linux-kernel - Re: [PATCH v3 4/5] drm/panfrost: devfreq: set opp to the recommended one to configure and enable regulator

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Date:   Tue, 6 Sep 2022 10:47:38 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Clément Péron <peron.clem@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Steven Price <steven.price@....com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Bjorn Andersson <andersson@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Arnd Bergmann <arnd@...db.de>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Vinod Koul <vkoul@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 4/5] drm/panfrost: devfreq: set opp to the recommended
 one to configure and enable regulator

Your subject is 87 columns long, better to squeeze it a bit.

On 05-09-22, 19:16, Clément Péron wrote:
> devm_pm_opp_set_regulators() doesn't enable regulator, which make
> regulator framework switching it off during regulator_late_cleanup().

This isn't the normal behavior as it works for everyone at the moment.
You need to explain what special you are doing here, because of which
you are reaching such a situation.

i.e. you are disabling some code that uses GPU ? Please specify exact
code so others can reproduce it as well.

> Call dev_pm_opp_set_opp() with the recommend OPP in
> panfrost_devfreq_init() to enable the regulator and avoid any switch off
> by regulator_late_cleanup().

The regulator is already enabled I think at this point by the
bootloader. What you are doing here is syncing the state of the
hardware with the software, which would disallow disabling of the
resource unnecessarily.

> Suggested-by: Viresh Kumar <viresh.kumar@...aro.org>
> Signed-off-by: Clément Péron <peron.clem@...il.com>
> ---
>  drivers/gpu/drm/panfrost/panfrost_devfreq.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 5110cd9b2425..67b242407156 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -131,6 +131,14 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>  		return PTR_ERR(opp);
>  
>  	panfrost_devfreq_profile.initial_freq = cur_freq;
> +
> +	/* Setup and enable regulator */

Similarly here, explain why this is required to be done.

> +	ret = dev_pm_opp_set_opp(dev, opp);
> +	if (ret) {
> +		DRM_DEV_ERROR(dev, "Couldn't set recommended OPP\n");
> +		return ret;
> +	}
> +
>  	dev_pm_opp_put(opp);

Do this before checking if (ret), so the resource can be freed all the
time.

>  
>  	/*
> -- 
> 2.34.1

-- 
viresh