linux-kernel - Re: [PATCH 09/16] media: cadence: csi2rx: Turn subdev power on before starting stream

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Message-ID: <YGb4J5q9N0ExOgn9@pendragon.ideasonboard.com>
Date:   Fri, 2 Apr 2021 13:55:35 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Pratyush Yadav <p.yadav@...com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Maxime Ripard <mripard@...nel.org>,
        Benoit Parrot <bparrot@...com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Alexandre Courbot <acourbot@...omium.org>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Helen Koike <helen.koike@...labora.com>,
        Michael Tretter <m.tretter@...gutronix.de>,
        Peter Chen <peter.chen@....com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
        dmaengine@...r.kernel.org, Vignesh Raghavendra <vigneshr@...com>,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: Re: [PATCH 09/16] media: cadence: csi2rx: Turn subdev power on
 before starting stream

Hi Pratyush,

Thank you for the patch.

On Tue, Mar 30, 2021 at 11:03:41PM +0530, Pratyush Yadav wrote:
> The subdevice power needs to be turned on before the stream is started.
> Otherwise it might not be in the proper state to stream the data. Turn
> it off when stopping the stream.

The .s_power() operation is deprecated. Subdev drivers should control
power internally in their .s_stream() operation, and they should use
runtime PM to do so (this will allow usage of runtime PM autosuspend, to
avoid expensive power off/on cycles when stopping and restarting video
capture).

> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> ---
>  drivers/media/platform/cadence/cdns-csi2rx.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/media/platform/cadence/cdns-csi2rx.c b/drivers/media/platform/cadence/cdns-csi2rx.c
> index 7d1ac51e0698..3385e1bc213e 100644
> --- a/drivers/media/platform/cadence/cdns-csi2rx.c
> +++ b/drivers/media/platform/cadence/cdns-csi2rx.c
> @@ -256,6 +256,10 @@ static int csi2rx_start(struct csi2rx_priv *csi2rx)
>  
>  	writel(reg, csi2rx->base + CSI2RX_STATIC_CFG_REG);
>  
> +	ret = v4l2_subdev_call(csi2rx->source_subdev, core, s_power, true);
> +	if (ret && ret != -ENOIOCTLCMD)
> +		goto err_disable_pclk;
> +
>  	ret = v4l2_subdev_call(csi2rx->source_subdev, video, s_stream, true);
>  	if (ret)
>  		goto err_disable_pclk;
> @@ -358,6 +362,10 @@ static void csi2rx_stop(struct csi2rx_priv *csi2rx)
>  	if (v4l2_subdev_call(csi2rx->source_subdev, video, s_stream, false))
>  		dev_warn(csi2rx->dev, "Couldn't disable our subdev\n");
>  
> +	ret = v4l2_subdev_call(csi2rx->source_subdev, core, s_power, false);
> +	if (ret && ret != -ENOIOCTLCMD)
> +		dev_warn(csi2rx->dev, "Couldn't power off subdev\n");
> +
>  	if (csi2rx->dphy) {
>  		writel(0, csi2rx->base + CSI2RX_DPHY_LANE_CTRL_REG);
>  

-- 
Regards,

Laurent Pinchart