[Bug 101852] [BAT][GDG] igt at drv_hangman@error-state-basic incomplete in CI

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101852

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #20 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit 0db8c961209153498fe7e279b8f0d3deb81808f0
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Wed Sep 6 12:14:05 2017 +0100

    drm/i915: Re-enable GTT following a device reset

    Ville Syrjälä spotted that PGETBL_CTL was losing its enable bit upon a
    reset. That was causing the display to show garbage on his 945gm. On my
    i915gm the effect was far more severe; re-enabling the display following
    the reset without PGETBL_CTL being enabled lead to an immediate hard
    hang.

    We do have a routine to re-enable PGETBL_CTL which is applicable to
    gen2-4, although on gen4 it is documented that a graphics reset doesn't
    alter the register (no such wording is given for gen3) and should be safe
    to call to punch back in the enable bit. However, that leaves the question
    of whether we need to completely re-initialise the register and the
    rest of the GSM. For g33/pnv/gen4+, where we do have a configurable
    page table, its contents do seem to be kept, and so we should be able to
    recover without having to reinitialise the GTT from scratch (as prior to
    g33, that register is configured by the BIOS and we leave alone except
    for the enable bit).

    This appears to have been broken by commit 5fbd0418eef2 ("drm/i915:
    Re-enable GGTT earlier during resume on pre-gen6 platforms"), which
    moved the intel_enable_gtt() from i915_gem_init_hw() (also used by
    reset) to add it earlier during hw init and resume, missing the reset
    path.

    v2: Find the culprit, rearrange ggtt_enable to be before gem_init_hw to
    match init/resume

    Reported-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Fixes: 5fbd0418eef2 ("drm/i915: Re-enable GGTT earlier during resume on
pre-gen6 platforms")
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101852
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Cc: Daniel Vetter <daniel at ffwll.ch>
    Reviewed-by: Daniel Vetter <daniel at ffwll.ch>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20170906111405.27110-1-chris@chris-wilson.co.uk
    Tested-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

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