linux-kernel - Re: [PATCH v4 02/25] media: i2c: imx258: Make image geometry meet sensor requirements

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Message-ID: <6041186.lOV4Wx5bFT@steina-w>
Date: Mon, 15 Apr 2024 08:25:02 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: linux-media@...r.kernel.org, git@...gi311.com
Cc: dave.stevenson@...pberrypi.com, jacopo.mondi@...asonboard.com, mchehab@...nel.org, robh@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com, sakari.ailus@...ux.intel.com, devicetree@...r.kernel.org, imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, pavel@....cz, phone-devel@...r.kernel.org, Luis Garcia <git@...gi311.com>
Subject: Re: [PATCH v4 02/25] media: i2c: imx258: Make image geometry meet sensor requirements

Hi,

Am Sonntag, 14. April 2024, 22:34:40 CEST schrieb git@...gi311.com:
> From: Dave Stevenson <dave.stevenson@...pberrypi.com>
> 
> The output image is defined as being 4208x3118 pixels in size.
> Y_ADD_STA register was set to 0, and Y_ADD_END to 3118, giving
> 3119 lines total.
> 
> The datasheet lists a requirement for Y_ADD_STA to be a multiple
> of a power of 2 depending on binning/scaling mode (2 for full pixel,
> 4 for x2-bin/scale, 8 for (x2-bin)+(x2-subsample) or x4-bin, or 16
> for (x4-bin)+(x2-subsample)).
> (Y_ADD_END – Y_ADD_STA + 1) also has to be a similar power of 2.
> 
> The current configuration for the full res modes breaks that second
> requirement, and we can't increase Y_ADD_STA to 1 to retain exactly
> the same field of view as that then breaks the first requirement.
> For the binned modes, they are worse off as 3118 is not a multiple of
> 4.
> 
> Increase the main mode to 4208x3120 so that it is the same FOV as the
> binned modes, with Y_ADD_STA at 0.
> Fix Y_ADD_STA and Y_ADD_END for the binned modes so that they meet the
> sensor requirements.
> 
> This does change the Bayer order as the default configuration is for
> H&V flips to be enabled, so readout is from Y_STA_END to Y_ADD_STA,
> and this patch has changed Y_STA_END.
> 
> Signed-off-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
> Reviewed-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>
> Signed-off-by: Luis Garcia <git@...gi311.com>
> Reviewed-by: Pavel Machek <pavel@....cz>
> ---
>  drivers/media/i2c/imx258.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/media/i2c/imx258.c b/drivers/media/i2c/imx258.c
> index 2dbafd21dd70..4a7048d834c6 100644
> --- a/drivers/media/i2c/imx258.c
> +++ b/drivers/media/i2c/imx258.c
> [snip]
> @@ -707,7 +707,7 @@ static int imx258_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
>  	/* Initialize try_fmt */
>  	try_fmt->width = supported_modes[0].width;
>  	try_fmt->height = supported_modes[0].height;
> -	try_fmt->code = MEDIA_BUS_FMT_SGRBG10_1X10;
> +	try_fmt->code = MEDIA_BUS_FMT_SBGGR10_1X10;

Does someone have access to the data sheet? I am wondering how the
arrangement of the pixel array is shown. I've the following (identical)
array for these sensors:
* imx290/imx327
* imx219
* imx415

G B G B
R G R G
G B G B
R G R G

Yet each driver configures a different bus format:

* imx290.c: MEDIA_BUS_FMT_SRGGB10_1X10
* imx415.c: MEDIA_BUS_FMT_SGBRG10_1X10
* imx219.c: MEDIA_BUS_FMT_SRGGB10_1X10 (no flip)

imx219 actually defines all 4 10 Bit Bayer patterns and the comment
indicates this depends on how v or h flip is configured.
Reading the commit message apparently the same is true for this driver.

Still this is confusing as I would have expected flipping to be disabled by
default, expecting the same Bayer pattern order for all drivers. Can someone
shed some light?

Best regards,
Alexander

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