linux-kernel - Re: [PATCH v3 07/15] media: rcar-csi2: Optimize rcsi2_calc

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Message-ID: <20250602094357.GH3645@pendragon.ideasonboard.com>
Date: Mon, 2 Jun 2025 12:43:57 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
Cc: Niklas Söderlund <niklas.soderlund@...natech.se>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Niklas Söderlund <niklas.soderlund+renesas@...natech.se>,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Jacopo Mondi <jacopo.mondi@...asonboard.com>
Subject: Re: [PATCH v3 07/15] media: rcar-csi2: Optimize rcsi2_calc_mbps()

Hi Tomi,

Thank you for the patch.

On Fri, May 30, 2025 at 04:50:36PM +0300, Tomi Valkeinen wrote:
> With modern drivers supporting link-freq, we don't need to do any
> calculations based on the bpp and number of lanes when figuring out the
> link frequency. However, the code currently always runs code to get the
> bpp and number of lanes.
> 
> Optimize the rcsi2_calc_mbps() so that we only do that when needed, i.e.
> when querying the link-freq is not supported by the upstream subdevice.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
> ---
>  drivers/media/platform/renesas/rcar-csi2.c | 50 +++++++++++++++++-------------
>  1 file changed, 29 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/media/platform/renesas/rcar-csi2.c b/drivers/media/platform/renesas/rcar-csi2.c
> index 90973f3cba38..e0a0fd96459b 100644
> --- a/drivers/media/platform/renesas/rcar-csi2.c
> +++ b/drivers/media/platform/renesas/rcar-csi2.c
> @@ -1001,15 +1001,10 @@ static int rcsi2_get_active_lanes(struct rcar_csi2 *priv,
>  static int rcsi2_calc_mbps(struct rcar_csi2 *priv,
>  			   struct v4l2_subdev_state *state)
>  {
> -	const struct rcar_csi2_format *format;
> -	struct v4l2_mbus_framefmt *fmt;
>  	struct media_pad *remote_pad;
>  	struct v4l2_subdev *source;
> -	unsigned int lanes;
> -	unsigned int bpp;
>  	s64 freq;
>  	u64 mbps;
> -	int ret;
>  
>  	if (!priv->remote)
>  		return -ENODEV;
> @@ -1017,28 +1012,41 @@ static int rcsi2_calc_mbps(struct rcar_csi2 *priv,
>  	source = priv->remote;
>  	remote_pad = &source->entity.pads[priv->remote_pad];
>  
> -	ret = rcsi2_get_active_lanes(priv, &lanes);
> -	if (ret)
> -		return ret;
> +	/*
> +	 * First try to get the real link freq. If that fails, try the heuristic
> +	 * method with bpp and lanes (but that only works for one route).
> +	 */
> +	freq = v4l2_get_link_freq(remote_pad, 0, 0);
> +	if (freq < 0) {
> +		const struct rcar_csi2_format *format;
> +		struct v4l2_mbus_framefmt *fmt;

This can be const.

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

> +		unsigned int lanes;
> +		unsigned int bpp;
> +		int ret;
>  
> -	fmt = v4l2_subdev_state_get_format(state, RCAR_CSI2_SINK);
> -	if (!fmt)
> -		return -EINVAL;
> +		ret = rcsi2_get_active_lanes(priv, &lanes);
> +		if (ret)
> +			return ret;
>  
> -	format = rcsi2_code_to_fmt(fmt->code);
> -	if (!format)
> -		return -EINVAL;
> +		fmt = v4l2_subdev_state_get_format(state, RCAR_CSI2_SINK);
> +		if (!fmt)
> +			return -EINVAL;
>  
> -	bpp = format->bpp;
> +		format = rcsi2_code_to_fmt(fmt->code);
> +		if (!format)
> +			return -EINVAL;
>  
> -	freq = v4l2_get_link_freq(remote_pad, bpp, 2 * lanes);
> -	if (freq < 0) {
> -		int ret = (int)freq;
> +		bpp = format->bpp;
>  
> -		dev_err(priv->dev, "failed to get link freq for %s: %d\n",
> -			source->name, ret);
> +		freq = v4l2_get_link_freq(remote_pad, bpp, 2 * lanes);
> +		if (freq < 0) {
> +			int ret = (int)freq;
>  
> -		return ret;
> +			dev_err(priv->dev, "failed to get link freq for %s: %d\n",
> +				source->name, ret);
> +
> +			return ret;
> +		}
>  	}
>  
>  	mbps = div_u64(freq * 2, MEGA);

-- 
Regards,

Laurent Pinchart