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Subject[PATCH 06/10] tty: xuartps: Force enable the UART in xuartps_console_write
Date
From: Lars-Peter Clausen <lars@metafoo.de>

It is possible that under certain circumstances xuartps_console_write is entered
while the UART disabled. When this happens the code will busy loop in
xuartps_console_putchar, since the character is never written and the TXEMPTY
flag is never set. The result is a system lockup. This patch force enables the
UART for the duration of xuartps_console_write to avoid this.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: John Linn <john.linn@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
---
Squashed from these original patches:
tty: xuartps: Force enable the UART in xuartps_console_write

It is possible that under certain circumstances xuartps_console_write is entered
while the UART disabled. When this happens the code will busy loop in
xuartps_console_putchar, since the character is never written and the TXEMPTY
flag is never set. The result is a system lockup. This patch force enables the
UART for the duration of xuartps_console_write to avoid this.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

and

tty: xuartps: Fix bad register write in console_write

The commit:
serial: xilinx_uartps: Force enable the UART in xuartps_console_write
(sha1: d21aec67c1c782314d20b3d619e76cf8aae593dc)
caused a new bug as the write to the control register had
the offset and the value to write reversed.

Reported-by: Jason Andrews <jasona@cadence.com>
Signed-off-by: John Linn <john.linn@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
---
drivers/tty/serial/xilinx_uartps.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 6e8ec6e9d5a2..fdc739b55eb3 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -953,7 +953,7 @@ static void xuartps_console_write(struct console *co, const char *s,
{
struct uart_port *port = &xuartps_port[co->index];
unsigned long flags;
- unsigned int imr;
+ unsigned int imr, ctrl;
int locked = 1;

if (oops_in_progress)
@@ -965,9 +965,19 @@ static void xuartps_console_write(struct console *co, const char *s,
imr = xuartps_readl(XUARTPS_IMR_OFFSET);
xuartps_writel(imr, XUARTPS_IDR_OFFSET);

+ /*
+ * Make sure that the tx part is enabled. Set the TX enable bit and
+ * clear the TX disable bit to enable the transmitter.
+ */
+ ctrl = xuartps_readl(XUARTPS_CR_OFFSET);
+ xuartps_writel((ctrl & ~XUARTPS_CR_TX_DIS) | XUARTPS_CR_TX_EN,
+ XUARTPS_CR_OFFSET);
+
uart_console_write(port, s, count, xuartps_console_putchar);
xuartps_console_wait_tx(port);

+ xuartps_writel(ctrl, XUARTPS_CR_OFFSET);
+
/* restore interrupt state, it seems like there may be a h/w bug
* in that the interrupt enable register should not need to be
* written based on the data sheet
--
1.8.4.1


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