linux-kernel - Re: [PATCH] media: imx: Fix rounding

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Date:   Fri, 24 Sep 2021 13:46:15 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Dorota Czaplejewicz <dorota.czaplejewicz@...i.sm>
Cc:     Steve Longerbeam <slongerbeam@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...i.sm, phone-devel@...r.kernel.org
Subject: Re: [PATCH] media: imx: Fix rounding

Hi Dorota,

On Fri, Sep 24, 2021 at 12:06:31PM +0200, Dorota Czaplejewicz wrote:
> Change rounding to the minimal burst size from 2^n to n.
> 
> This fixes images with sizes that are a multiple of 8 pixels.

Could you elaborate on what is currently wrong with images that are a
multiple of 8 pixels wide? Or are you rather trying to add support
for images that are not a multiple of 8 pixels wide?

> 
> See section 13.7.6.13 CSI Image Parameter Register of the
> i.MX 8M Quad Applications Processors Reference Manual.
> 
> Fixes: 451a7b7815d0b ("media: imx: lift CSI and PRP ENC/VF width
> alignment restriction")
> Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@...i.sm>
> ---
> Hi,
> 
> I tested this patch on the Librem 5 with the main camera.
> 
> --Dorota
>  drivers/staging/media/imx/imx-media-utils.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/media/imx/imx-media-utils.c b/drivers/staging/media/imx/imx-media-utils.c
> index 5128915a5d6f..a2d8fab32a39 100644
> --- a/drivers/staging/media/imx/imx-media-utils.c
> +++ b/drivers/staging/media/imx/imx-media-utils.c
> @@ -545,13 +545,13 @@ int imx_media_mbus_fmt_to_pix_fmt(struct v4l2_pix_format *pix,
>  	}
>  
>  	/* Round up width for minimum burst size */
> -	width = round_up(mbus->width, 8);
> +	width = round_up(mbus->width, 3);

That is not a valid use of the round_up() macro anymore.
The second parameter must be a power of 2.

regards
Philipp