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Message-ID: <5c49bc0f468e9fb5ae7ff7f53443fdb1fc3c77f2.camel@linuxfoundation.org>
Date: Mon, 23 Oct 2023 10:40:54 +0100
From: Richard Purdie <richard.purdie@...uxfoundation.org>
To: Tony Lindgren <tony@...mide.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@...el.com>,
Dhruva Gole <d-gole@...com>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
John Ogness <john.ogness@...utronix.de>,
Johan Hovold <johan@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Vignesh Raghavendra <vigneshr@...com>,
linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
Bruce Ashfield <bruce.ashfield@...il.com>,
Mikko Rapeli <mikko.rapeli@...aro.org>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Randy MacLeod <randy.macleod@...driver.com>
Subject: Re: [PATCH] serial: core: Fix runtime PM handling for pending tx
On Mon, 2023-10-23 at 10:48 +0300, Tony Lindgren wrote:
> 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")
> Reported-by: Richard Purdie <richard.purdie@...uxfoundation.org>
Tested-by: Richard Purdie <richard.purdie@...uxfoundation.org>
Thanks, I can confirm that since we added this into our builds/tests
we've not seen the serial data go missing.
Cheers,
Richard
> Cc: Bruce Ashfield <bruce.ashfield@...il.com>
> Cc: Mikko Rapeli <mikko.rapeli@...aro.org>
> Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
> Cc: Randy MacLeod <randy.macleod@...driver.com>
> Signed-off-by: Tony Lindgren <tony@...mide.com>
> ---
> 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
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -146,7 +146,7 @@ static void __uart_start(struct uart_state *state)
>
> /* 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;
> }
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