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From: Ulf Hansson <ulf.hansson@linaro.org>
Date: Thu, 25 Apr 2024 18:39:55 +0200
Message-ID: <CAPDyKFrC1HbUtnnGhJEG-fUH-DNw7En5Was6D=dND=tmFET7fA@mail.gmail.com>
Subject: Re: [RFT PATCH v2] serial: core: Call device_set_awake_path() for
 console port
To: Claudiu <claudiu.beznea@tuxon.dev>
Cc: gregkh@linuxfoundation.org, jirislaby@kernel.org, tony@atomide.com, 
	andriy.shevchenko@linux.intel.com, l.sanfilippo@kunbus.com, 
	tglx@linutronix.de, geert+renesas@glider.be, peng.fan@nxp.com, 
	linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, 
	linux-pm@vger.kernel.org, Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>, 
	Geert Uytterhoeven <geert@linux-m68k.org>
Content-Type: text/plain; charset="UTF-8"

On Thu, 25 Apr 2024 at 09:09, Claudiu <claudiu.beznea@tuxon.dev> wrote:
>
> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>
> In case the UART port is used as a console, no_console_suspend is
> available in bootargs and UART port is part of a software-controlled power
> domain we need to call device_set_awake_path(). This lets the power
> domain core code know that this domain should not be powered off
> during system suspend. Otherwise, the UART port power domain is turned off,
> nothing is printed while suspending and the suspend/resume process is
> blocked. This was detected on the Renesas RZ/G3S SoC while adding support
> for power domains.
>
> Based on code investigation, this issue is present on other SoCs (e.g.,
> Renesas R-Mobile A1 [1], IMX8QXP [2]) and different SoCs have particular
> implementation to handle it. Due to this the patch added the call of
> device_set_awake_path() in uart_suspend_port() instead of having it in
> the platform specific UART driver.
>
> [1] https://elixir.bootlin.com/linux/v6.9-rc5/source/drivers/pmdomain/renesas/rmobile-sysc.c#L116
> [2] https://elixir.bootlin.com/linux/v6.9-rc5/source/drivers/pmdomain/imx/scu-pd.c#L357
>
> Suggested-by: Ulf Hansson <ulf.hansson@linaro.org>
> Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>

At least conceptually this makes perfect sense to me. If it's the
correct place to put it, I trust others to know. Nevertheless, feel
free to add:

Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

Kind regards
Uffe

> ---
>
> Changes in v2:
> - used device_set_awake_path() instead of device_set_wakeup_path()
> - moved the support in uart_suspend_port() to make it generic for
>   other drivers
> - fixed typos in commit description
> - updated the commit description to reflect the new changes and the fact
>   that support may be applied to other SoCs
> - added Suggested-by tag; this was initially proposed by Ulf to move it
>   in the serial driver then Geert propose to have it more generic in
>   uart_suspend_port()
>
>
>  drivers/tty/serial/serial_core.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index d8d797a7a1e3..6270baab668c 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2409,6 +2409,7 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
>                         uport->ops->stop_rx(uport);
>                         uart_port_unlock_irq(uport);
>                 }
> +               device_set_awake_path(uport->dev);
>                 goto unlock;
>         }
>
> --
> 2.39.2
>