SN75DP159: Inter lane skew is inconsistent in the DP159 output and is not compliant with DP spec when using it in DP to DP retimer mode.

Aravind

The DP159 inter-pair de-skew function is disabled when it acts as a DP retimer, so the de-skew function needs to be handled by the DP sink.

Thanks

David 

Hi David,

DP sink will deskew only as mentioned in DP spec.

DP159 receives data with inter lane skew as mentioned in DP specification. But the DP159 output is having inconsistent skew which is not matching with skew at it's inputs. DP159 is adding inconsistent and random interlane skew while transmitting the data on it's outputs.

Could you please let me know if there is any solution for this problem.

My problem is similar as the one in the below ticket. I didn't find a solution in that ticket. That's why I raised a new ticket. Please let me know how is the issue resolved.

https://e2e.ti.com/support/interface/f/138/t/741114

Regards,
Aravind.

Aravind

With inter-pair de-skew function being disabled in DP159, there are very few options for us to work around this issue, we have to rely on the sink to handle the de-skew.

Thanks

David

My sink can't dynamically deskew the lanes. It is fixed to 20UI per adjacent lane as defined in the DP spec. Is there any way we could use DP159 to bypass the data without doing anything?

Aravind

Are you following the DP159 power-up initialization configuration as listed in section 4 of the app note?

Thanks

David

Yes. I'm following the initialization and every other programming sequence as mentioned in the app note.

I don't need DP159 to deskew the data. I need it to maintain the interlane skew which is already there in the inputs. In my case DP159 is inconsistently varying the interlane skew. On every reset and re initialization, the interlane skew on the outputs of DP159 varies. I want to know if we can fix this by any means. I've made sure that everything was followed as per the DP159 specification and app note.

What happens when there is an interlane skew in the inputs of DP159? Will it maintain that skew or will it be unable to determine the skew on it's output. My assumption is that DP159 being DP1.2 compatible, it should maintain the interlane skew. Correct me if I'm wrong.

Aravind

Can you please program the DP159 into the redrive mode only by writing 'b0x00 to DEV_FUNC_MODE (register 0x0A)? 

Thanks

David