From: Lars-Peter Clausen <[email protected]> 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 <[email protected]> Signed-off-by: John Linn <[email protected]> Signed-off-by: Michal Simek <[email protected]> Signed-off-by: Soren Brinkmann <[email protected]> --- 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 <[email protected]> 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 <[email protected]> Signed-off-by: John Linn <[email protected]> Signed-off-by: Michal Simek <[email protected]> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
