linux-kernel - Re: [PATCH v2 09/10] drm/panthor: devfreq: add pluggable devfreq providers

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Message-ID: <CAPaKu7TEN++z8r68k_4-iCyMLMthqJBUX35pgXupAHPdfttrYg@mail.gmail.com>
Date: Fri, 12 Sep 2025 15:53:50 -0700
From: Chia-I Wu <olvaffe@...il.com>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Boris Brezillon <boris.brezillon@...labora.com>, Steven Price <steven.price@....com>, 
	Liviu Dudau <liviu.dudau@....com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Matthias Brugger <matthias.bgg@...il.com>, MyungJoo Ham <myungjoo.ham@...sung.com>, 
	Kyungmin Park <kyungmin.park@...sung.com>, Chanwoo Choi <cw00.choi@...sung.com>, 
	Jassi Brar <jassisinghbrar@...il.com>, Kees Cook <kees@...nel.org>, 
	"Gustavo A. R. Silva" <gustavoars@...nel.org>, Chen-Yu Tsai <wenst@...omium.org>, kernel@...labora.com, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-mediatek@...ts.infradead.org, linux-pm@...r.kernel.org, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 09/10] drm/panthor: devfreq: add pluggable devfreq providers

On Fri, Sep 12, 2025 at 11:38 AM Nicolas Frattaroli
<nicolas.frattaroli@...labora.com> wrote:
<snipped>
> diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.h b/drivers/gpu/drm/panthor/panthor_devfreq.h
> index a891cb5fdc34636444f141e10f5d45828fc35b51..94c9768d5d038c4ba8516929edb565a1f13443fb 100644
> --- a/drivers/gpu/drm/panthor/panthor_devfreq.h
> +++ b/drivers/gpu/drm/panthor/panthor_devfreq.h
> @@ -8,6 +8,7 @@
>
>  struct devfreq;
>  struct thermal_cooling_device;
> +struct platform_device;
>
>  struct panthor_device;
>
> @@ -43,6 +44,19 @@ struct panthor_devfreq {
>         spinlock_t lock;
>  };
>
> +struct panthor_devfreq_provider {
> +       /** @dev: device pointer to the provider device */
> +       struct device *dev;
> +       /**
> +        * @init: the provider's init callback that allocates a
> +        * &struct panthor_devfreq, adds it to panthor, and adds a devfreq
> +        * device to panthor. Will be called during panthor's probe.
> +        */
> +       int (*init)(struct panthor_device *ptdev, struct device *dev);
> +
> +       struct list_head node;
> +};
On mt8196, we have performance-domains to replace several other
properties: clocks, *-supply, power-domains, operating-points-v2.
There are also quirks, such as GPU_SHADER_PRESENT should be masked by
GF_REG_SHADER_PRESENT. It feels like that the scope of
panthor_devfreq_provider is more broader, and at least the naming is
not right.

Another issue is I am not sure if we need to expose panthor_device
internals to the provider. mtk_mfg accesses very few fields of
panthor_device. It seems we can make the two less coupled.

I might change my view as mtk_mfg evolves and requires tigher
integration with panthor. But as is, I might prefer for mtk_mfg to
live under drivers/soc/mediatek and provide a header for panthor to
use in soc-specific path.


> +
>
>  int panthor_devfreq_init(struct panthor_device *ptdev);
>
> @@ -57,4 +71,6 @@ int panthor_devfreq_get_dev_status(struct device *dev,
>
>  unsigned long panthor_devfreq_get_freq(struct panthor_device *ptdev);
>
> +int panthor_devfreq_register_provider(struct panthor_devfreq_provider *prov);
> +
>  #endif /* __PANTHOR_DEVFREQ_H__ */
>
> --
> 2.51.0
>