[Bug 102249] [CI][HSW] Unclaimed read from register 0x70008

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https://bugs.freedesktop.org/show_bug.cgi?id=102249

--- Comment #1 from Chris Wilson <chris at chris-wilson.co.uk> ---
Daniel suggested this might be related to

commit 4055dc75d6b51c23602b11c6f716e59b8947ffbf
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu Aug 17 18:32:29 2017 +0100

    drm/i915: Stop touching forcewake following a gen6+ engine reset

    Forcewake is not affected by the engine reset on gen6+. Indeed the
    reason why we added intel_uncore_forcewake_reset() to
    gen6_reset_engines() was to keep the bookkeeping intact because the
    reset did not touch the forcewake bit (yet we cancelled the forcewake
    consumers)!  This was done in commit 521198a2e7095:
        Author: Mika Kuoppala <mika.kuoppala at linux.intel.com>
        Date:   Fri Aug 23 16:52:30 2013 +0300

            drm/i915: sanitize forcewake registers on reset

            In reset we try to restore the forcewake state to
            pre reset state, using forcewake_count. The reset
            doesn't seem to clear the forcewake bits so we
            get warn on forcewake ack register not clearing.

    That futzing of the forcewake bookkeeping was dropped in commit
    0294ae7b44bb ("drm/i915: Consolidate forcewake resetting to a single
    function"), but it did not make the realisation that the remaining
    intel_uncore_forcewake_reset() was redundant.

    The new danger with using intel_uncore_forcewake_reset() with per-engine
    resets is that the driver and hw are still in an active state as we
    perform the reset. We may be using the forcewake to read protected
    registers elsewhere and those results may be clobbered by the concurrent
    dropping of forcewake.

but I was not convinced. On the off chance I was wrong...

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