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Date: Thu, 25 Apr 2024 12:50:16 +0300
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Claudiu <claudiu.beznea@tuxon.dev>
Cc: gregkh@linuxfoundation.org, jirislaby@kernel.org, tony@atomide.com,
	l.sanfilippo@kunbus.com, tglx@linutronix.de,
	geert+renesas@glider.be, ulf.hansson@linaro.org, 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>
Subject: Re: [RFT PATCH v2] serial: core: Call device_set_awake_path() for
 console port
Message-ID: <ZionWJ7ods60zuYX@smile.fi.intel.com>
References: <20240425070936.547100-1-claudiu.beznea.uj@bp.renesas.com>
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Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo

On Thu, Apr 25, 2024 at 10:09:36AM +0300, Claudiu 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

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@linaro.org>
> Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.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@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko