drm/i915/gen9: Verify and enforce dc6 state writes
authorMika Kuoppala <mika.kuoppala@linux.intel.com>
Thu, 18 Feb 2016 15:58:09 +0000 (17:58 +0200)
committerImre Deak <imre.deak@intel.com>
Mon, 22 Feb 2016 15:18:47 +0000 (17:18 +0200)
commit779cb5d3ddd72950ec726f86e38f7575c7fbdd4c
tree19dc72fc325083ec1993e6dcdd7f97e9046bdf33
parent832dba889e27487c3087149f1039acc3feb89003
drm/i915/gen9: Verify and enforce dc6 state writes

It has been observed that sometimes disabling the dc6 fails
and dc6 state pops back up, brief moment after disabling. This
has to be dmc save/restore timing issue or other bug in the
way dc states are handled.

Try to work around this issue as we don't have firmware fix
yet available. Verify that the value we wrote for the dmc sticks,
and also enforce it by rewriting it, if it didn't.

v2: Zero rereads on rewrite for extra paranoia (Imre)

Testcase: kms_flip/basic-flip-vs-dpms
References: https://bugs.freedesktop.org/show_bug.cgi?id=93768
Cc: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1455811089-27884-1-git-send-email-mika.kuoppala@intel.com
drivers/gpu/drm/i915/intel_runtime_pm.c