[PATCH] drm/gma500: Add CedarView LVDS blacklist

[Hans de Goede]

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.

Regards,

Hans