From 4422e6fe13eff3fc4337dedc76f6830e1a3b4e1a Mon Sep 17 00:00:00 2001 From: Jason Wessel Date: Sun, 12 Aug 2012 07:16:43 -0500 Subject: [PATCH] pmac_zilog,kdb: Fix console poll hook to return instead of loop commit 38f8eefccf3a23c4058a570fa2938a4f553cf8e0 upstream. kdb <-> kgdb transitioning does not work properly with this UART driver because the get character routine loops indefinitely as opposed to returning NO_POLL_CHAR per the expectation of the KDB I/O driver API. The symptom is a kernel hang when trying to switch debug modes. Cc: Alan Cox Signed-off-by: Jason Wessel Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/tty/serial/pmac_zilog.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/pmac_zilog.c b/drivers/tty/serial/pmac_zilog.c index 5acd24a27d08..086f7fe63f94 100644 --- a/drivers/tty/serial/pmac_zilog.c +++ b/drivers/tty/serial/pmac_zilog.c @@ -1407,10 +1407,16 @@ static int pmz_verify_port(struct uart_port *port, struct serial_struct *ser) static int pmz_poll_get_char(struct uart_port *port) { struct uart_pmac_port *uap = (struct uart_pmac_port *)port; + int tries = 2; - while ((read_zsreg(uap, R0) & Rx_CH_AV) == 0) - udelay(5); - return read_zsdata(uap); + while (tries) { + if ((read_zsreg(uap, R0) & Rx_CH_AV) != 0) + return read_zsdata(uap); + if (tries--) + udelay(5); + } + + return NO_POLL_CHAR; } static void pmz_poll_put_char(struct uart_port *port, unsigned char c) -- 2.39.5