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

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Pratyush Yadav <p.yadav@ti.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Kishon Vijay Abraham I <kishon@ti.com>,
	Vinod Koul <vkoul@kernel.org>,
	Peter Ujfalusi <peter.ujfalusi@gmail.com>,
	Maxime Ripard <mripard@kernel.org>,
	Benoit Parrot <bparrot@ti.com>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	Alexandre Courbot <acourbot@chromium.org>,
	Stanimir Varbanov <stanimir.varbanov@linaro.org>,
	Helen Koike <helen.koike@collabora.com>,
	Michael Tretter <m.tretter@pengutronix.de>,
	Peter Chen <peter.chen@nxp.com>,
	Chunfeng Yun <chunfeng.yun@mediatek.com>,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org,
	dmaengine@vger.kernel.org, Vignesh Raghavendra <vigneshr@ti.com>,
	Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Subject: Re: [PATCH 09/16] media: cadence: csi2rx: Turn subdev power on before starting stream
Date: Fri, 2 Apr 2021 13:55:35 +0300	[thread overview]
Message-ID: <YGb4J5q9N0ExOgn9@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20210330173348.30135-10-p.yadav@ti.com>

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@ti.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