serial: sprd: clear timeout interrupt only rather than all interrupts

commit 4350782570b919f254c1e083261a21c19fcaee90 upstream.

On Spreadtrum's serial device, nearly all of interrupts would be cleared
by hardware except timeout interrupt.  This patch removed the operation
of clearing all interrupt in irq handler, instead added an if statement
to check if the timeout interrupt is supposed to be cleared.

Wrongly clearing timeout interrupt would lead to uart data stay in rx
fifo, that means the driver cannot read them out anymore.

Signed-off-by: Lanqing Liu <lanqing.liu@spreadtrum.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
index cc1a55ee64034028d864638d7d7024009c05cb5a..747560feb63e9a6ca7dfbac8bd591769730bb327 100644 (file)
--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -63,6 +63,7 @@
 
 /* interrupt clear register */
 #define SPRD_ICLR              0x0014
+#define SPRD_ICLR_TIMEOUT      BIT(13)
 
 /* line control register */
 #define SPRD_LCR               0x0018
@@ -298,7 +299,8 @@ static irqreturn_t sprd_handle_irq(int irq, void *dev_id)
                return IRQ_NONE;
        }
 
-       serial_out(port, SPRD_ICLR, ~0);
+       if (ims & SPRD_IMSR_TIMEOUT)
+               serial_out(port, SPRD_ICLR, SPRD_ICLR_TIMEOUT);
 
        if (ims & (SPRD_IMSR_RX_FIFO_FULL |
                SPRD_IMSR_BREAK_DETECT | SPRD_IMSR_TIMEOUT))