Message-ID: <810d566f-af2e-4a19-af39-2abcc558aa6b@ideasonboard.com>
Date: Thu, 20 Nov 2025 15:00:25 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Rishikesh Donadkar <r-donadkar@...com>, jai.luthra@...ux.dev,
 laurent.pinchart@...asonboard.com, mripard@...nel.org
Cc: y-abhilashchandra@...com, devarsht@...com, s-jain1@...com,
 vigneshr@...com, mchehab@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 p.zabel@...gutronix.de, conor+dt@...nel.org, sakari.ailus@...ux.intel.com,
 hverkuil-cisco@...all.nl, jai.luthra@...asonboard.com,
 changhuang.liang@...rfivetech.com, jack.zhu@...rfivetech.com,
 sjoerd@...labora.com, dan.carpenter@...aro.org, hverkuil+cisco@...nel.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v8 07/18] media: cadence: csi2rx: Move to
 .enable/disable_streams API

Hi,

On 12/11/2025 13:54, Rishikesh Donadkar wrote:
> The enable_streams() API in v4l2 supports passing a bitmask to enable
> each pad/stream combination individually on any media subdev. Use this
> API instead of  s_stream() API.
> 
> Implement the enable_stream and disable_stream hooks in place of the
> stream-unaware s_stream hook.
> 
> Remove the lock that was used to serialize stream starts/stops which
> is not required anymore since the v4l2-core serializes the
> enable/disable_streams() calls for the subdev.
> 
> Signed-off-by: Rishikesh Donadkar <r-donadkar@...com>
> ---
>  drivers/media/platform/cadence/cdns-csi2rx.c | 108 +++++++++----------
>  1 file changed, 54 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/media/platform/cadence/cdns-csi2rx.c b/drivers/media/platform/cadence/cdns-csi2rx.c
> index 8c19f125da3e5..34da81893308b 100644
> --- a/drivers/media/platform/cadence/cdns-csi2rx.c
> +++ b/drivers/media/platform/cadence/cdns-csi2rx.c
> @@ -125,12 +125,6 @@ struct csi2rx_priv {
>  	unsigned int			count;
>  	int				error_irq;
>  
> -	/*
> -	 * Used to prevent race conditions between multiple,
> -	 * concurrent calls to start and stop.
> -	 */
> -	struct mutex			lock;
> -
>  	void __iomem			*base;
>  	struct clk			*sys_clk;
>  	struct clk			*p_clk;
> @@ -268,20 +262,21 @@ static int csi2rx_configure_ext_dphy(struct csi2rx_priv *csi2rx)
>  		&csi2rx->source_subdev->entity.pads[csi2rx->source_pad];
>  	union phy_configure_opts opts = { };
>  	struct phy_configure_opts_mipi_dphy *cfg = &opts.mipi_dphy;
> -	struct v4l2_subdev_format sd_fmt = {
> -		.which	= V4L2_SUBDEV_FORMAT_ACTIVE,
> -		.pad	= CSI2RX_PAD_SINK,
> -	};
> +	struct v4l2_subdev_state *state;
> +	struct v4l2_mbus_framefmt *framefmt;
>  	const struct csi2rx_fmt *fmt;
>  	s64 link_freq;
>  	int ret;
>  
> -	ret = v4l2_subdev_call_state_active(&csi2rx->subdev, pad, get_fmt,
> -					    &sd_fmt);
> -	if (ret < 0)
> -		return ret;
> +	state = v4l2_subdev_get_locked_active_state(&csi2rx->subdev);
>  
> -	fmt = csi2rx_get_fmt_by_code(sd_fmt.format.code);
> +	framefmt = v4l2_subdev_state_get_format(state, CSI2RX_PAD_SINK, 0);
> +	if (!framefmt) {
> +		dev_err(csi2rx->dev, "Did not find active sink format\n");
> +		return -EINVAL;
> +	}
> +
> +	fmt = csi2rx_get_fmt_by_code(framefmt->code);
>  
>  	link_freq = v4l2_get_link_freq(src_pad,
>  				       fmt->bpp, 2 * csi2rx->num_lanes);
> @@ -401,16 +396,10 @@ static int csi2rx_start(struct csi2rx_priv *csi2rx)
>  
>  	reset_control_deassert(csi2rx->sys_rst);
>  
> -	ret = v4l2_subdev_call(csi2rx->source_subdev, video, s_stream, true);
> -	if (ret)
> -		goto err_disable_sysclk;
> -
>  	clk_disable_unprepare(csi2rx->p_clk);
>  
>  	return 0;
>  
> -err_disable_sysclk:
> -	clk_disable_unprepare(csi2rx->sys_clk);
>  err_disable_pixclk:
>  	for (; i > 0; i--) {
>  		reset_control_assert(csi2rx->pixel_rst[i - 1]);
> @@ -459,9 +448,6 @@ static void csi2rx_stop(struct csi2rx_priv *csi2rx)
>  	reset_control_assert(csi2rx->p_rst);
>  	clk_disable_unprepare(csi2rx->p_clk);
>  
> -	if (v4l2_subdev_call(csi2rx->source_subdev, video, s_stream, false))
> -		dev_warn(csi2rx->dev, "Couldn't disable our subdev\n");
> -
>  	if (csi2rx->dphy) {
>  		writel(0, csi2rx->base + CSI2RX_DPHY_LANE_CTRL_REG);
>  
> @@ -485,38 +471,56 @@ static int csi2rx_log_status(struct v4l2_subdev *sd)
>  	return 0;
>  }
>  
> -static int csi2rx_s_stream(struct v4l2_subdev *subdev, int enable)
> +static int csi2rx_enable_streams(struct v4l2_subdev *subdev,
> +				 struct v4l2_subdev_state *state, u32 pad,
> +				 u64 streams_mask)
>  {
>  	struct csi2rx_priv *csi2rx = v4l2_subdev_to_csi2rx(subdev);
> -	int ret = 0;
> -
> -	mutex_lock(&csi2rx->lock);
> -
> -	if (enable) {
> -		/*
> -		 * If we're not the first users, there's no need to
> -		 * enable the whole controller.
> -		 */
> -		if (!csi2rx->count) {
> -			ret = csi2rx_start(csi2rx);
> -			if (ret)
> -				goto out;
> -		}
> +	int ret;
>  
> -		csi2rx->count++;
> -	} else {
> -		csi2rx->count--;
> +	/*
> +	 * If we're not the first users, there's no need to
> +	 * enable the whole controller.
> +	 */
> +	if (!csi2rx->count) {
> +		ret = csi2rx_start(csi2rx);
> +		if (ret)
> +			return ret;
> +	}
>  
> -		/*
> -		 * Let the last user turn off the lights.
> -		 */
> +	/* Start streaming on the source */
> +	ret = v4l2_subdev_enable_streams(csi2rx->source_subdev, csi2rx->source_pad,
> +					 BIT(0));

