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authorLars-Peter Clausen <lars@metafoo.de>2013-10-17 14:08:09 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-10-19 19:47:38 -0700
commitd3755f5e6cd222cd5aff949228d32aa8446023a5 (patch)
tree56b68cd0b26533e32217333e5e0ff4cfa460ec63 /drivers/tty
parent85baf542d54ec321642194b0ebfa7316e3190dc2 (diff)
downloadlinux-linaro-stable-d3755f5e6cd222cd5aff949228d32aa8446023a5.tar.gz
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> 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/xilinx_uartps.c12
1 files changed, 11 insertions, 1 deletions
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