Re: [PATCH v2 1/3] media: imx: imx7-media-csi: Get rid of superfluous call to imx7_csi_mbus_fmt_to_pix_fmt

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Alexander Stein <alexander.stein@ew.tq-group.com>
Cc: Rui Miguel Silva <rmfrfs@gmail.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	NXP Linux Team <linux-imx@nxp.com>,
	linux-media@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/3] media: imx: imx7-media-csi: Get rid of superfluous call to imx7_csi_mbus_fmt_to_pix_fmt
Date: Tue, 18 Apr 2023 12:27:13 +0300	[thread overview]
Message-ID: <20230418092713.GA26319@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20230418071439.197735-2-alexander.stein@ew.tq-group.com>

Hi Alexander,

Thank you for the patch.

On Tue, Apr 18, 2023 at 09:14:37AM +0200, Alexander Stein wrote:
> There is no need to convert input pixformat to mbus_framefmt and back
> again. Instead apply pixformat width contrains directly.
> 
> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> ---
>  drivers/media/platform/nxp/imx7-media-csi.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/platform/nxp/imx7-media-csi.c b/drivers/media/platform/nxp/imx7-media-csi.c
> index b701e823436a8..bd649fd9166fd 100644
> --- a/drivers/media/platform/nxp/imx7-media-csi.c
> +++ b/drivers/media/platform/nxp/imx7-media-csi.c
> @@ -1145,8 +1145,8 @@ static const struct imx7_csi_pixfmt *
>  __imx7_csi_video_try_fmt(struct v4l2_pix_format *pixfmt,
>  			 struct v4l2_rect *compose)
>  {
> -	struct v4l2_mbus_framefmt fmt_src;
>  	const struct imx7_csi_pixfmt *cc;
> +	u32 stride;
>  
>  	/*
>  	 * Find the pixel format, default to the first supported format if not
> @@ -1172,12 +1172,16 @@ __imx7_csi_video_try_fmt(struct v4l2_pix_format *pixfmt,
>  		}
>  	}
>  
> -	v4l2_fill_mbus_format(&fmt_src, pixfmt, 0);
> -	imx7_csi_mbus_fmt_to_pix_fmt(pixfmt, &fmt_src, cc);

Could you please keep the comment from imx7_csi_mbus_fmt_to_pix_fmt()
here, to indicate where the alignment comes from ?

	/* Round up width for minimum burst size */

We should likely revisit this in the future, I don't think the alignment
is actually needed. This could be recorded already:

	/*
	 * Round up width for minimum burst size.
	 *
	 * TODO: Implement configurable stride support, and check what the real
	 * hardware alignment constraint on the width is.
	 */

> +	v4l_bound_align_image(&pixfmt->width, 1, 0xffff, 8,
> +			      &pixfmt->height, 1, 0xffff, 1, 0);
> +
> +	stride = round_up((pixfmt->width * cc->bpp) / 8, 8);

You can drop the round_up(), as pixfmt->width is now a multiple of 8, so

	pixfmt->bytesperline = pixfmt->width * cc->bpp / 8;

> +	pixfmt->bytesperline = stride;
> +	pixfmt->sizeimage = stride * pixfmt->height;
>  
>  	if (compose) {
> -		compose->width = fmt_src.width;
> -		compose->height = fmt_src.height;
> +		compose->width = pixfmt->width;

This is a change of behaviour, compose->width used to be set to the
unaligned width.

> +		compose->height = pixfmt->height;
>  	}
>  
>  	return cc;

-- 
Regards,

Laurent Pinchart

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