patch "serial: omap: fix runtime-pm handling on unbind" added to tty-testing

This is a note to let you know that I've just added the patch titled

serial: omap: fix runtime-pm handling on unbind

to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the tty-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From: Johan Hovold <[email protected]>
Date: Mon, 10 Apr 2017 11:21:38 +0200
Subject: serial: omap: fix runtime-pm handling on unbind

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 removed.

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 removed.

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

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 power.usage_count.

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

index a4734649a0f0..50f2c5a5e450 100644
@@ -1783,9 +1783,13 @@ static int serial_omap_remove(struct platform_device *dev)
 {
 	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);
 	pm_runtime_put_sync(up->dev);
 	pm_runtime_disable(up->dev);
-	uart_remove_one_port(&serial_omap_reg, &up->port);
 	pm_qos_remove_request(&up->pm_qos_request);
 	device_init_wakeup(&dev->dev, false);
 

2.12.2