imx-serial-excessive-status-clearing-on-break.patch
cc: Sasha Hauer <kernel@pengutronix.de>
We noticed that we were only able to communicate once with a GSM module
per session, if we powered down the module then the serial driver was
broken until reset, no traffic or /proc/interrupts activity could be
seen any more.
Volker noticed it was provoked by a long "break" seen on the wire when
the RX was not driven during powerdown, we discovered we could kill the
serial driver just by forcing RX low extenally for a little while.
I saw that the processing for BREAK in the driver gets too excited and
clears down all set bits in USR2, including that a character is pending.
This stops all further characters getting processed.
The attached one-liner makes the serial driver immortal against BREAK.
Signed-off-by: Andy Green <andy.green@txtr.com>
Signed-off-by: Volker Ernst <volker.ernst@txtr.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/drivers/serial/imx.c b/drivers/serial/imx.c
index 18130f1..c5b546a 100644
--- a/drivers/serial/imx.c
+++ b/drivers/serial/imx.c
@@ -440,7 +440,7 @@
temp = readl(sport->port.membase + USR2);
if (temp & USR2_BRCD) {
- writel(temp | USR2_BRCD, sport->port.membase + USR2);
+ writel(USR2_BRCD, sport->port.membase + USR2);
if (uart_handle_break(&sport->port))
continue;
}