[PATCH] drm/gma500: Add CedarView LVDS blacklist

[Patrik Jakobsson]

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.

Thanks
Patrik

>
> Regards,
> Dominik
> --
> Fedora   https://getfedora.org  |  RPM Fusion  http://rpmfusion.org
> There should be a science of discontent. People need hard times and
> oppression to develop psychic muscles.
>         -- from "Collected Sayings of Muad'Dib" by the Princess Irulan