[Intel-gfx] [PATCH] drm/i915: Move init_clock_gating() back to where it was

[Chris Wilson]

Quoting Ville Syrjala (2017-11-03 13:03:37)
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Apparently setting up a bunch of GT registers before we've properly
> initialized the rest of the GT hardware leads to these setting being
> lost. So looks like I broke HSW with commit b7048ea12fbb ("drm/i915:
> Do .init_clock_gating() earlier to avoid it clobbering watermarks")
> by doing init_clock_gating() too early. This should actually affect
> other platforms as well, but apparently not to such a great degree.
> 
> What I was ultimately after in that commit was to move the
> ilk_init_lp_watermarks() call earlier. So let's undo the damage and
> move init_clock_gating() back to where it was, and call
> ilk_init_lp_watermarks() just before the watermark state readout.
> 
> This highlights how fragile and messed up our init order really is.
> I wonder why we even initialize the display before gem. The opposite
> order would make much more sense to me...
> 
> Cc: stable at vger.kernel.org
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mark Janes <mark.a.janes at intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Oscar Mateo <oscar.mateo at intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Reported-by: Mark Janes <mark.a.janes at intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103549
> Fixes: b7048ea12fbb ("drm/i915: Do .init_clock_gating() earlier to avoid it clobbering watermarks")
> References: https://lists.freedesktop.org/archives/intel-gfx/2017-November/145432.html
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Wrt to the reported CTS regressions, they are fixed.
Tested-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris