Patch set updated for coreboot: a529a47 Don't loop infinitely long on serial comm failures

[Stefan Reinauer]

Stefan Reinauer ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/826

-gerrit

commit a529a4718a63f7e0853b4c9dd32ec1c77cc7bb2c
Author: Stefan Reinauer 
Date:   Fri Mar 30 16:19:31 2012 -0700

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.

Signed-off-by: Kyösti Mälkki

Ported from 9dd3ef165a1bf1bc404056d3e54337de1a15ac90 to
    uart8250mem.c:
    Signed-off-by: Stefan Reinauer

Change-Id: Iaca4f57389c887110e6406d45053935891c96838
---
 src/lib/uart8250mem.c |   32 +++++++++++++++++++++++---------
 1 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/src/lib/uart8250mem.c b/src/lib/uart8250mem.c
index a38623e..b98cb0e 100644
--- a/src/lib/uart8250mem.c
+++ b/src/lib/uart8250mem.c
@@ -27,24 +27,34 @@
 #if !defined(__SMM__) && !defined(__PRE_RAM__)
 #include <device/device.h>
 #endif
+#include <delay.h>

/* 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.
+ */
+#define SINGLE_CHAR_TIMEOUT	(50 * 1000)
+#define FIFO_TIMEOUT		(16 * SINGLE_CHAR_TIMEOUT)
+
 static inline int uart8250_mem_can_tx_byte(unsigned base_port)
 {
-	return read8(base_port + UART_LSR) & UART_MSR_DSR;
+	return read8(base_port + UART_LSR) & UART_LSR_THRE;
 }

static inline void uart8250_mem_wait_to_tx_byte(unsigned base_port)
 {
-	while(!uart8250_mem_can_tx_byte(base_port))
-		;
+	unsigned long int i = SINGLE_CHAR_TIMEOUT;
+	while(i-- && !uart8250_mem_can_tx_byte(base_port))
+		udelay(1);
 }

static inline void uart8250_mem_wait_until_sent(unsigned base_port)
 {
-	while(!(read8(base_port + UART_LSR) & UART_LSR_TEMT))
-		;
+	unsigned long int i = FIFO_TIMEOUT;
+	while(i-- && !(read8(base_port + UART_LSR) & UART_LSR_TEMT))
+		udelay(1);
 }

void uart8250_mem_tx_byte(unsigned base_port, unsigned char data)
@@ -65,9 +75,13 @@ int uart8250_mem_can_rx_byte(unsigned base_port)

unsigned char uart8250_mem_rx_byte(unsigned base_port)
 {
-	while(!uart8250_mem_can_rx_byte(base_port))
-		;
-	return read8(base_port + UART_RBR);
+	unsigned long int i = SINGLE_CHAR_TIMEOUT;
+	while(i-- && !uart8250_mem_can_rx_byte(base_port))
+		udelay(1);
+	if (i)
+		return read8(base_port + UART_RBR);
+	else
+		return 0x0;
 }

void uart8250_mem_init(unsigned base_port, unsigned divisor)
@@ -83,7 +97,7 @@ void uart8250_mem_init(unsigned base_port, unsigned divisor)
    /* DLAB on */
    write8(base_port + UART_LCR, UART_LCR_DLAB | CONFIG_TTYS0_LCS);

-	/* Set Baud Rate Divisor. 12 ==> 115200 Baud */
+	/* Set Baud Rate Divisor. 12 ==> 9600 Baud */
    write8(base_port + UART_DLL, divisor & 0xFF);
    write8(base_port + UART_DLM, (divisor >> 8) & 0xFF);