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software/bios/boot: Allow frame reception to time out during serial b…
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…oot and do some cleanup/add comments.

Allowing the serial boot to time out during frame reception allows doing test on the Host side to
calibrate the minimum inter-frame delay and maximum payload length.

In the future, we should probably compute the CRC directly during frame reception and do the mempcpy
of frame N during the reception of frame N+1 to avoid these inter-frame constraints.
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@enjoy-digital
enjoy-digital committed Sep 29, 2021
1 parent 5a35aa9 commit 80cb53f
Showing 1 changed file with 98 additions and 48 deletions.
146 changes: 98 additions & 48 deletions litex/soc/software/bios/boot.c
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// This file is Copyright (c) 2014-2020 Florent Kermarrec <florent@enjoy-digital.fr>
// This file is Copyright (c) 2014-2021 Florent Kermarrec <florent@enjoy-digital.fr>
// This file is Copyright (c) 2013-2014 Sebastien Bourdeauducq <sb@m-labs.hk>
// This file is Copyright (c) 2018 Ewen McNeill <ewen@naos.co.nz>
// This file is Copyright (c) 2018 Felix Held <felix-github@felixheld.de>
Expand Down Expand Up @@ -104,20 +104,27 @@ void romboot(void)

#ifdef CSR_UART_BASE

static int check_ack(void)
{
int recognized;
static const char str[SFL_MAGIC_LEN] = SFL_MAGIC_ACK;
#define ACK_TIMEOUT_DELAY CONFIG_CLOCK_FREQUENCY/4
#define CMD_TIMEOUT_DELAY CONFIG_CLOCK_FREQUENCY/16

static void timer0_load(unsigned int value) {
timer0_en_write(0);
timer0_reload_write(0);
#ifndef CONFIG_DISABLE_DELAYS
timer0_load_write(CONFIG_CLOCK_FREQUENCY/4);
timer0_load_write(value);
#else
timer0_load_write(0);
#endif
timer0_en_write(1);
timer0_update_value_write(1);
}

static int check_ack(void)
{
int recognized;
static const char str[SFL_MAGIC_LEN] = SFL_MAGIC_ACK;

timer0_load(ACK_TIMEOUT_DELAY);
recognized = 0;
while(timer0_value_read()) {
if(uart_read_nonblock()) {
Expand All @@ -144,26 +151,26 @@ static int check_ack(void)
static uint32_t get_uint32(unsigned char* data)
{
return ((uint32_t) data[0] << 24) |
((uint32_t) data[1] << 16) |
((uint32_t) data[2] << 8) |
(uint32_t) data[3];
((uint32_t) data[1] << 16) |
((uint32_t) data[2] << 8) |
(uint32_t) data[3];
}

#define MAX_FAILED 5
#define MAX_FAILURES 256

/* Returns 1 if other boot methods should be tried */
int serialboot(void)
{
struct sfl_frame frame;
int failed;
int failures;
static const char str[SFL_MAGIC_LEN+1] = SFL_MAGIC_REQ;
const char *c;
int ack_status;

printf("Booting from serial...\n");
printf("Press Q or ESC to abort boot completely.\n");

/* Send the serialboot "magic" request to Host */
/* Send the serialboot "magic" request to Host and wait for ACK_OK */
c = str;
while(*c) {
uart_write(*c);
Expand All @@ -178,70 +185,113 @@ int serialboot(void)
printf("Cancelled\n");
return 0;
}
/* Assume ACK_OK */

failed = 0;
/* Assume ACK_OK */
failures = 0;
while(1) {
int i;
int actualcrc;
int goodcrc;
int timeout;
int computed_crc;
int received_crc;

/* Get one Frame */
frame.payload_length = uart_read();
frame.crc[0] = uart_read();
frame.crc[1] = uart_read();
frame.cmd = uart_read();
for(i=0;i<frame.payload_length;i++)
frame.payload[i] = uart_read();

/* Check Frame CRC (if CMD has a CRC) */
actualcrc = ((int)frame.crc[0] << 8)|(int)frame.crc[1];
goodcrc = crc16(&frame.cmd, frame.payload_length+1);
if(actualcrc != goodcrc) {
/* Clear out the RX buffer */
while (uart_read_nonblock()) uart_read();
failed++;
if(failed == MAX_FAILED) {
i = 0;
timeout = 1;
while((i == 0) || timer0_value_read()) {
if (uart_read_nonblock()) {
if (i == 0) {
timer0_load(CMD_TIMEOUT_DELAY);
frame.payload_length = uart_read();
}
if (i == 1) frame.crc[0] = uart_read();
if (i == 2) frame.crc[1] = uart_read();
if (i == 3) frame.cmd = uart_read();
if (i >= 4) {
frame.payload[i-4] = uart_read();
if (i == (frame.payload_length + 4 - 1)) {
timeout = 0;
break;
}
}
i++;
}
timer0_update_value_write(1);
}

/* Check Timeout */
if (timeout) {
/* Acknowledge the Timeout and continue with a new frame */
uart_write(SFL_ACK_ERROR);
continue;
}

/* Check Frame CRC */
received_crc = ((int)frame.crc[0] << 8)|(int)frame.crc[1];
computed_crc = crc16(&frame.cmd, frame.payload_length+1);
if(computed_crc != received_crc) {
/* Acknowledge the CRC error */
uart_write(SFL_ACK_CRCERROR);

/* Increment failures and exit when max is reached */
failures++;
if(failures == MAX_FAILURES) {
printf("Too many consecutive errors, aborting");
return 1;
}
uart_write(SFL_ACK_CRCERROR);
continue;
}

/* Execute Frame CMD */
switch(frame.cmd) {
/* On SFL_CMD_ABORT ... */
case SFL_CMD_ABORT:
failed = 0;
/* Reset failures */
failures = 0;
/* Acknowledge and exit */
uart_write(SFL_ACK_SUCCESS);
return 1;

/* On SFL_CMD_LOAD... */
case SFL_CMD_LOAD: {
char *writepointer;

failed = 0;
writepointer = (char *)(uintptr_t) get_uint32(&frame.payload[0]);
for(i=4;i<frame.payload_length;i++)
*(writepointer++) = frame.payload[i];
if (frame.cmd == SFL_CMD_LOAD)
uart_write(SFL_ACK_SUCCESS);
char *load_addr;

/* Reset failures */
failures = 0;

/* Copy payload */
load_addr = (char *)(uintptr_t) get_uint32(&frame.payload[0]);
memcpy(load_addr, &frame.payload[4], frame.payload_length);

/* Acknowledge and continue */
uart_write(SFL_ACK_SUCCESS);
break;
}
/* On SFL_CMD_ABORT ... */
case SFL_CMD_JUMP: {
uint32_t addr;
uint32_t jump_addr;

failed = 0;
addr = get_uint32(&frame.payload[0]);
/* Reset failures */
failures = 0;

/* Acknowledge and jump */
uart_write(SFL_ACK_SUCCESS);
boot(0, 0, 0, addr);
jump_addr = get_uint32(&frame.payload[0]);
boot(0, 0, 0, jump_addr);
break;
}
default:
failed++;
if(failed == MAX_FAILED) {
/* Increment failures */
failures++;

/* Acknowledge the UNKNOWN cmd */
uart_write(SFL_ACK_UNKNOWN);

/* Increment failures and exit when max is reached */
if(failures == MAX_FAILURES) {
printf("Too many consecutive errors, aborting");
return 1;
}
uart_write(SFL_ACK_UNKNOWN);

break;
}
}
Expand Down

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