i.MX8MQ CSI line size constraint - documentation mistake?

[dcz]

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.

I've been using them with a sensor returning 780-byte lines (8bpp), which is divisible by 4, but *not* by 8. This works as long as the total buffer length is divisible by 8 bytes.

I want to add this functionality to the upstream Linux CSI driver, but I'd like to get an opinion from NXP.

Is this supported behaviour, and the datasheet is too strict? Or am I inviting some kind of trouble?

Is the CSI IP used in i.MX7 series working the same way?

[Sanket_Parekh]

Hi @dcz 

I hope you are doing well.

You can set divisible by 4 option, But for that you need to configure input data from the sensor is 10-bit/pixel or 16-bit/pixel format. Please find the reference from below.

Thanks & Regards

Sanket Parekh

[Sanket_Parekh]

Hi @dcz 

I hope you are doing well.

You can set divisible by 4 option, But for that you need to configure input data from the sensor is 10-bit/pixel or 16-bit/pixel format. Please find the reference from below.

Thanks & Regards

Sanket Parekh

[dcz]

Hello Sanket,

I understand that the datasheet says I "should" use line sizes divisible by 4 pixels in 10-bit or 16-bit (so divisible by 8 bytes).

What the datasheet doesn't explicitly say is that I can also use line sizes divisible by 4 pixels in 8-bit mode (4 bytes). I have verified it on real hardware and it works.

Does this "should" mean that using lines divisible by 4 bytes is supported too? Are there any bad consequences to doing that?

Thanks

[Sanket_Parekh]

Hi @dcz 

Have you verified 780 bytes of data with divisible by 4 pixels in 8-bit mode?

Thanks & Regards

Sanket Parekh

[dcz]

I verified a 8-bit 780px width × 1052px height stream on i.MX8MQ.

[Sanket_Parekh]

Hi @dcz 

Waiting for your answer.

Thanks & Regards

Sanket Parekh

[dcz]

Correction: I verified a 8-bit 1052px width × 780px height stream

[Sanket_Parekh]

Hi @dcz 

That's great the streaming is working fine with 8-bit configuration.

Can you please verify the 8-bit configuration using transmission of 780 bytes only?

Thanks & Regards

Sanket Parekh

[dcz]

Hi,
if you mean 780px width x 1px height, then nothing similar to this did not work last time I tried: the height must be an even number if the width is not divisible by 8.

(I tried 1052px × 779px and that failed).

[Sanket_Parekh]

Hi @dcz 

1052px width × 780px This combinations was worked because both the values height and width are divisible by 4. That's why this combination was worked.

Thanks & Regards

Sanket Parekh

[dcz]

Thank you for the answer. Do I understand correctly, that streams divisible by 4×4 will work on other i.MX8 hardware too?

Will those kind of resolutions work on i.MX7 series CSI hardware?

[Sanket_Parekh · Accepted solution]

Hi @dcz 

Thank you for the answer. Do I understand correctly, that streams divisible by 4×4 will work on other i.MX8 hardware too? - Yes

Will those kind of resolutions work on i.MX7 series CSI hardware? - Yes

Thanks & Regards

Sanket Parekh