linux-kernel - Re: [PATCH v3 6/9] media: i2c: ov5645: Use runtime PM

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Date:   Thu, 27 Oct 2022 09:22:26 +0000
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Prabhakar <prabhakar.csengg@...il.com>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Shawn Tu <shawnx.tu@...el.com>,
        Jacopo Mondi <jacopo@...ndi.org>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org,
        Biju Das <biju.das.jz@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v3 6/9] media: i2c: ov5645: Use runtime PM

Hi Prabhakar,

Thanks for the update.

On Wed, Oct 26, 2022 at 02:06:55PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> Switch to using runtime PM for power management.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> ---
> v2->v3
> * Jumped to err_pm_runtime label in case of sd register failure
> * Now calling pm_runtime_mark_last_busy() before pm_runtime_put_autosuspend()
>   call
> * Now calling pm_runtime_put_sync() in case s_stream(1) fails
> * In s_stream(0) no calling pm_runtime_mark_last_busy() and
>   pm_runtime_put_autosuspend()
> * Included RB tag from Laurent.
> 
> v1->v2
> * Moved pm_runtime_*_autosuspend() calls after registering the subdev.
> ---
>  drivers/media/i2c/Kconfig  |   2 +-
>  drivers/media/i2c/ov5645.c | 141 +++++++++++++++++++------------------
>  2 files changed, 73 insertions(+), 70 deletions(-)
> 
> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
> index 7806d4b81716..c0edd1017fe8 100644
> --- a/drivers/media/i2c/Kconfig
> +++ b/drivers/media/i2c/Kconfig
> @@ -459,7 +459,7 @@ config VIDEO_OV5640
>  config VIDEO_OV5645
>  	tristate "OmniVision OV5645 sensor support"
>  	depends on OF
> -	depends on I2C && VIDEO_DEV
> +	depends on I2C && PM && VIDEO_DEV

I think you can drop the PM dependency --- the driver will work fine
without CONFIG_PM.

Although one could question why do we have CONFIG_PM. Some systems won't
boot without it and who would want to consume more power than necessary?

Could this be removed altogether? Or perhaps we could add CONFIG_PM
dependency to V4L2 and DVB? :-)

Certainly out of scope of this set though.

-- 
Kind regards,

Sakari Ailus