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authorPeter Hurley <peter@hurleysoftware.com>2014-07-06 19:29:52 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-07-11 03:31:34 +0400
commitc557d392fbf5badd693ea1946a4317c87a26a716 (patch)
tree10b1369df578934fa8d43fbef7c69fb523ac5ab9 /drivers/tty/serial/sunzilog.c
parentcd3de83f147601356395b57a8673e9c5ff1e59d1 (diff)
downloadlinux-c557d392fbf5badd693ea1946a4317c87a26a716.tar.xz
serial: Test for no tx data on tx restart
Commit 717f3bbab3c7628736ef738fdbf3d9a28578c26c, 'serial_core: Fix conditional start_tx on ring buffer not empty' exposes an incorrect assumption in several drivers' start_tx methods; the tx ring buffer can, in fact, be empty when restarting tx while performing flow control. Affected drivers: sunsab.c ip22zilog.c pmac_zilog.c sunzilog.c m32r_sio.c imx.c Other in-tree serial drivers either are not affected or already test for empty tx ring buffer before transmitting. Test for empty tx ring buffer in start_tx() method, after transmitting x_char (if applicable). Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi> Cc: Seth Bollinger <sethb@digi.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Cc: stable <stable@vger.kernel.org> # 3.15 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial/sunzilog.c')
-rw-r--r--drivers/tty/serial/sunzilog.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/tty/serial/sunzilog.c b/drivers/tty/serial/sunzilog.c
index a85db8b87156..02df3940b95e 100644
--- a/drivers/tty/serial/sunzilog.c
+++ b/drivers/tty/serial/sunzilog.c
@@ -703,6 +703,8 @@ static void sunzilog_start_tx(struct uart_port *port)
} else {
struct circ_buf *xmit = &port->state->xmit;
+ if (uart_circ_empty(xmit))
+ return;
writeb(xmit->buf[xmit->tail], &channel->data);
ZSDELAY();
ZS_WSYNC(channel);