[Intel-gfx] [PATCH] drm/i915: Update bits to check in device class from VBT to detect eDP

[Kumar, Shobhit]

On 6/5/2014 9:34 PM, Jesse Barnes wrote:
> On Thu, 5 Jun 2014 16:09:29 +0300
> Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
>
>> On Thu, Jun 05, 2014 at 06:25:13PM +0530, Shobhit Kumar wrote:
>>> The DEVICE_TYPE_eDP has been changed to 0x1806 in case of BYT which
>>> can causes wrong detection failures for eDP. Reduce the number of bits
>>> of interest in DEVICE_TYPE_eDP_BITS to just check most relevant and
>>> conclusive ones and ensure they are set in device_class from VBT. This
>>> will ensure that eDP detection works across platforms
>>
>> The current bits will match correctly for 0x1806. I don't have a problem
>> with the patch per-say but would be nice to know what the troublesome
>> device type really was, if indeed there was one. I'm just slightly
>> worried that we might start to get false positives on some platforms if
>> we make it too relaxed.
>
> Still waiting for results, but
> https://bugs.freedesktop.org/show_bug.cgi?id=78795 was what motivated this.
>

Yeah and update from Jesse that forcefully returning true from the 
function make things work, I assumed this is the reason, without really 
checking that even the old values will result DEVIVE_TYPE_eDP & 
DEVICE_TYPE_eDP_BITS = 0x1806 :)

Nevertheless I still feel that a simplified bit mask is good to have. We 
need to check further on this issue Jesse. Let me know once you have 
results. It would be still better to spit out the device_type being read 
from VBT as a log to confirm that indeed it is coming as 0x1806 or can 
just ask to get the opregion dump from debugfs and we can check ourselves.

Regards
Shobhit