linux-kernel - Re: [PATCH v1 00/55] media: Add a helper for obtaining the clock producer

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Message-ID: <CA+V-a8s1wNrgxKJv2KGq_dLXRW2o4Q30TND=0mQs1jG1t7rS+g@mail.gmail.com>
Date: Tue, 24 Jun 2025 21:34:24 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Mehdi Djait <mehdi.djait@...ux.intel.com>
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Subject: Re: [PATCH v1 00/55] media: Add a helper for obtaining the clock producer

On Thu, Jun 19, 2025 at 7:00 PM Mehdi Djait <mehdi.djait@...ux.intel.com> wrote:
>
> Hello everyone,
>
> Here is my v1 for the new helper v4l2_devm_sensor_clk_get()
>
> Any testing of the patches is GREATLY APPRECIATED! Especially the two
> drivers with the special ACPI case:
> 1) OV8865
> 2) OV2680
>
>
> Background
> ----------
>
> A reference to the clock producer is not available to the kernel
> in ACPI-based platforms but the sensor drivers still need them.
>
> devm_clk_get() will return an error and the probe function will fail.
>
>
> Solution
> --------
>
> Introduce a generic helper for v4l2 sensor drivers on both DT- and ACPI-based
> platforms.
>
> This helper behaves the same as clk_get_optional() except where there is
> no clock producer like in ACPI-based platforms.
>
> For ACPI-based platforms the function will read the "clock-frequency"
> ACPI _DSD property and register a fixed frequency clock with the frequency
> indicated in the property.
>
>
> Solution for special ACPI case
> ------------------------------
>
> This function also handles the special ACPI-based system case where:
>
> 1) The clock-frequency _DSD property is present.
> 2) A reference to the clock producer is present, where the clock is provided
> by a camera sensor PMIC driver (e.g. int3472/tps68470.c)
>
> In this case try to set the clock-frequency value to the provided clock.
>
>
> RFC History
> -----------
>
> RFC v4 -> RFC v5:
> Suggested by Arnd Bergmann:
>         - removed IS_REACHABLE(CONFIG_COMMON_CLK). IS_REACHABLE() is actually
>         discouraged [1]. COFIG_COMMON_CLK is a bool, so IS_ENABLED() will be the
>         right solution here
> Suggested by Hans de Goede:
>         - added handling for the special ACPI-based system case, where
>           both a reference to the clock-provider and the _DSD
>           clock-frequency are present.
>         - updated the function's kernel-doc and the commit msg
>           to mention this special case.
> Link RFC v4: https://lore.kernel.org/linux-media/20250321130329.342236-1-mehdi.djait@linux.intel.com/
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/Documentation/kbuild/kconfig-language.rst?h=next-20250513&id=700bd25bd4f47a0f4e02e0a25dde05f1a6b16eea
>
> RFC v3 -> RFC v4:
> Suggested by Laurent:
>         - removed the #ifdef to use IS_REACHABLE(CONFIG_COMMON_CLK)
>         - changed to kasprintf() to allocate the clk name when id is NULL and
>           used the __free(kfree) scope-based cleanup helper when
>           defining the variable to hold the allocated name
> Link v3: https://lore.kernel.org/linux-media/20250321093814.18159-1-mehdi.djait@linux.intel.com/
>
> RFC v2 -> RFC v3:
> - Added #ifdef CONFIG_COMMON_CLK for the ACPI case
> Link v2: https://lore.kernel.org/linux-media/20250310122305.209534-1-mehdi.djait@linux.intel.com/
>
> RFC v1 -> RFC v2:
> Suggested by Sakari:
>     - removed clk_name
>     - removed the IS_ERR() check
>     - improved the kernel-doc comment and commit msg
> Link v1: https://lore.kernel.org/linux-media/20250227092643.113939-1-mehdi.djait@linux.intel.com
>
> Mehdi Djait (55):
>   media: v4l2-common: Add a helper for obtaining the clock producer
>   Documentation: media: camera-sensor: Mention
>     v4l2_devm_sensor_clk_get() for obtaining the clock
>   media: i2c: imx219: Use the v4l2 helper for obtaining the clock
>   media: i2c: mt9p031: Use the v4l2 helper for obtaining the clock
>   media: i2c: ov2659: Use the v4l2 helper for obtaining the clock
>   media: i2c: ov2685: Use the v4l2 helper for obtaining the clock
>   media: i2c: ov5640: Use the v4l2 helper for obtaining the clock
>   media: i2c: ov5645: Use the v4l2 helper for obtaining the clock

For all the above,

Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

Cheers,
Prabhakar