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tty: xuartps: Force enable the UART in xuartps_console_write

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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>
This commit is contained in:
Lars-Peter Clausen 2013-10-17 14:08:09 -07:00 committed by Greg Kroah-Hartman
parent 85baf542d5
commit d3755f5e6c
1 changed files with 11 additions and 1 deletions
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12
drivers/tty/serial/xilinx_uartps.c
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@ -953,7 +953,7 @@ static void xuartps_console_write(struct console *co, const char *s,
{ {
struct uart_port *port = &xuartps_port[co->index]; struct uart_port *port = &xuartps_port[co->index];
unsigned long flags; unsigned long flags;
unsigned int imr; unsigned int imr, ctrl;
int locked = 1; int locked = 1;
if (oops_in_progress) 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); imr = xuartps_readl(XUARTPS_IMR_OFFSET);
xuartps_writel(imr, XUARTPS_IDR_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); uart_console_write(port, s, count, xuartps_console_putchar);
xuartps_console_wait_tx(port); xuartps_console_wait_tx(port);
xuartps_writel(ctrl, XUARTPS_CR_OFFSET);
/* restore interrupt state, it seems like there may be a h/w bug /* restore interrupt state, it seems like there may be a h/w bug
* in that the interrupt enable register should not need to be * in that the interrupt enable register should not need to be
* written based on the data sheet * written based on the data sheet