RE: [PATCH 2/3] drm/i915/dp: read Aux RD interval after reading the FFE preset

["Srikanth V, NagaVenkata" <nagavenkata.srikanth.v@xxxxxxxxx>]

Hi Jani,

 

It's as per DP2.1 spec, where we should be reading AUX_RD interval at the loop before we wait.

Regards

Srikanth

 

-----Original Message-----
From: Murthy, Arun R <arun.r.murthy@xxxxxxxxx>
Sent: Thursday, September 12, 2024 4:25 PM
To: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>; intel-xe@xxxxxxxxxxxxxxxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Srikanth V, NagaVenkata <nagavenkata.srikanth.v@xxxxxxxxx>
Subject: RE: [PATCH 2/3] drm/i915/dp: read Aux RD interval after reading the FFE preset

 

> On Thu, 12 Sep 2024, Arun R Murthy <arun.r.murthy@xxxxxxxxx> wrote:

> > DP Source should be reading AUX_RD interval after we get adjusted

> > TX_FFE_PRESET_VALUE from the DP Sink. (before actually adjusting in

> > DP

> > Source)

>

> Please explain why.

As per the DP 2.1 spec section 3.5.2.16.1 "The transmitter shall finish reading from DPCD 00202h through 00207h, DPCD 0200Ch through 0200Fh, and DPCD 02216h, and writing to DPCD 00103h through 00106h (listed as “AUX TX response” in Figure 3-51) within

2.5 ms or less, such that the total duration for AUX TX responses with a 20-loop count does not exceed 50 ms. "

 

Thanks and Regards,

Arun R Murthy

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