[Intel-gfx] Baytrail MIPI/DSI Black when boot with HDMI connected

[Pierre-Louis Bossart]

On 10/28/16 1:48 AM, Jani Nikula wrote:
> On Fri, 28 Oct 2016, Fabian Pie <fpie at teleker.com> wrote:
>> Hi,
>> I'm testing Baytrail device with mipi/dsi display and hdmi output. When I
>> boot without the hdmi connected the mipi/dsi works OK and after connecting
>> the hdmi both mipi/dsi and hdmi display graphics OK.
>> If I boot with the hdmi connected it's selected by the bios as the default
>> display, Ubuntu only boots in hdmi and it works OK in this display but
>> MIPI/DSI is black. It's listed as connected by xrandr but I can't reset in
>> any way.
>> I didn't find this issue in your bug list. Have you seen anything similar ?
>> I'm using Ubuntu 16.10 with kernel 4.8.4
>
> Probably the BIOS skips some DSI initialization in this case, and we
> fail to bring it up. Please file a bug over at [1], include the above
> description, add drm.debug=14 module parameter, attach dmesg all the way
> from boot for both the working and broken cases, plus
> /sys/kernel/debug/dri/0/i915_vbt.

Same issue on Asus T100TAF (Baytrail-CR)