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Date: Sun, 6 Jul 2014 11:29:52 -0400
From: Peter Hurley <peter@...leysoftware.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
Peter Hurley <peter@...leysoftware.com>,
Seth Bollinger <sethb@...i.com>,
"David S. Miller" <davem@...emloft.net>,
Sam Ravnborg <sam@...nborg.org>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Subject: [PATCH 1/2] 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@....fi>
Cc: Seth Bollinger <sethb@...i.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Sam Ravnborg <sam@...nborg.org>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Peter Hurley <peter@...leysoftware.com>
---
drivers/tty/serial/imx.c | 3 +++
drivers/tty/serial/ip22zilog.c | 2 ++
drivers/tty/serial/m32r_sio.c | 8 +++++---
drivers/tty/serial/pmac_zilog.c | 3 +++
drivers/tty/serial/sunsab.c | 3 +++
drivers/tty/serial/sunzilog.c | 2 ++
6 files changed, 18 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 3b6c1a2..23c1dae 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -563,6 +563,9 @@ static void imx_start_tx(struct uart_port *port)
struct imx_port *sport = (struct imx_port *)port;
unsigned long temp;
+ if (uart_circ_empty(&port.state->xmit))
+ return;
+
if (USE_IRDA(sport)) {
/* half duplex in IrDA mode; have to disable receive mode */
temp = readl(sport->port.membase + UCR4);
diff --git a/drivers/tty/serial/ip22zilog.c b/drivers/tty/serial/ip22zilog.c
index 1efd4c3..99b7b86 100644
--- a/drivers/tty/serial/ip22zilog.c
+++ b/drivers/tty/serial/ip22zilog.c
@@ -603,6 +603,8 @@ static void ip22zilog_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);
diff --git a/drivers/tty/serial/m32r_sio.c b/drivers/tty/serial/m32r_sio.c
index 68f2c53..5702828 100644
--- a/drivers/tty/serial/m32r_sio.c
+++ b/drivers/tty/serial/m32r_sio.c
@@ -266,9 +266,11 @@ static void m32r_sio_start_tx(struct uart_port *port)
if (!(up->ier & UART_IER_THRI)) {
up->ier |= UART_IER_THRI;
serial_out(up, UART_IER, up->ier);
- serial_out(up, UART_TX, xmit->buf[xmit->tail]);
- xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
- up->port.icount.tx++;
+ if (!uart_circ_empty(xmit)) {
+ serial_out(up, UART_TX, xmit->buf[xmit->tail]);
+ xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+ up->port.icount.tx++;
+ }
}
while((serial_in(up, UART_LSR) & UART_EMPTY) != UART_EMPTY);
#else
diff --git a/drivers/tty/serial/pmac_zilog.c b/drivers/tty/serial/pmac_zilog.c
index 8193635..f7ad5b9 100644
--- a/drivers/tty/serial/pmac_zilog.c
+++ b/drivers/tty/serial/pmac_zilog.c
@@ -653,6 +653,8 @@ static void pmz_start_tx(struct uart_port *port)
} else {
struct circ_buf *xmit = &port->state->xmit;
+ if (uart_circ_empty(xmit))
+ goto out;
write_zsdata(uap, xmit->buf[xmit->tail]);
zssync(uap);
xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
@@ -661,6 +663,7 @@ static void pmz_start_tx(struct uart_port *port)
if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
uart_write_wakeup(&uap->port);
}
+ out:
pmz_debug("pmz: start_tx() done.\n");
}
diff --git a/drivers/tty/serial/sunsab.c b/drivers/tty/serial/sunsab.c
index 80a58ec..2f57df9 100644
--- a/drivers/tty/serial/sunsab.c
+++ b/drivers/tty/serial/sunsab.c
@@ -427,6 +427,9 @@ static void sunsab_start_tx(struct uart_port *port)
struct circ_buf *xmit = &up->port.state->xmit;
int i;
+ if (uart_circ_empty(xmit))
+ return;
+
up->interrupt_mask1 &= ~(SAB82532_IMR1_ALLS|SAB82532_IMR1_XPR);
writeb(up->interrupt_mask1, &up->regs->w.imr1);
diff --git a/drivers/tty/serial/sunzilog.c b/drivers/tty/serial/sunzilog.c
index a85db8b..02df394 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);
--
2.0.0
--
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