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

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Date: Mon, 15 Apr 2024 10:38:42 -0600
From: Luis Garcia <git@...gi311.com>
To: Alexander Stein <alexander.stein@...tq-group.com>,
 linux-media@...r.kernel.org
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
Subject: Re: [PATCH v4 02/25] media: i2c: imx258: Make image geometry meet
 sensor requirements

On 4/15/24 00:25, Alexander Stein wrote:
> 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
>


I assume this is what you are looking for
https://photos.luigi311.com/share/Imk6odsR_44VYsRvfmRwBVoG1TMnXtI61PP4sjssbmKAcNEYuVPRa9W-vIU7rpa-Ask

 
> 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
> 

Flipping defaults are changed around looks like based on use cases. Patch 20
is what actually brings in flipping and brings in the 4 definitions like you
are expecting

+	/* 10-bit modes. */
+	MEDIA_BUS_FMT_SRGGB10_1X10,
+	MEDIA_BUS_FMT_SGRBG10_1X10,
+	MEDIA_BUS_FMT_SGBRG10_1X10,
+	MEDIA_BUS_FMT_SBGGR10_1X10