f, /* tst r3, #0x01 */
0xfb, 0xd0, /* beq busy */
0x13, 0xf0, 0x14, 0x0f, /* tst r3, #0x14 */
0x01, 0xd1, /* bne exit */
0x01, 0x3a, /* subs r2, r2, #0x01 */
0xf0, 0xd1, /* bne write_half_word */
/* exit: */
0x00, 0xBE, /* bkpt #0 */
0x10, 0x20, 0x02, 0x40, /* STM32_FLASH_CR: .word 0x40022010 */
0x0C, 0x20, 0x02, 0x40 /* STM32_FLASH_SR: .word 0x4002200C */
0x00, 0xbe, /* bkpt #0x00 */
0x00, 0x20, 0x02, 0x40, /* STM32_FLASH_BASE: .word 0x40022000 */
};
/* flash write code */