[PATCHv2 13/22] drm/bridge: tc358767: use more reliable seq when finishing LT

Tomi Valkeinen tomi.valkeinen at ti.com
Fri May 3 11:04:18 UTC 2019


On 21/04/2019 00:44, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Tue, Mar 26, 2019 at 12:31:37PM +0200, Tomi Valkeinen wrote:
>> At the end of the link training, two steps have to be taken: 1)
>> tc358767's LT mode is disabled by a write to DP0_SRCCTRL, and 2) Remove
>> LT flag in DPCD 0x102.
>>
>> Toshiba's documentation tells to first write the DPCD, then modify
>> DP0_SRCCTRL. In my testing this often causes issues, and the link
>> disconnects right after those steps.
>>
>> If I reverse the steps, it works every time. There's a chance that this
>> is DP sink specific, though, but as my testing shows this sequence to be
>> much more reliable, let's change it.
> 
> As this departs from the documentation I think it deserves a comment in
> the code.

Yep. It's not exactly documentation, but just an excel sheet that they
use for testing. The actual documentation doesn't talk about this.

I'll add a comment.

 Tomi

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