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

[Srikanth V, NagaVenkata]

Hi Jani,



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

[cid:image001.png at 01DB0538.65998930]

Regards

Srikanth



-----Original Message-----
From: Murthy, Arun R <arun.r.murthy at intel.com>
Sent: Thursday, September 12, 2024 4:25 PM
To: Jani Nikula <jani.nikula at linux.intel.com>; intel-xe at lists.freedesktop.org; intel-gfx at lists.freedesktop.org
Cc: Srikanth V, NagaVenkata <nagavenkata.srikanth.v at intel.com>
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 at intel.com<mailto:arun.r.murthy at intel.com>> 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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