[Intel-gfx] [PATCH 1/2] drm/dp: retry AUX transactions 32 times

[Dave Airlie]

On 26 November 2014 at 19:24, Jani Nikula <jani.nikula at linux.intel.com> wrote:
> On Wed, 26 Nov 2014, Dave Airlie <airlied at gmail.com> wrote:
>> From: Dave Airlie <airlied at redhat.com>
>>
>> At least on two MST devices I've tested with, when
>> they are link training downstream, they are totally
>> unable to handle aux ch msgs, so they defer like nuts.
>> I tried 16, it wasn't enough, 32 seems better.
>
> I think we have a bug with some dongle that defers a lot too. One idea
> was to use a progressively longer delay for DP_AUX_NATIVE_REPLY_DEFER.
>
> How about drm_dp_i2c_do_msg(), that one can receive native aux defer
> too, along with i2c defer. It feels like both places should have the
> same limit for native aux defer, but if you want to keep different i2c
> defer retry limit it gets a bit trickier.

I think we want to keep the spec limit there, since its in the spec,

But you might be right on wanting to extend the defer therre as well if
we can, I'll probably tackle that in a second patch.

Dave.