From 89b8b8c121fe201862929709d451fecb24947676 Mon Sep 17 00:00:00 2001 From: Tony Lindgren Date: Thu, 5 Oct 2023 10:56:42 +0300 Subject: [PATCH] serial: core: Fix checks for tx runtime PM state Maximilian reported that surface_serial_hub serdev tx does not work during system suspend. During system suspend, runtime PM gets disabled in __device_suspend_late(), and tx is unable to wake-up the serial core port device that we use to check if tx is safe to start. Johan summarized the regression noting that serdev tx no longer always works as earlier when the serdev device is runtime PM active. The serdev device and the serial core controller devices are siblings of the serial port hardware device. The runtime PM usage count from serdev device does not propagate to the serial core device siblings, it only propagates to the parent. In addition to the tx issue for suspend, testing for the serial core port device can cause an unnecessary delay in enabling tx while waiting for the serial core port device to wake-up. The serial core port device wake-up is only needed to flush pending tx when the serial port hardware device was in runtime PM suspended state. To fix the regression, we need to check the runtime PM state of the parent serial port hardware device for tx instead of the serial core port device. As the serial port device drivers may or may not implement runtime PM, we need to also add a check for pm_runtime_enabled(). Reported-by: Maximilian Luz Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM") Signed-off-by: Tony Lindgren Reviewed-by: Andy Shevchenko Patchset: surface-sam --- drivers/tty/serial/serial_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 831d033611e6..e429ac42a12e 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -157,7 +157,7 @@ static void __uart_start(struct tty_struct *tty) * enabled, serial_port_runtime_resume() calls start_tx() again * after enabling the device. */ - if (pm_runtime_active(&port_dev->dev)) + if (!pm_runtime_enabled(port->dev) || pm_runtime_active(port->dev)) port->ops->start_tx(port); pm_runtime_mark_last_busy(&port_dev->dev); pm_runtime_put_autosuspend(&port_dev->dev); -- 2.42.0