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authorAndy Shevchenko <andriy.shevchenko@linux.intel.com>2016-08-31 19:46:55 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-10-22 12:06:46 +0200
commitfedf90584600c18be041d8a38c0024e4590c9643 (patch)
parent0c33f651585ccd1d07875d2a3a71a0c11520cb3b (diff)
serial: 8250_port: fix runtime PM use in __do_stop_tx_rs485()
commit b3965767d86cf4534dfe1affbde0453d3224ed7f upstream. There are calls to serial8250_rpm_{get|put}() in __do_stop_tx_rs485() that are certainly placed in a wrong location. I dunno how it had been tested with runtime PM enabled because it is obvious "sleep in atomic context" error. Besides that serial8250_rpm_get() is called immediately after an IO just happened. It implies that the device is already powered on, see implementation of serial8250_em485_rts_after_send() and serial8250_clear_fifos() for the details. There is no bug have been seen due to, as I can guess, use of auto suspend mode when scheduled transaction to suspend is invoked quite lately than it's needed for a few writes to the port. It might be possible to trigger a warning if stop_tx_timer fires when device is suspended. Refactor the code to use runtime PM only in case of timer function. Fixes: 0c66940d584d ("tty/serial/8250: fix RS485 half-duplex RX") Cc: "Matwey V. Kornilov" <matwey@sai.msu.ru> Tested-by: Yegor Yefremov <yegorslists@googlemail.com> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 5 insertions, 6 deletions
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index d4036038a4dd..427dd789c0e5 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1415,12 +1415,8 @@ static void __do_stop_tx_rs485(struct uart_8250_port *p)
if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
- serial8250_rpm_get(p);
serial_port_out(&p->port, UART_IER, p->ier);
- serial8250_rpm_put(p);
@@ -1430,6 +1426,7 @@ static void serial8250_em485_handle_stop_tx(unsigned long arg)
struct uart_8250_em485 *em485 = p->em485;
unsigned long flags;
+ serial8250_rpm_get(p);
spin_lock_irqsave(&p->port.lock, flags);
if (em485 &&
em485->active_timer == &em485->stop_tx_timer) {
@@ -1437,6 +1434,7 @@ static void serial8250_em485_handle_stop_tx(unsigned long arg)
em485->active_timer = NULL;
spin_unlock_irqrestore(&p->port.lock, flags);
+ serial8250_rpm_put(p);
static void __stop_tx_rs485(struct uart_8250_port *p)
@@ -1476,7 +1474,7 @@ static inline void __stop_tx(struct uart_8250_port *p)
unsigned char lsr = serial_in(p, UART_LSR);
* To provide required timeing and allow FIFO transfer,
- * __stop_tx_rs485 must be called only when both FIFO and
+ * __stop_tx_rs485() must be called only when both FIFO and
* shift register are empty. It is for device driver to enable
* interrupt on TEMT.
@@ -1485,9 +1483,10 @@ static inline void __stop_tx(struct uart_8250_port *p)
em485->active_timer = NULL;
+ __stop_tx_rs485(p);
- __stop_tx_rs485(p);
static void serial8250_stop_tx(struct uart_port *port)