[Blackfin] serial driver: fix bug - cache the bits of the LSR on systems where the LSR is read-to-clear

Cache the bits of the LSR on systems where the LSR is read-to-clear
so that we can safely read the LSR in random places.  this fixes
older parts where break/framing/parity/overflow was not being detected
at all in PIO mode, and this fixes newer parts where
break/framing/parity/overflow was being reported all the time
without being cleared.

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/serial/bfin_5xx.c b/drivers/serial/bfin_5xx.c
index ca9ceaa113a2..af84984df775 100644
--- a/drivers/serial/bfin_5xx.c
+++ b/drivers/serial/bfin_5xx.c
@@ -216,8 +216,10 @@ static void bfin_serial_rx_chars(struct bfin_serial_port *uart)
         struct pt_regs *regs = get_irq_regs();
 #endif
 
-        ch = UART_GET_CHAR(uart);
         status = UART_GET_LSR(uart);
+        UART_CLEAR_LSR(uart);
+
+        ch = UART_GET_CHAR(uart);
         uart->port.icount.rx++;
 
 #ifdef CONFIG_KGDB_UART
@@ -335,7 +337,7 @@ static irqreturn_t bfin_serial_rx_int(int irq, void *dev_id)
         struct bfin_serial_port *uart = dev_id;
 
         spin_lock(&uart->port.lock);
-        while ((UART_GET_IER(uart) & ERBFI) && (UART_GET_LSR(uart) & DR))
+        while (UART_GET_LSR(uart) & DR)
                 bfin_serial_rx_chars(uart);
         spin_unlock(&uart->port.lock);
 
@@ -347,7 +349,7 @@ static irqreturn_t bfin_serial_tx_int(int irq, void *dev_id)
         struct bfin_serial_port *uart = dev_id;
 
         spin_lock(&uart->port.lock);
-        if ((UART_GET_IER(uart) & ETBEI) && (UART_GET_LSR(uart) & THRE))
+        if (UART_GET_LSR(uart) & THRE)
                 bfin_serial_tx_chars(uart);
         spin_unlock(&uart->port.lock);
 
@@ -428,6 +430,8 @@ static void bfin_serial_dma_rx_chars(struct bfin_serial_port *uart)
         int i, flg, status;
 
         status = UART_GET_LSR(uart);
+        UART_CLEAR_LSR(uart);
+
         uart->port.icount.rx += CIRC_CNT(uart->rx_dma_buf.head, uart->rx_dma_buf.tail, UART_XMIT_SIZE);;
 
         if (status & BI) {