[PATCH] drm/gma500: Add CedarView LVDS blacklist

[Patrik Jakobsson]

On Wed, Apr 10, 2019 at 9:27 AM Hans de Goede <hdegoede at redhat.com> wrote:
>
> Hi,
>
> On 09-04-19 21:31, Dominik 'Rathann' Mierzejewski wrote:
> > Hello,
> >
> > On Tuesday, 09 April 2019 at 16:44, Hans de Goede wrote:
> >> Hi,
> >>
> >> On 09-04-19 14:05, Patrik Jakobsson wrote:
> >>> On Tue, Apr 9, 2019 at 12:20 PM Hans de Goede <hdegoede at redhat.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> On 09-04-19 11:47, Patrik Jakobsson wrote:
> >>>>> On Tue, Apr 9, 2019 at 8:51 AM Hans de Goede <hdegoede at redhat.com> wrote:
> >>>>>>
> >>>>>> Some CedarView VBT-s claim that there is a LVDS panel, while there is none.
> >>>>>> Specifically this happens on the Thecus N2800 / N5550 NAS models.
> >>>>>>
> >>>>>> This commit adds a LVDS blacklist to deal with this and adds an entry for
> >>>>>> the Thecus NAS-es.
> >>>>>
> >>>>> Hi Hans,
> >>>>> Sometimes LVDS can be configured in the BIOS on CDV devices. Can you
> >>>>> check that it's not just a bad BIOS configuration first?
> >>>>
> >>>> I've asked the reporter to test, but even if there is a BIOS option it
> >>>> seems that the BIOS default setting is wrong and we cannot expect every
> >>>> user to go into the BIOS to fix a wrong BIOS setting.
> >>>>
> >>>> According to this blogpost, which is about the Linux the device ships with:
> >>>> https://astroweasel.blogspot.com/2016/02/updating-thecus-n5550-nas-to-report.html
> >>>>
> >>>> The pre-installed grub config includes 'video=LVDS-1:d' on the kernel
> >>>> commandline, so this clearly seems to be a case where the system is just
> >>>> shipping with a broken BIOS or at least with default BIOS settings which
> >>>> is just as bad.
> >>>
> >>> I agree that we should try to fix a broken default but are you sure
> >>> this will only affect the n5550? IIUC Milstead / Granite Well is an
> >>> Intel product / board name and perhaps some of those use LVDS.
> >>
> >> Milstead is the name of Intel's NAS reference design:
> >>
> >> https://www.hardwarezone.com.my/tech-news-intel-unveils-milstead-platform-nas-devices
> >>
> >> I seriously doubt that any NAS-es have a LVDS (laptop/tablet) LCD panel.
> >>
> >>> Also, if the pre-installed OS solves this on the cmdline then it's
> >>> only a problem if the user is trying to install a custom OS on the
> >>> device. I would expect such a user to be able to change bios settings.
> >>>
> >>> 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.

>
> Regards,
>
> Hans
>