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: Fri, 10 Jan 2020 16:50:55 +0100	[thread overview]
Message-ID: <CAEsyxyj1bR2zuXFegE2B0FMoN8nrct84QCpY7HsF4P-6ZKY4Cw@mail.gmail.com> (raw)
In-Reply-To: <20200110133232.GJ13686@intel.com>

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On Fri, Jan 10, 2020 at 2:32 PM Ville Syrjälä <ville.syrjala@linux.intel.com>
wrote:

> On Thu, Jan 09, 2020 at 09:19:07PM +0100, Mario Kleiner wrote:
> > 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.
>
> It can take a while to dump the whole thing. If there are errors in some
> parts (against the spec but some devices simply don't care about the
> spec) you may need to use ddrescue/etc. to dump everything that can be
> dumped.
>
> Ok, it is Mozilla bug 206157:

https://bugzilla.kernel.org/show_bug.cgi?id=206157

I attached the first ~ 5000 Bytes of DPCD dump, as there is a 5k file size
limit. The total dump is 512 kB, mostly zeros.

-mario

-- 
> Ville Syrjälä
> Intel
>

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