[Bug 92841] Linux 4.3 on Broadwell with i915.enable_fdc=0: "Unclaimed register detected after writing to register 0x4510c"

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=92841

--- Comment #1 from Adam J. Richter <adam_richter2004 at yahoo.com> ---
I don't know how I missed this:

$ egrep -i 4510c drivers/gpu/drm/i915/*.h
drivers/gpu/drm/i915/i915_reg.h:#define WM2_LP_ILK        0x4510c

The only .c file containing the string WM2_LP_ILK is
drivers/gpu/drm/i915/intel_pm.c, and the term "watermark" appears close to
those uses, so I guess that is what "WM" stands for.

It looks like this register is written unconditionally in
ilk_init_lp_watermarks, and I am just guessing from the function name that it
gets executed at initialization, so maybe there is something wrong with the
other debugging code that I added.

I expect I'll look into this tomorrow, but wanted to post this update now to
avoid prompting anyone else do this bit of research that I should have done
before posting.  I apologize for not including this information in my initial
bug report.

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