[Bug 90469] [BYT dsi] WARNING: CPU: 3 PID: 265 at drivers/gpu/drm/drm_irq.c:1130 drm_wait_one_vblank+0x177/0x180()

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90469

Jani Nikula <jani.nikula at intel.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |NEEDINFO

--- Comment #53 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to Laszlo Fiat from comment #51)
> I found the commit that makes my DSI display go blank (and causes the
> WARNING) when the KMS loads with kernels newer than linux-next-20151119:
> 
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/
> drivers/gpu/drm/i915?id=7383123647566a813692bb37a1389c767ed89158
> 
> Revert "drm/i915: skip modeset if compatible for everyone."
> 
> This commit brings back the i915.fastboot parameter in disabled state, and
> with that the DSI screen goes blank when KMS loads. 
> 
> Adding i915.fastboot=1 kernel bootline parameter to a recent v4.6 RC4 kernel
> enables my Teclast X80h tablet to boot with the DSI screen enabled.

Sorry, the earlier regressions trumps the later one, so we'll have to keep the
revert, for now.

Also, i915.fastboot=1 tries to skip modeset at module load, so presumably our
DSI modeset for your panel doesn't work. I suspect a modeset might fail if you
tried it after booting with i915.fastboot=1.

Please also attach /sys/kernel/debug/dri/0/i915_vbt

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