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Date:   Wed, 14 Sep 2022 13:58:08 +0200
From:   Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
To:     Steve Longerbeam <slongerbeam@gmail.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        linux-media@vger.kernel.org, linux-staging@lists.linux.dev,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        kernel@puri.sm, phone-devel@vger.kernel.org
Subject: [PATCH 1/2] media: imx: Round line size to 4 bytes
Message-ID: <20220914113436.1503790-1-dorota.czaplejewicz@puri.sm>
Organization: Purism
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This has been broken in e352833d, which does not actually copy the logic
from 056f9af9.

Section 13.7.6.13 "CSI Image Parameter Register" of the
i.MX 8M Quad Applications Processors Reference Manual
states that the line size should be divisible by 8 bytes.
However, the hardware also accepts sizes divisible by 4 bytes.

This patch accepts line sizes divisible 4-bytes in non-planar mode.

Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz@puri.sm>
---
Hi,

in recent kernels, I've noticed that the Librem 5 camera driver no longer w=
orks. The s5k3l6xx out of tree sensor driver uses sizes divisible by 4 and =
not by 8, for which I submitted the patch 056f9af9 . The new kernels no lon=
ger accept sizes divisible by 4.

I tracked down the source: previously, the video device on the imx8m used i=
mx_media_mbus_fmt_to_pix_fmt. e352833d introduced imx7_csi_mbus_fmt_to_pix_=
fmt, which is what is used now exclusively. However, imx7_csi_mbus_fmt_to_p=
ix_fmt *does not* contain the same logic, and does not provide an explanati=
on why the logic is different.

I don't know why the "imx_*" is not used any more on the i.MX8M SoC, but I =
presume that "imx7_*" is the correct code path. That indicates that "imx_*"=
 is *not* the correct code for this SoC.

Under those assumptions, I added the relaxed rounding to the "imx7_*" funct=
ion, to match what the SoC can do (patch 1). I also reverted my original pa=
tch (patch 2), because if "imx7_*" is the correct function for my SoC, then=
 I had never intended to mess with whatever other SoC is handled by the "im=
x_" function.

Cheers,
Dorota

 drivers/staging/media/imx/imx7-media-csi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/imx/imx7-media-csi.c b/drivers/staging/m=
edia/imx/imx7-media-csi.c
index 643547bfa90f..bafbb5ef08d5 100644
--- a/drivers/staging/media/imx/imx7-media-csi.c
+++ b/drivers/staging/media/imx/imx7-media-csi.c
@@ -1000,10 +1000,10 @@ static int imx7_csi_mbus_fmt_to_pix_fmt(struct v4l2=
_pix_format *pix,
 	}
=20
 	/* Round up width for minimum burst size */
-	width =3D round_up(mbus->width, 8);
+	width =3D round_up(mbus->width, 4);
=20
 	/* Round up stride for IDMAC line start address alignment */
-	stride =3D round_up((width * cc->bpp) >> 3, 8);
+	stride =3D round_up((width * cc->bpp) >> 3, 4);
=20
 	pix->width =3D width;
 	pix->height =3D mbus->height;
--=20
2.37.3


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