[PATCH] drm/gma500: Add CedarView LVDS blacklist

[Dominik 'Rathann' Mierzejewski]

On Wednesday, 10 April 2019 at 13:33, Patrik Jakobsson wrote:
> On Wed, Apr 10, 2019 at 1:18 PM Dominik 'Rathann' Mierzejewski
> <dominik at greysector.net> wrote:
> >
> > On Wednesday, 10 April 2019 at 11:08, Hans de Goede wrote:
> > > On 10-04-19 11:00, Patrik Jakobsson wrote:
> > > > On Wed, Apr 10, 2019 at 9:27 AM Hans de Goede <hdegoede at redhat.com> wrote:
> > > > > On 09-04-19 21:31, Dominik 'Rathann' Mierzejewski wrote:
> > > > > > On Tuesday, 09 April 2019 at 16:44, Hans de Goede wrote:
> > > > > > > On 09-04-19 14:05, Patrik Jakobsson wrote:
> > [...]
> > > > > > > > I'm not totally against this but not sure about the consequences. Is
> > > > > > > > there perhaps a better dmi string to match against?
> > > > > > >
> > > > > > > No there are no better DMI strings to match against I'm afraid.
> > > > > >
> > > > > > I did load default settings in BIOS setup and there's no change in
> > > > > > behaviour. LVDS gets detected as connected:
> > > > > > $ cat /sys/class/drm/card0-LVDS-1/status
> > > > > > connected
> > > > > >
> > > > > > Only VGA output is physically connected at the moment.
> > > > >
> > > > > To be clear what Dominik means here is that he has a VGA monitor
> > > > > connected. There is no LVDS panel in this device at all.
> > > >
> > > > Thanks for testing. I dusted off my DN2800MT and tried turning LVDS
> > > > on/off in the BIOS. With LVDS disabled gma500 reports it as connected.
> > > > When LVDS is enabled in bios I instead get a connected eDP connector.
> > > > I'm starting to think that broken VBT parsing might be the actual
> > > > problem.
> > >
> > > Maybe, but I assume there are CedarView based laptops with LVDS panels
> > > which works, so I suspect this might be more of a bug in your BIOS.
> > >
> > > So what is the next step in debugging this?
> >
> > To add a small twist, I got an updated BIOS from the vendor to fix
> > another issue (https://bugzilla.kernel.org/show_bug.cgi?id=199117)
> > and the DMI string has changed to: "CDV W Series 05", so Hans' patch
> > no longer matches my machine.
> 
> Hi Dominik,
> 
> Do you have any option to enable/disable LVDS in your BIOS. The BIOS
> default might not be to disable LVDS since they apparently solved the
> issue on the command line anyway. If there is an option to turn it off
> but you still get the same problem, then it is possible that detection
> of "LVDS disabled" in the driver might be bad.

No, there's no option to enable/disable LVDS. The machine is a NAS box
and doesn't have an LVDS physically. You can see the motherboard e.g.
here: https://youtu.be/ZYNQvZNGLsE?t=855 .

Regards,
Dominik
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