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Don't loop infinitely long on serial comm failures 

If serial uart (8250/16x50) takes abnormally long to respond, give
up on logging to serial console and instead let the system boot.

Also reference bit in LSR register with correct name.

Change-Id: I3796efc3e8690425f04a130af4bc99541b64d335
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/611
Tested-by: build bot (Jenkins)
Reviewed-by: Peter Stuge <peter@stuge.se>
This commit is contained in:
Kyösti Mälkki 2012-02-07 20:50:22 +02:00 committed by Peter Stuge
parent 7f782a8f0b
commit 9dd3ef165a
1 changed files with 22 additions and 9 deletions
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31
src/lib/uart8250.c
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@ -29,21 +29,30 @@
/* Should support 8250, 16450, 16550, 16550A type UARTs */ /* Should support 8250, 16450, 16550, 16550A type UARTs */
/* Expected character delay at 1200bps is 9ms for a working UART
* and no flow-control. Assume UART as stuck if shift register
* or FIFO takes more than 50ms per character to appear empty.
*
* Estimated that inb() from UART takes 1 microsecond.
*/
#define SINGLE_CHAR_TIMEOUT (50 * 1000)
#define FIFO_TIMEOUT (16 * SINGLE_CHAR_TIMEOUT)
static inline int uart8250_can_tx_byte(unsigned base_port) static inline int uart8250_can_tx_byte(unsigned base_port)
{ {
return inb(base_port + UART_LSR) & UART_MSR_DSR; return inb(base_port + UART_LSR) & UART_LSR_THRE;
} }
static inline void uart8250_wait_to_tx_byte(unsigned base_port) static inline void uart8250_wait_to_tx_byte(unsigned base_port)
{ {
while(!uart8250_can_tx_byte(base_port)) unsigned long int i = SINGLE_CHAR_TIMEOUT;
; while (i-- && !uart8250_can_tx_byte(base_port));
} }
static inline void uart8250_wait_until_sent(unsigned base_port) static inline void uart8250_wait_until_sent(unsigned base_port)
{ {
while(!(inb(base_port + UART_LSR) & UART_LSR_TEMT)) unsigned long int i = FIFO_TIMEOUT;
; while (i-- && !(inb(base_port + UART_LSR) & UART_LSR_TEMT));
} }
void uart8250_tx_byte(unsigned base_port, unsigned char data) void uart8250_tx_byte(unsigned base_port, unsigned char data)
@ -64,9 +73,13 @@ int uart8250_can_rx_byte(unsigned base_port)
unsigned char uart8250_rx_byte(unsigned base_port) unsigned char uart8250_rx_byte(unsigned base_port)
{ {
while(!uart8250_can_rx_byte(base_port)) unsigned long int i = SINGLE_CHAR_TIMEOUT;
; while (i-- && !uart8250_can_rx_byte(base_port));
return inb(base_port + UART_RBR);
if (i)
return inb(base_port + UART_RBR);
else
return 0x0;
} }
void uart8250_init(unsigned base_port, unsigned divisor) void uart8250_init(unsigned base_port, unsigned divisor)
@ -83,7 +96,7 @@ void uart8250_init(unsigned base_port, unsigned divisor)
/* DLAB on */ /* DLAB on */
outb(UART_LCR_DLAB | CONFIG_TTYS0_LCS, base_port + UART_LCR); outb(UART_LCR_DLAB | CONFIG_TTYS0_LCS, base_port + UART_LCR);
/* Set Baud Rate Divisor. 12 ==> 115200 Baud */ /* Set Baud Rate Divisor. 12 ==> 9600 Baud */
outb(divisor & 0xFF, base_port + UART_DLL); outb(divisor & 0xFF, base_port + UART_DLL);
outb((divisor >> 8) & 0xFF, base_port + UART_DLM); outb((divisor >> 8) & 0xFF, base_port + UART_DLM);