linux-kernel - Re: [PATCH] serial: sh-sci: Call device_set_wakeup

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Date: Tue, 23 Apr 2024 09:27:41 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Claudiu <claudiu.beznea@...on.dev>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, ulf.hansson@...aro.org, 
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org, 
	linux-pm@...r.kernel.org, Peng Fan <peng.fan@....com>
Subject: Re: [PATCH] serial: sh-sci: Call device_set_wakeup_path() for serial console

Hi Claudiu,

CC Peng

Thanks for your patch!

On Mon, Apr 22, 2024 at 1:11 PM Claudiu <claudiu.beznea@...on.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> In case the SCI is used as a UART console, no_console_suspend is
> available in bootargs and SCI is part of a software-controlled power
> domain we need to call device_set_wakeup_path(). This lets the power
> domain core code knows that this domain should not be powered off

know

> durring system suspend. Otherwise, the SCI power domain is turned off,

during

> nothing is printed while suspending and the suspend/resume process is
> blocked. This was detected on the RZ/G3S SoC while adding support
> for power domains.
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> ---
>  drivers/tty/serial/sh-sci.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> index 97031db26ae4..57a7f18e16e4 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -3441,8 +3441,12 @@ static __maybe_unused int sci_suspend(struct device *dev)
>  {
>         struct sci_port *sport = dev_get_drvdata(dev);
>
> -       if (sport)
> +       if (sport) {
> +               if (uart_console(&sport->port) && !console_suspend_enabled)
> +                       device_set_wakeup_path(dev);

device_set_awake_path(), as of commit 10bb4e4ab7dd3898 ("PM: sleep:
Add helpers to allow a device to remain powered-on") in v6.6
(although I'm still a bit puzzled about the difference).

> +
>                 uart_suspend_port(&sci_uart_driver, &sport->port);

I think it would be better to make this more general, and move the call
to the existing console_suspend_enabled handling in uart_suspend_port().

> +       }
>
>         return 0;
>  }

If this works, we can remove the console_suspend_enabled handling
from drivers/pmdomain/renesas/rmobile-sysc.c, and revert commit
309864dcf92b76fc ("genpd: imx: scu-pd: do not power off console if
no_console_suspend").

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds