Re: 282dbf9b "drm/i915: Pass intel_plane and intel_crtc to plane hooks" breaks i945GM in 4.13 and above

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 11 Jan 2018, Karl-Johan Karlsson <creideiki+intel-gfx@ferretporn.se> wrote:
> Hello,
>
> I have an old Lenovo Thinkpad X60 laptop with a Core 2 Duo T7200 CPU and 
> i945GM integrated graphics whose graphics broke when I tried to update the 
> kernel to get the Meltdown fixes.
>
> GRUB2 shows a graphical boot menu, and Linux displays the Tux boot logos 
> correctly at first. However, almost immediately after displaying the Tuxes, 
> the actively scrolling area of the display shifts about two text lines 
> downward, so that two decapitated penguin heads are left at the top of the 
> screen and new text appears below the lower edge of the screen. When X starts, 
> it too is shifted down the same amount, and only shows a black screen with a 
> (working) mouse cursor. My display manager (SDDM) never shows up. Sometimes, 
> while X is running, random pixels appear in the non-active area at the top of 
> the screen containing the decapitated penguin heads.
>
> My hardware is:
>
> $ grep name /proc/cpuinfo
> model name      : Intel(R) Core(TM)2 CPU         T7200  @ 2.00GHz
> model name      : Intel(R) Core(TM)2 CPU         T7200  @ 2.00GHz
>
> # lspci | grep VGA
> 00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS, 
> 943/940GML Express Integrated Graphics Controller (rev 03)
>
> # grep Chipset: /var/log/Xorg.0.log
> [    33.085] (--) intel(0): Integrated Graphics Chipset: Intel(R) 945GM
>
> $ xrandr | grep primary
> LVDS1 connected primary 1024x768+0+0 (normal left inverted right x axis y 
> axis) 250mm x 180mm
>
> Kernel 4.12.14 does not have the bug. 4.13 and 4.14.11 have the bug in console 
> and X mode. 4.15-rc7 has the bug in console mode, but crashes (completely 
> black screen, Magic SysRq to reboot is the only thing that works) when 
> starting X.
>
> Bisecting from 4.12 to 4.13 pointed to this as the first bad commit:
>
> commit 282dbf9b017bc6d5fdaeadf14e534c2fe22fee2d
> Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Date:   Mon Mar 27 21:55:33 2017 +0300
>
>     drm/i915: Pass intel_plane and intel_crtc to plane hooks
>
> But I know nothing about the driver internals to explain why.

I'm afraid that bisect result doesn't seem plausible. Eyeballing through
it, it's just straightforward mechanical non-functional changes.

Please file a bug over at [1]. Please add drm.debug=14 module parameter,
attach dmesg and Xorg.0.log from boot. Please try confirming the bisect
result by running 282dbf9b017b and 282dbf9b017b^.

BR,
Jani.


[1] https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel



-- 
Jani Nikula, Intel Open Source Technology Center
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