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>

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 1959148..5b039ca 100644 (file)
--- 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);