Blackfin: fix up UART status bit handling

Some Blackfin UARTs are read-to-clear while others are write-to-clear.
This can cause problems when we poll the LSR and then later try and handle
any errors detected.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

diff --git a/cpu/blackfin/serial.c b/cpu/blackfin/serial.c
index 406d9d023d6805c6bc4ea6837c50e9fbc11bb694..0d6f377c058328ca8e875a5a3ee406a1c380c680 100644 (file)
--- a/cpu/blackfin/serial.c
+++ b/cpu/blackfin/serial.c
@@ -35,6 +35,32 @@
 
 #include "serial.h"
 
+#ifdef CONFIG_DEBUG_SERIAL
+uint16_t cached_lsr[256];
+uint16_t cached_rbr[256];
+size_t cache_count;
+
+/* 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;
+}
+#else
+static inline uint16_t uart_lsr_read(void) { return *pUART_LSR; }
+static inline void uart_lsr_clear(void) { *pUART_LSR = -1; }
+#endif
+
 /* Symbol for our assembly to call. */
 void serial_set_baud(uint32_t baud)
 {
@@ -61,6 +87,12 @@ 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 +105,7 @@ 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 */
@@ -83,38 +115,54 @@ 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)
 {
-       uint16_t uart_lsr_val, uart_rbr_val;
+       uint16_t uart_rbr_val;
 
        /* wait for data ! */
        while (!serial_tstc())
                continue;
 
-       /* clear the status and grab the new byte */
-       uart_lsr_val = *pUART_LSR;
+       /* grab the new byte */
        uart_rbr_val = *pUART_RBR;
 
+#ifdef CONFIG_DEBUG_SERIAL
+       /* grab & clear the LSR */
+       uint16_t uart_lsr_val = uart_lsr_read();
+
+       cached_lsr[cache_count] = uart_lsr_val;
+       cached_rbr[cache_count] = uart_rbr_val;
+       cache_count = (cache_count + 1) % ARRAY_SIZE(cached_lsr);
+
        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);
+               uint16_t dll, dlh;
+               printf("\n[SERIAL ERROR]\n");
+               ACCESS_LATCH();
+               dll = *pUART_DLL;
+               dlh = *pUART_DLH;
+               ACCESS_PORT_IER();
+               printf("\tDLL=0x%x DLH=0x%x\n", dll, dlh);
+               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);
                return -1;
        }
+#endif
+       uart_lsr_clear();
 
-       return uart_rbr_val & 0xFF;
+       return uart_rbr_val;
 }
 
 void serial_puts(const char *s)