The stream mask is u64, so better use BIT_U64. It doesn't matter here,
but before you know it, you have switched BIT(0) to BIT(foo->bar), and
someone sets bar to 34 and it's broken...

Yes, I see this being changed later, to variable set with BIT_ULL()
(that could be changed to BIT_U64). Nevertheless, better use the correct
macro.

But a bigger issue is if this and patches 6 and 8 are correct or could
be improved.

I think in this one you remove s_stream from cdns-csi2. But the j7
csi2rx is still calling s_stream, so it would fail with this patch. In
patch 8 you switch j7 csi2rx from s_stream to enable_streams. But in
patch 6 you added mutex, locking and s_stream to j7 csi2rx, and in patch
8 you remove that.

Maybe the end result is fine, but it all does feel messy. I think the
patches we should have are:

- Use v4l2_subdev_enable_streams() in j7-csi2rx instead of calling
s_stream. v4l2_subdev_enable_streams() will work with either .s_stream
and .enable_stream in cdns-csi2rx

- Patch 7 (with BIT_64()) to convert cdns-csi2rx

- Patches 6 and 8 combined. You're essentially adding a new subdev, just
do it right from the start with .enable_streams, state, etc., instead of
mutex and s_stream which are removed two patches later.

 Tomi

> +	if (ret) {
> +		dev_err(csi2rx->dev,
> +			"Failed to start streams %d on subdev\n", 0);
>  		if (!csi2rx->count)
>  			csi2rx_stop(csi2rx);
> +		return ret;
>  	}
>  
> -out:
> -	mutex_unlock(&csi2rx->lock);
> -	return ret;
> +	csi2rx->count++;
> +	return 0;
> +}
> +
> +static int csi2rx_disable_streams(struct v4l2_subdev *subdev,
> +				  struct v4l2_subdev_state *state, u32 pad,
> +				  u64 streams_mask)
> +{
> +	struct csi2rx_priv *csi2rx = v4l2_subdev_to_csi2rx(subdev);
> +
> +	if (v4l2_subdev_disable_streams(csi2rx->source_subdev,
> +					csi2rx->source_pad, BIT(0))) {
> +		dev_err(csi2rx->dev, "Couldn't disable our subdev\n");
> +	}
> +
> +	csi2rx->count--;
> +
> +	/* Let the last user turn off the lights. */
> +	if (!csi2rx->count)
> +		csi2rx_stop(csi2rx);
> +
> +	return 0;
>  }
>  
>  static int csi2rx_enum_mbus_code(struct v4l2_subdev *subdev,
> @@ -611,10 +615,8 @@ static const struct v4l2_subdev_pad_ops csi2rx_pad_ops = {
>  	.enum_mbus_code	= csi2rx_enum_mbus_code,
>  	.get_fmt	= v4l2_subdev_get_fmt,
>  	.set_fmt	= csi2rx_set_fmt,
> -};
> -
> -static const struct v4l2_subdev_video_ops csi2rx_video_ops = {
> -	.s_stream	= csi2rx_s_stream,
> +	.enable_streams         = csi2rx_enable_streams,
> +	.disable_streams        = csi2rx_disable_streams,
>  };
>  
>  static const struct v4l2_subdev_core_ops csi2rx_core_ops = {
> @@ -623,7 +625,6 @@ static const struct v4l2_subdev_core_ops csi2rx_core_ops = {
>  
>  static const struct v4l2_subdev_ops csi2rx_subdev_ops = {
>  	.core		= &csi2rx_core_ops,
> -	.video		= &csi2rx_video_ops,
>  	.pad		= &csi2rx_pad_ops,
>  };
>  
> @@ -829,7 +830,6 @@ static int csi2rx_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  	platform_set_drvdata(pdev, csi2rx);
>  	csi2rx->dev = &pdev->dev;
> -	mutex_init(&csi2rx->lock);
>  
>  	ret = csi2rx_get_resources(csi2rx, pdev);
>  	if (ret)

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