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authorJason Wessel <jason.wessel@windriver.com>2012-08-12 07:16:43 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-08-26 15:00:43 -0700
commita8e480349f91581d93eff8728fc41cbcd1c3eca1 (patch)
tree90dce029675ff127769cdfb0c0fa580aa4b92e9c
parent952227d5c4d522502b7b815b16be6e991bbaeaed (diff)
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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. Signed-off-by: Jason Wessel <jason.wessel@windriver.com> Cc: Alan Cox <alan@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/tty/serial/pmac_zilog.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/drivers/tty/serial/pmac_zilog.c b/drivers/tty/serial/pmac_zilog.c
index 654755a990d..333c8d012b0 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)