[PATCH u-boot-marvell] tools: kwboot: Do not send magic seq when changing baudrate back to 115200
Marek Behún
kabel at kernel.org
Mon Nov 1 14:00:02 CET 2021
From: Pali Rohár <pali at kernel.org>
After successful transfer of whole image only two things can happen:
- BootROM starts execution of data block, which changes UART baudrate
back to 115200 Bd,
- board crashes and causes CPU reset
In both cases UART baudrate is reset to the default speed. So there is
no need to send special magic sequence to inform kwboot that baudrate is
going to be reset and kwboot does not need to wait for this event and
can do it immediately after BootROM acknowledges end of xmodem transfer.
Move ARM code for sending magic sequence from main baudrate change
section to binhdr_pre section which is executed only before changing
baudrate from the default value of 115200 Bd to some new value. Remove
kwboot code waiting for magic sequence after successful xmodem transfer.
Rationale: sometimes when using very high UART speeds, magic sequence is
damaged and kwboot fails at this last stage. Removal of this magic
sequence makes booting more stable.
Data transfer protocol (xmodem) is using checksums and retransmit, so it
already deals with possible errors on transfer line.
Signed-off-by: Pali Rohár <pali at kernel.org>
Signed-off-by: Marek Behún <marek.behun at nic.cz>
---
tools/kwboot.c | 115 ++++++++++++++++++++++++++-----------------------
1 file changed, 60 insertions(+), 55 deletions(-)
diff --git a/tools/kwboot.c b/tools/kwboot.c
index 359b43c0d8..bacca15301 100644
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -81,23 +81,15 @@ struct kwboot_block {
/* ARM code to change baudrate */
static unsigned char kwboot_baud_code[] = {
/* ; #define UART_BASE 0xd0012000 */
- /* ; #define THR 0x00 */
/* ; #define DLL 0x00 */
/* ; #define DLH 0x04 */
/* ; #define LCR 0x0c */
/* ; #define DLAB 0x80 */
/* ; #define LSR 0x14 */
- /* ; #define THRE 0x20 */
/* ; #define TEMT 0x40 */
/* ; #define DIV_ROUND(a, b) ((a + b/2) / b) */
/* ; */
/* ; u32 set_baudrate(u32 old_b, u32 new_b) { */
- /* ; const u8 *str = "$baudratechange"; */
- /* ; u8 c; */
- /* ; do { */
- /* ; c = *str++; */
- /* ; writel(UART_BASE + THR, c); */
- /* ; } while (c); */
/* ; while */
/* ; (!(readl(UART_BASE + LSR) & TEMT)); */
/* ; u32 lcr = readl(UART_BASE + LCR); */
@@ -120,29 +112,6 @@ static unsigned char kwboot_baud_code[] = {
0x0d, 0x02, 0xa0, 0xe3, /* mov r0, #0xd0000000 */
0x12, 0x0a, 0x80, 0xe3, /* orr r0, r0, #0x12000 */
- /* ; r2 = address of preamble string */
- 0xc8, 0x20, 0x8f, 0xe2, /* adr r2, preamble */
-
- /* ; Send preamble string over UART */
- /* .Lloop_preamble: */
- /* */
- /* ; Wait until Transmitter Holding is Empty */
- /* .Lloop_thre: */
- /* ; r1 = UART_BASE[LSR] & THRE */
- 0x14, 0x10, 0x90, 0xe5, /* ldr r1, [r0, #0x14] */
- 0x20, 0x00, 0x11, 0xe3, /* tst r1, #0x20 */
- 0xfc, 0xff, 0xff, 0x0a, /* beq .Lloop_thre */
-
- /* ; Put character into Transmitter FIFO */
- /* ; r1 = *r2++ */
- 0x01, 0x10, 0xd2, 0xe4, /* ldrb r1, [r2], #1 */
- /* ; UART_BASE[THR] = r1 */
- 0x00, 0x10, 0x80, 0xe5, /* str r1, [r0, #0x0] */
-
- /* ; Loop until end of preamble string */
- 0x00, 0x00, 0x51, 0xe3, /* cmp r1, #0 */
- 0xf8, 0xff, 0xff, 0x1a, /* bne .Lloop_preamble */
-
/* ; Wait until Transmitter FIFO is Empty */
/* .Lloop_txempty: */
/* ; r1 = UART_BASE[LSR] & TEMT */
@@ -168,7 +137,7 @@ static unsigned char kwboot_baud_code[] = {
/* ; Read old baudrate value */
/* ; r2 = old_baudrate */
- 0x84, 0x20, 0x9f, 0xe5, /* ldr r2, old_baudrate */
+ 0x74, 0x20, 0x9f, 0xe5, /* ldr r2, old_baudrate */
