[Bug 59841] [IVB cpu eDP] panel is broken due to 657445fe86 (eDP bpp clamping)

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=59841

ZeroBit <Lyshenko at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |Lyshenko at gmail.com

--- Comment #44 from ZeroBit <Lyshenko at gmail.com> ---
> Created attachment 107199 [details]
> never use bios provided bpp, but log the value
> 
> Booting 3.11-rc5 works fine from legacy mode. (see my previous comment)
> Booting from uefi mode triggers this bug (and the very dark screen bug that
> was described here too on the dell xps 13). Using the provided patch and
> booting once from legacy and on uefi mode, gives the following results.
> 
> legacy mode - working without the patch:
> [    1.570344] [drm:intel_dp_compute_config], BPPHACK -
> pipe_config->pipe_bpp: 24, dev_priv->vbt.edp_bpp: 24
> 
> uefi-mode - not working without the patch:
> [    1.772969] [drm:intel_dp_compute_config], BPPHACK -
> pipe_config->pipe_bpp: 24, dev_priv->vbt.edp_bpp: 18
> 
> ---
> OT: brightness controls
> 3.11-rc5 seems to be the first kernel I tried, where brightness control
> work, when booting in legacy mode. It does not work in UEFI mode though,
> that used to work when using acpi_backlight=vendor.

I confirm the same with ASUS Zenbook ux32vd 
This patch https://bugzilla.kernel.org/attachment.cgi?id=107199&action=diff
really works fine with 3.11 kernel allowing brightness controls with
"acpi_osi="

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