linux-kernel - Re: [RFT PATCH v2] serial: core: Call device_set_awake

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Date: Thu, 25 Apr 2024 12:50:16 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Claudiu <claudiu.beznea@...on.dev>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, tony@...mide.com,
	l.sanfilippo@...bus.com, tglx@...utronix.de,
	geert+renesas@...der.be, ulf.hansson@...aro.org, peng.fan@....com,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-pm@...r.kernel.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [RFT PATCH v2] serial: core: Call device_set_awake_path() for
 console port

On Thu, Apr 25, 2024 at 10:09:36AM +0300, Claudiu wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@...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

No need to have the HTTP links into the kernel sources, you may simply refer to
the files in the source tree.

[1] drivers/pmdomain/renesas/rmobile-sysc.c:L116
[2] drivers/pmdomain/imx/scu-pd.c:L357

> Suggested-by: Ulf Hansson <ulf.hansson@...aro.org>
> Suggested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

The rest makes sense to me as we also have an internal hack to achieve
something similar in the case of Intel LPSS (8250_dw).

But I like Tony to comment on this, from my perspective it's good:
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

-- 
With Best Regards,
Andy Shevchenko