[U-Boot-Users] [PATCH/review] Blackfin: add error debug to serial driver

[Mike Frysinger]

This adds a new CONFIG_DEBUG_SERIAL define so that people can figure out
if/when their serial port is hitting errors.

Signed-off-by: Mike Frysinger <vapier at gentoo.org>
---
 cpu/blackfin/serial.c |   57 +++++++++++++++++++++++++++++++++++++++++-------
 1 files changed, 48 insertions(+), 9 deletions(-)

diff --git a/cpu/blackfin/serial.c b/cpu/blackfin/serial.c
index 0dfee51..f538bba 100644
--- a/cpu/blackfin/serial.c
+++ b/cpu/blackfin/serial.c
@@ -35,6 +35,29 @@
 
 #include "serial.h"
 
+#ifdef CONFIG_DEBUG_SERIAL
+uint16_t cached_lsr[256];
+uint16_t cached_rbr[256];
+size_t cache_count;
+#endif
+
+/* The LSR is read-to-clear on some parts, so we have to make sure status
+ * bits aren't inadvertently lost when doing various tests.
+ */
+static uint16_t uart_lsr_save;
+static uint16_t uart_lsr_read(void)
+{
+	uint16_t lsr = *pUART_LSR;
+	uart_lsr_save |= (lsr & (OE|PE|FE|BI));
+	return lsr | uart_lsr_save;
+}
+/* Just do the clear for everyone since it can't hurt. */
+static void uart_lsr_clear(void)
+{
+	uart_lsr_save = 0;
+	*pUART_LSR |= -1;
+}
+
 /* Symbol for our assembly to call. */
 void serial_set_baud(uint32_t baud)
 {
@@ -61,6 +84,12 @@ int serial_init(void)
 {
 	serial_initialize();
 	serial_setbrg();
+	uart_lsr_clear();
+#ifdef CONFIG_DEBUG_SERIAL
+	cache_count = 0;
+	memset(cached_lsr, 0x00, sizeof(cached_lsr));
+	memset(cached_rbr, 0x00, sizeof(cached_rbr));
+#endif
 	return 0;
 }
 
@@ -73,7 +102,7 @@ void serial_putc(const char c)
 	WATCHDOG_RESET();
 
 	/* wait for the hardware fifo to clear up */
-	while (!(*pUART_LSR & THRE))
+	while (!(uart_lsr_read() & THRE))
 		continue;
 
 	/* queue the character for transmission */
@@ -83,14 +112,14 @@ void serial_putc(const char c)
 	WATCHDOG_RESET();
 
 	/* wait for the byte to be shifted over the line */
-	while (!(*pUART_LSR & TEMT))
+	while (!(uart_lsr_read() & TEMT))
 		continue;
 }
 
 int serial_tstc(void)
 {
 	WATCHDOG_RESET();
-	return (*pUART_LSR & DR) ? 1 : 0;
+	return (uart_lsr_read() & DR) ? 1 : 0;
 }
 
 int serial_getc(void)
@@ -102,15 +131,25 @@ int serial_getc(void)
 		continue;
 
 	/* clear the status and grab the new byte */
-	uart_lsr_val = *pUART_LSR;
+	uart_lsr_val = uart_lsr_read();
 	uart_rbr_val = *pUART_RBR;
 
+#ifdef CONFIG_DEBUG_SERIAL
+	cached_lsr[cache_count] = uart_lsr_val;
+	cached_rbr[cache_count] = uart_rbr_val;
+	cache_count = (cache_count + 1) % ARRAY_SIZE(cached_lsr);
+#endif
+
 	if (uart_lsr_val & (OE|PE|FE|BI)) {
-		/* Some parts are read-to-clear while others are
-		 * write-to-clear.  Just do the write for everyone
-		 * since it cant hurt (other than code size).
-		 */
-		*pUART_LSR = (OE|PE|FE|BI);
+#ifdef CONFIG_DEBUG_SERIAL
+		printf("\n[SERIAL ERROR]\n");
+		do {
+			--cache_count;
+			printf("\t%3i: RBR=0x%02x LSR=0x%02x\n", cache_count,
+				cached_rbr[cache_count], cached_lsr[cache_count]);
+		} while (cache_count > 0);
+#endif
+		uart_lsr_clear();
 		return -1;
 	}
 
-- 
1.5.4.2