6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tony Lindgren tony@atomide.com
commit 6f699743aebf07538e506a46c5965eb8bdd2c716 upstream.
Richard reported that a serial port may end up sometimes with tx data pending in the buffer for long periods of time.
Turns out we bail out early on any errors from pm_runtime_get(), including -EINPROGRESS. To fix the issue, we need to ignore -EINPROGRESS as we only care about the runtime PM usage count at this point. We check for an active runtime PM state later on for tx.
Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM") Cc: stable stable@kernel.org Reported-by: Richard Purdie richard.purdie@linuxfoundation.org Cc: Bruce Ashfield bruce.ashfield@gmail.com Cc: Mikko Rapeli mikko.rapeli@linaro.org Cc: Paul Gortmaker paul.gortmaker@windriver.com Cc: Randy MacLeod randy.macleod@windriver.com Signed-off-by: Tony Lindgren tony@atomide.com Tested-by: Richard Purdie richard.purdie@linuxfoundation.org Link: https://lore.kernel.org/r/20231023074856.61896-1-tony@atomide.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/serial_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -146,7 +146,7 @@ static void __uart_start(struct uart_sta
/* Increment the runtime PM usage count for the active check below */ err = pm_runtime_get(&port_dev->dev); - if (err < 0) { + if (err < 0 && err != -EINPROGRESS) { pm_runtime_put_noidle(&port_dev->dev); return; }