drm/i915: sanity check power well sw state against hw state

Suggested by Daniel.

v2:
- sanitize the state checking condition, the original was rather
  confusing (partly due to the unfortunate naming of
  i915.disable_power_well) (Ville)
- simpler message+backtrace generation by using WARN instead of WARN_ON
  (Ville)
- check if always-on power wells are truly on all the time

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 35 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 19591488fd2a..5b039ca13927 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5411,6 +5411,29 @@ static bool i9xx_always_on_power_well_enabled(struct drm_i915_private *dev_priv,
         return true;
 }
 
+static void check_power_well_state(struct drm_i915_private *dev_priv,
+                                   struct i915_power_well *power_well)
+{
+        bool enabled = power_well->ops->is_enabled(dev_priv, power_well);
+
+        if (power_well->always_on || !i915.disable_power_well) {
+                if (!enabled)
+                        goto mismatch;
+
+                return;
+        }
+
+        if (enabled != (power_well->count > 0))
+                goto mismatch;
+
+        return;
+
+mismatch:
+        WARN(1, "state mismatch for '%s' (always_on %d hw state %d use-count %d disable_power_well %d\n",
+                  power_well->name, power_well->always_on, enabled,
+                  power_well->count, i915.disable_power_well);
+}
+
 void intel_display_power_get(struct drm_i915_private *dev_priv,
                              enum intel_display_power_domain domain)
 {
@@ -5422,9 +5445,14 @@ void intel_display_power_get(struct drm_i915_private *dev_priv,
 
         mutex_lock(&power_domains->lock);
 
-        for_each_power_well(i, power_well, BIT(domain), power_domains)
-                if (!power_well->count++)
+        for_each_power_well(i, power_well, BIT(domain), power_domains) {
+                if (!power_well->count++) {
+                        DRM_DEBUG_KMS("enabling %s\n", power_well->name);
                         power_well->ops->enable(dev_priv, power_well);
+                }
+
+                check_power_well_state(dev_priv, power_well);
+        }
 
         power_domains->domain_use_count[domain]++;
 
@@ -5448,8 +5476,12 @@ void intel_display_power_put(struct drm_i915_private *dev_priv,
         for_each_power_well_rev(i, power_well, BIT(domain), power_domains) {
                 WARN_ON(!power_well->count);
 
-                if (!--power_well->count && i915.disable_power_well)
+                if (!--power_well->count && i915.disable_power_well) {
+                        DRM_DEBUG_KMS("disabling %s\n", power_well->name);
                         power_well->ops->disable(dev_priv, power_well);
+                }
+
+                check_power_well_state(dev_priv, power_well);
         }
 
         mutex_unlock(&power_domains->lock);