[PATCH 3.18 27/49] serial: omap: fix runtime-pm handling on unbind

From: Greg Kroah-Hartman
Date: Thu May 18 2017 - 09:18:14 EST

3.18-stable review patch. If anyone has any objections, please let me know.


From: Johan Hovold <johan@xxxxxxxxxx>

commit 099bd73dc17ed77aa8c98323e043613b6e8f54fc upstream.

An unbalanced and misplaced synchronous put was used to suspend the
device on driver unbind, something which with a likewise misplaced
pm_runtime_disable leads to external aborts when an open port is being

Unhandled fault: external abort on non-linefetch (0x1028) at 0xfa024010
[<c046e760>] (serial_omap_set_mctrl) from [<c046a064>] (uart_update_mctrl+0x50/0x60)
[<c046a064>] (uart_update_mctrl) from [<c046a400>] (uart_shutdown+0xbc/0x138)
[<c046a400>] (uart_shutdown) from [<c046bd2c>] (uart_hangup+0x94/0x190)
[<c046bd2c>] (uart_hangup) from [<c045b760>] (__tty_hangup+0x404/0x41c)
[<c045b760>] (__tty_hangup) from [<c045b794>] (tty_vhangup+0x1c/0x20)
[<c045b794>] (tty_vhangup) from [<c046ccc8>] (uart_remove_one_port+0xec/0x260)
[<c046ccc8>] (uart_remove_one_port) from [<c046ef4c>] (serial_omap_remove+0x40/0x60)
[<c046ef4c>] (serial_omap_remove) from [<c04845e8>] (platform_drv_remove+0x34/0x4c)

Fix this up by resuming the device before deregistering the port and by
suspending and disabling runtime pm only after the port has been

Also make sure to disable autosuspend before disabling runtime pm so
that the usage count is balanced and device actually suspended before

Note that due to a negative autosuspend delay being set in probe, the
unbalanced put would actually suspend the device on first driver unbind,
while rebinding and again unbinding would result in a negative

Fixes: 7e9c8e7dbf3b ("serial: omap: make sure to suspend device before remove")
Cc: Felipe Balbi <balbi@xxxxxxxxxx>
Cc: Santosh Shilimkar <santosh.shilimkar@xxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/tty/serial/omap-serial.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1756,9 +1756,13 @@ static int serial_omap_remove(struct pla
struct uart_omap_port *up = platform_get_drvdata(dev);

+ pm_runtime_get_sync(up->dev);
+ uart_remove_one_port(&serial_omap_reg, &up->port);
+ pm_runtime_dont_use_autosuspend(up->dev);
- uart_remove_one_port(&serial_omap_reg, &up->port);
device_init_wakeup(&dev->dev, false);