Re: [PATCH] drm/i915/dp: Add current maximum eDP link rate to sink_rate array.

From: Mario Kleiner <mario.kleiner.de@gmail.com>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: mario.kleiner.de@gmail.de,
	intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Daniel Vetter <daniel.vetter@ffwll.ch>
Subject: Re: [PATCH] drm/i915/dp: Add current maximum eDP link rate to sink_rate array.
Date: Thu, 9 Jan 2020 21:19:07 +0100	[thread overview]
Message-ID: <CAEsyxyiTxRZC=Mw4rKvjCQO557Qg6Q2JRkoUvQWOia7SxumznA@mail.gmail.com> (raw)
In-Reply-To: <20200109182408.GF13686@intel.com>

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On Thu, Jan 9, 2020 at 7:24 PM Ville Syrjälä <ville.syrjala@linux.intel.com>
wrote:

> On Thu, Jan 09, 2020 at 06:57:14PM +0100, Mario Kleiner wrote:
> > On Thu, Jan 9, 2020 at 5:47 PM Ville Syrjälä <
> ville.syrjala@linux.intel.com>
> > wrote:
> >
> > > On Thu, Jan 09, 2020 at 05:30:05PM +0100, Mario Kleiner wrote:
> > > > On Thu, Jan 9, 2020 at 4:38 PM Ville Syrjälä <
> > > ville.syrjala@linux.intel.com>
> > > > wrote:
> > > >
>

> wouldn't work if dpcd[0x1] == 0xa, which it likely is [*]. AMD DC
> > identified it as DP 1.1, eDP 1.3, and these extended caps seem to be only
> > part of DP 1.3+ if i understand the comments in
> > intel_dp_extended_receiver_capabilities() correctly.
>
>
Ok, looking at previous debug output logs shows that those extended caps
are not present on the systems, ie. that extended caps bit is not set. So
dpcd[0x1] == 0xa.

> Yeah, but you never know how creative they've been with the DPCD in
> such a propritary machine. A full DPCD dump from /dev/drm_dp_aux* would
> be nice. Can you file a bug an attach the DPCD dump there so we have a
> good reference on what we're talking about (also for future if/when
> someone eventually starts to wonder why we have such hacks in the
> code)?
>
>
True, it's Apple which likes to "Think different..." :/

Will do. But is there a proper/better way to do the /dev/drm_dp_aux0 dump?
I used cat /dev/drm_dp_aux0 > dump, and that hangs, but if i interrupt it
after a few seconds, i get a dump file of 512k size, which seems excessive?
On AMD DC atm., in case that matters.

However, the file shows DPCD_REV 1.1, maximum 0xa and no extended caps (
DP_TRAINING_AUX_RD_INTERVAL
<https://elixir.bootlin.com/linux/v5.5-rc5/ident/DP_TRAINING_AUX_RD_INTERVAL>
aka
[0xe] == 0x00).
 -mario

-- 
> Ville Syrjälä
> Intel
>

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