Re: [RFC PATCH 2/3] media: imx: imx7-media-csi: Set TWO_8BIT_SENSOR for >= 10-bit formats

[Frieder Schrempf <frieder.schrempf@kontron.de>]

Hi Laurent,

On 19.05.21 02:16, Laurent Pinchart wrote:
> Hi Frieder,
> 
> On Mon, May 17, 2021 at 12:21:17PM +0200, Frieder Schrempf wrote:
>> On 16.05.21 04:42, Laurent Pinchart wrote:
>>> Sample code from NXP, as well as experiments on i.MX8MM with RAW10
>>> capture with an OV5640 sensor connected over CSI-2, showed that the
>>> TWO_8BIT_SENSOR field of the CSICR3 register needs to be set for formats
>>> larger than 8 bits. Do so, even if the reference manual doesn't clearly
>>> describe the effect of the field.
>>>
>>> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>
>> For the ADV7280-M I also have the diffs below applied. Do you think
>> setting BIT_MIPI_DOUBLE_CMPNT is specific to MEDIA_BUS_FMT_UYVY8_2X8?
> 
> Do you need MEDIA_BUS_FMT_UYVY8_2X8 ? Neither MEDIA_BUS_FMT_UYVY8_1X16
> nor MEDIA_BUS_FMT_UYVY8_2X8 match exactly how YUV 4:2:2 data is
> transmitted over CSI-2. V4L2 uses MEDIA_BUS_FMT_UYVY8_1X16 as a
> convention.

I just use MEDIA_BUS_FMT_UYVY8_2X8 as the ADV7280 driver sets it. But if the convention is to use MEDIA_BUS_FMT_UYVY8_1X16 for YUV422, then maybe the ADV driver needs to be fixed.

> 
>> In the RM it mentions YUV422 in the description of
>> BIT_MIPI_DOUBLE_CMPNT and without setting it, the colors are all
>> wrong.
> 
> That's interesting. I've tested YUV 4:2:2 with an OV5640 sensor, and I
> don't recall having to set the MIPI_DOUBLE_CMPNT field. I'll try to
> retest.
> 
>> I know this is not really related to this patch. I'm just wondering
>> how to properly support my setup.
> 
> It's hard to tell :-( The MIPI_CSI2_ISP_CONFIG PIXEL_MODE and PARALLEL
> fields are not well documented, and neither is the CSI_CR18
> MIPI_DOUBLE_CMPNT field. While the CSIS and the CSI bridge are
> documented, how they're integrated isn't described. So far, I can only
> guess.
> 
>> --- a/drivers/staging/media/imx/imx7-mipi-csis.c
>> +++ b/drivers/staging/media/imx/imx7-mipi-csis.c
>> @@ -346,6 +346,11 @@ struct csis_pix_format {
>>  
>>  static const struct csis_pix_format mipi_csis_formats[] = {
>>         /* YUV formats. */
>> +       {
>> +               .code = MEDIA_BUS_FMT_UYVY8_2X8,
>> +               .data_type = MIPI_CSI2_DATA_TYPE_YUV422_8,
>> +               .width = 8,
>> +       },
>>         {
>>                 .code = MEDIA_BUS_FMT_UYVY8_1X16,
>>                 .data_type = MIPI_CSI2_DATA_TYPE_YUV422_8,
>>
>> --- a/drivers/staging/media/imx/imx7-mipi-csis.c
>> +++ b/drivers/staging/media/imx/imx7-mipi-csis.c
>> @@ -504,7 +504,7 @@ static void __mipi_csis_set_format(struct csi_state *state)
>>         /* Color format */
>>         val = mipi_csis_read(state, MIPI_CSIS_ISP_CONFIG_CH(0));
>>         val &= ~(MIPI_CSIS_ISPCFG_ALIGN_32BIT | MIPI_CSIS_ISPCFG_FMT_MASK);
>> -       val |= MIPI_CSIS_ISPCFG_FMT(state->csis_fmt->data_type);
>> +       val |= MIPI_CSIS_ISPCFG_FMT(state->csis_fmt->data_type) | MIPI_CSIS_ISPCFG_PIXEL_MODE_DUAL;
>>         mipi_csis_write(state, MIPI_CSIS_ISP_CONFIG_CH(0), val);
>>  
>>         /* Pixel resolution */
>>
>> --- a/drivers/staging/media/imx/imx7-media-csi.c
>> +++ b/drivers/staging/media/imx/imx7-media-csi.c
>> @@ -492,7 +492,8 @@ static void imx7_csi_configure(struct imx7_csi *csi)
>>                 case MEDIA_BUS_FMT_UYVY8_1X16:
>>                 case MEDIA_BUS_FMT_YUYV8_2X8:
>>                 case MEDIA_BUS_FMT_YUYV8_1X16:
>> -                       cr18 |= BIT_MIPI_DATA_FORMAT_YUV422_8B;
>> +                       cr3 |= BIT_TWO_8BIT_SENSOR;
>> +                       cr18 |= BIT_MIPI_DATA_FORMAT_YUV422_8B | BIT_MIPI_DOUBLE_CMPNT;
> 
> I notice that you set both PIXEL_MODE_DUAL and MIPI_DOUBLE_CMPNT. Have
> you tried setting neither ?

Yes, but as soon as I don't set PIXEL_MODE_DUAL, I get overflow errors from the MIPI CSI2 controller and it doesn't work at all.

> 
> Have you also tried using MEDIA_BUS_FMT_UYVY8_1X16 ? The difference
> between MEDIA_BUS_FMT_UYVY8_2X8 and MEDIA_BUS_FMT_UYVY8_1X16 in this
> driver is the width value passed to v4l2_get_link_freq(). With
> MEDIA_BUS_FMT_UYVY8_2X8 you'll end up with a computed link frequency
> equal to half of the actual value, and thus a wrong Ths_settle value. It
> shuold have no other influence though.

The link frequency calculation doesn't work for me at the moment, as the ADV driver doesn't provide any of the controls V4L2_CID_LINK_FREQ or V4L2_CID_PIXEL_RATE. So for now I just hardcoded the Ths_settle value.

Thanks for your efforts!
Frieder