drm/i915: add support for checking RPM atomic sections

In some cases we want to check whether we hold an RPM wakelock reference
for the whole duration of a sequence. To achieve this add a new RPM
atomic sequence counter that we increment any time the wakelock refcount
drops to zero.  Check whether the sequence number stays the same during
the atomic section and that we hold the wakelock at the beginning of the
section.

Motivated by Chris.

v2-v3:
- unchanged
v4:
- swap the order of atomic_read() and assert_rpm_wakelock_held() in
  assert_rpm_atomic_begin() to avoid race

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> (v3)
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1450203038-5150-10-git-send-email-imre.deak@intel.com

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 74f1d78cbe2e..1943b8f0e684 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1606,6 +1606,7 @@ struct skl_wm_level {
  */
 struct i915_runtime_pm {
 	atomic_t wakeref_count;
+	atomic_t atomic_seq;
 	bool suspended;
 	bool irqs_enabled;
 };