/* ; Calculate base clock */
/* ; r1 = r2 * r1 */
@@ -176,7 +145,7 @@ static unsigned char kwboot_baud_code[] = {
/* ; Read new baudrate value */
/* ; r2 = new_baudrate */
- 0x80, 0x20, 0x9f, 0xe5, /* ldr r2, new_baudrate */
+ 0x70, 0x20, 0x9f, 0xe5, /* ldr r2, new_baudrate */
/* ; Calculate new Divisor Latch */
/* ; r1 = DIV_ROUND(r1, r2) = */
@@ -225,14 +194,8 @@ static unsigned char kwboot_baud_code[] = {
0x00, 0x00, 0x51, 0xe3, /* cmp r1, #0 */
0xfc, 0xff, 0xff, 0x1a, /* bne .Lloop_sleep */
- 0x05, 0x00, 0x00, 0xea, /* b end */
-
- /* ; Preamble string */
- /* preamble: */
- 0x24, 0x62, 0x61, 0x75, /* .asciz "$baudratechange" */
- 0x64, 0x72, 0x61, 0x74,
- 0x65, 0x63, 0x68, 0x61,
- 0x6e, 0x67, 0x65, 0x00,
+ /* ; Jump to the end of execution */
+ 0x01, 0x00, 0x00, 0xea, /* b end */
/* ; Placeholder for old baudrate value */
/* old_baudrate: */
@@ -245,12 +208,66 @@ static unsigned char kwboot_baud_code[] = {
/* end: */
};
-/* ARM code for storing registers for future returning back to the bootrom */
+/* ARM code from binary header executed by BootROM before changing baudrate */
static unsigned char kwboot_baud_code_binhdr_pre[] = {
+ /* ; #define UART_BASE 0xd0012000 */
+ /* ; #define THR 0x00 */
+ /* ; #define LSR 0x14 */
+ /* ; #define THRE 0x20 */
+ /* ; */
+ /* ; void send_preamble(void) { */
+ /* ; const u8 *str = "$baudratechange"; */
+ /* ; u8 c; */
+ /* ; do { */
+ /* ; while */
+ /* ; ((readl(UART_BASE + LSR) & THRE)); */
+ /* ; c = *str++; */
+ /* ; writel(UART_BASE + THR, c); */
+ /* ; } while (c); */
+ /* ; } */
+
+ /* ; Preserve registers for BootROM */
0xfe, 0x5f, 0x2d, 0xe9, /* push { r1 - r12, lr } */
+
+ /* ; r0 = UART_BASE */
+ 0x0d, 0x02, 0xa0, 0xe3, /* mov r0, #0xd0000000 */
+ 0x12, 0x0a, 0x80, 0xe3, /* orr r0, r0, #0x12000 */
+
+ /* ; r2 = address of preamble string */
+ 0x00, 0x20, 0x8f, 0xe2, /* adr r2, .Lstr_preamble */
+
+ /* ; Skip preamble data section */
+ 0x03, 0x00, 0x00, 0xea, /* b .Lloop_preamble */
+
+ /* ; Preamble string */
+ /* .Lstr_preamble: */
+ 0x24, 0x62, 0x61, 0x75, /* .asciz "$baudratechange" */
+ 0x64, 0x72, 0x61, 0x74,
+ 0x65, 0x63, 0x68, 0x61,
+ 0x6e, 0x67, 0x65, 0x00,
+
+ /* ; Send preamble string over UART */
+ /* .Lloop_preamble: */
+ /* */
+ /* ; Wait until Transmitter Holding is Empty */
+ /* .Lloop_thre: */
+ /* ; r1 = UART_BASE[LSR] & THRE */
+ 0x14, 0x10, 0x90, 0xe5, /* ldr r1, [r0, #0x14] */
+ 0x20, 0x00, 0x11, 0xe3, /* tst r1, #0x20 */
+ 0xfc, 0xff, 0xff, 0x0a, /* beq .Lloop_thre */
+
+ /* ; Put character into Transmitter FIFO */
+ /* ; r1 = *r2++ */
+ 0x01, 0x10, 0xd2, 0xe4, /* ldrb r1, [r2], #1 */
+ /* ; UART_BASE[THR] = r1 */
+ 0x00, 0x10, 0x80, 0xe5, /* str r1, [r0, #0x0] */
+
+ /* ; Loop until end of preamble string */
+ 0x00, 0x00, 0x51, 0xe3, /* cmp r1, #0 */
+ 0xf8, 0xff, 0xff, 0x1a, /* bne .Lloop_preamble */
};
-/* ARM code for returning back to the bootrom */
+/* ARM code for returning from binary header back to BootROM */
static unsigned char kwboot_baud_code_binhdr_post[] = {
/* ; Return 0 - no error */
0x00, 0x00, 0xa0, 0xe3, /* mov r0, #0 */
@@ -1078,18 +1095,6 @@ kwboot_xmodem(int tty, const void *_img, size_t size, int baudrate)
return rc;
if (baudrate) {
- char buf[sizeof(kwb_baud_magic)];
-
- kwboot_printv("Waiting 1s for baudrate change magic\n");
- rc = kwboot_tty_recv(tty, buf, sizeof(buf), 1000);
- if (rc)
- return rc;
-
- if (memcmp(buf, kwb_baud_magic, sizeof(buf))) {
- errno = EPROTO;
- return -1;
- }
-
kwboot_printv("\nChanging baudrate back to 115200 Bd\n\n");
rc = kwboot_tty_change_baudrate(tty, 115200);
if (rc)
--
2.32.0
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