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 <a...@linux.intel.com>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Jason Wessel <jason.wes...@windriver.com>
---
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 654755a..333c8d0 100644
--- a/drivers/tty/serial/pmac_zilog.c
+++ b/drivers/tty/serial/pmac_zilog.c
@@ -1348,10 +1348,16 @@ 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)
--
1.7.9.5
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