linux-kernel - Re: [PATCH v2 4/4] drm/imagination: Skip clocks if platform PM manages resources

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Message-ID: <20250415-poetic-magenta-cicada-9d1ee7@houat>
Date: Tue, 15 Apr 2025 10:55:07 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Michal Wilczynski <m.wilczynski@...sung.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Pavel Machek <pavel@...nel.org>, Drew Fustini <drew@...7.com>, 
	Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Philipp Zabel <p.zabel@...gutronix.de>, 
	Frank Binns <frank.binns@...tec.com>, Matt Coster <matt.coster@...tec.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, m.szyprowski@...sung.com, 
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 4/4] drm/imagination: Skip clocks if platform PM
 manages resources

On Mon, Apr 14, 2025 at 08:52:58PM +0200, Michal Wilczynski wrote:
> Update the Imagination PVR driver to skip clock management during
> initialization if the platform PM has indicated that it manages platform
> resources.
> 
> This is necessary for platforms like the T-HEAD TH1520, where the GPU's
> clocks and resets are managed via a PM domain, and should not be
> manipulated directly by the GPU driver.
> 
> Signed-off-by: Michal Wilczynski <m.wilczynski@...sung.com>
> ---
>  drivers/gpu/drm/imagination/pvr_device.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/imagination/pvr_device.c b/drivers/gpu/drm/imagination/pvr_device.c
> index 1704c0268589bdeb65fa6535f9ec63182b0a3e94..f40468b99cf14da418aeecde086f009695ff877c 100644
> --- a/drivers/gpu/drm/imagination/pvr_device.c
> +++ b/drivers/gpu/drm/imagination/pvr_device.c
> @@ -504,10 +504,16 @@ pvr_device_init(struct pvr_device *pvr_dev)
>  	if (err)
>  		return err;
>  
> -	/* Enable and initialize clocks required for the device to operate. */
> -	err = pvr_device_clk_init(pvr_dev);
> -	if (err)
> -		return err;
> +	/*
> +	 * Only initialize clocks if they are not managed by the platform's
> +	 * PM domain.
> +	 */
> +	if (!device_platform_resources_pm_managed(dev)) {
> +		/* Enable and initialize clocks required for the device to operate. */
> +		err = pvr_device_clk_init(pvr_dev);
> +		if (err)
> +			return err;
> +	}

So, how does that work for devfreq? I can understand the rationale for
resets and the sys clock, but the core clock at least should really be
handled by the driver.

Maxime

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