drm/i915: Add support for tracking wakerefs w/o power-on guarantee

It's useful to track runtime PM refs that don't guarantee a device
power-on state to the rest of the driver. One such case is holding a
reference that will be put asynchronously, during which normal users
without their own reference shouldn't access the HW. A follow-up patch
will add support for disabling display power domains asynchronously
which needs this.

For this we can split wakeref_count into a low half-word tracking
all references (raw-wakerefs) and a high half-word tracking
references guaranteeing a power-on state (wakelocks).

Follow-up patches will make use of the API added here.

While at it add the missing docbook header for the unchecked
display-power and runtime_pm put functions.

No functional changes, except for printing leaked raw-wakerefs
and wakelocks separately in intel_runtime_pm_cleanup().

v2:
- Track raw wakerefs/wakelocks in the low/high half-word of
  wakeref_count, instead of adding a new counter. (Chris)
v3:
- Add a struct_member(T, m) helper instead of open-coding it. (Chris)
- Checkpatch indentation formatting fix.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190509173446.31095-2-imre.deak@intel.com

1 files changed, 47 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 5258abb2ebb5..30b2d6ed2d53 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1620,6 +1620,24 @@ unsigned int i9xx_plane_max_stride(struct intel_plane *plane,
 int bdw_get_pipemisc_bpp(struct intel_crtc *crtc);
 
 /* intel_runtime_pm.c */
+#define BITS_PER_WAKEREF	\
+	BITS_PER_TYPE(struct_member(struct i915_runtime_pm, wakeref_count))
+#define INTEL_RPM_WAKELOCK_SHIFT	(BITS_PER_WAKEREF / 2)
+#define INTEL_RPM_WAKELOCK_BIAS		(1 << INTEL_RPM_WAKELOCK_SHIFT)
+#define INTEL_RPM_RAW_WAKEREF_MASK	(INTEL_RPM_WAKELOCK_BIAS - 1)
+
+static inline int
+intel_rpm_raw_wakeref_count(int wakeref_count)
+{
+	return wakeref_count & INTEL_RPM_RAW_WAKEREF_MASK;
+}
+
+static inline int
+intel_rpm_wakelock_count(int wakeref_count)
+{
+	return wakeref_count >> INTEL_RPM_WAKELOCK_SHIFT;
+}
+
 static inline void
 assert_rpm_device_not_suspended(struct i915_runtime_pm *rpm)
 {
@@ -1628,11 +1646,33 @@ assert_rpm_device_not_suspended(struct i915_runtime_pm *rpm)
 }
 
 static inline void
-__assert_rpm_wakelock_held(struct i915_runtime_pm *rpm)
+____assert_rpm_raw_wakeref_held(struct i915_runtime_pm *rpm, int wakeref_count)
 {
 	assert_rpm_device_not_suspended(rpm);
-	WARN_ONCE(!atomic_read(&rpm->wakeref_count),
-		  "RPM wakelock ref not held during HW access");
+	WARN_ONCE(!intel_rpm_raw_wakeref_count(wakeref_count),
+		  "RPM raw-wakeref not held\n");
+}
+
+static inline void
+____assert_rpm_wakelock_held(struct i915_runtime_pm *rpm, int wakeref_count)
+{
+	____assert_rpm_raw_wakeref_held(rpm, wakeref_count);
+	WARN_ONCE(!intel_rpm_wakelock_count(wakeref_count),
+		  "RPM wakelock ref not held during HW access\n");
+}
+
+static inline void
+assert_rpm_raw_wakeref_held(struct drm_i915_private *i915)
+{
+	struct i915_runtime_pm *rpm = &i915->runtime_pm;
+
+	____assert_rpm_raw_wakeref_held(rpm, atomic_read(&rpm->wakeref_count));
+}
+
+static inline void
+__assert_rpm_wakelock_held(struct i915_runtime_pm *rpm)
+{
+	____assert_rpm_wakelock_held(rpm, atomic_read(&rpm->wakeref_count));
 }
 
 static inline void
@@ -1662,7 +1702,8 @@ assert_rpm_wakelock_held(struct drm_i915_private *i915)
 static inline void
 disable_rpm_wakeref_asserts(struct drm_i915_private *i915)
 {
-	atomic_inc(&i915->runtime_pm.wakeref_count);
+	atomic_add(INTEL_RPM_WAKELOCK_BIAS + 1,
+		   &i915->runtime_pm.wakeref_count);
 }
 
 /**
@@ -1679,7 +1720,8 @@ disable_rpm_wakeref_asserts(struct drm_i915_private *i915)
 static inline void
 enable_rpm_wakeref_asserts(struct drm_i915_private *i915)
 {
-	atomic_dec(&i915->runtime_pm.wakeref_count);
+	atomic_sub(INTEL_RPM_WAKELOCK_BIAS + 1,
+		   &i915->runtime_pm.wakeref_count);
 }
 
 #endif /* __INTEL_DRV_H__ */