drm/i915: add intel_display_power_enabled_sw() for use in atomic ctx

Atm we call intel_display_power_enabled() from
i915_capture_error_state() in IRQ context and then take a mutex. To fix
this add a new intel_display_power_enabled_sw() which returns the domain
state based on software tracking as opposed to reading the actual HW
state.

Since we use domain_use_count for this without locking on the reader
side make sure we increase the counter only after enabling all required
power wells and decrease it before disabling any of these power wells.

Regression introduced in
commit 1b02383464b4a915627ef3b8fd0ad7f07168c54c
Author: Imre Deak <imre.deak@intel.com>
Date:   Tue Sep 24 16:17:09 2013 +0300

    drm/i915: support for multiple power wells

Note that atm we depend on the value returned by
intel_display_power_enabled_sw() in i915_capture_error_state() to avoid
unclaimed register access reports. This was never guaranteed though,
since another thread can disable the power concurrently. If this is a
problem we need another explicit way to disable the reporting during
error captures.

v2:
- remove barriers as the caller can't depend on the value
  returned from i915_capture_error_state_sw() anyway (Ville)
- dump the state of pipe/transcoder power domain state (Daniel)

Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -976,9 +976,7 @@ struct i915_power_domains {
 	int power_well_count;
 
 	struct mutex lock;
-#if IS_ENABLED(CONFIG_DEBUG_FS)
 	int domain_use_count[POWER_DOMAIN_NUM];
-#endif
 	struct i915_power_well *power_wells;
 };
 

drivers/gpu/drm/i915/intel_display.c

@@ -11317,6 +11317,7 @@ struct intel_display_error_state {
 	} cursor[I915_MAX_PIPES];
 
 	struct intel_pipe_error_state {
+		bool power_domain_on;
 		u32 source;
 	} pipe[I915_MAX_PIPES];
 
@@ -11331,6 +11332,7 @@ struct intel_display_error_state {
 	} plane[I915_MAX_PIPES];
 
 	struct intel_transcoder_error_state {
+		bool power_domain_on;
 		enum transcoder cpu_transcoder;
 
 		u32 conf;
@@ -11368,7 +11370,9 @@ intel_display_capture_error_state(struct drm_device *dev)
 		error->power_well_driver = I915_READ(HSW_PWR_WELL_DRIVER);
 
 	for_each_pipe(i) {
-		if (!intel_display_power_enabled(dev, POWER_DOMAIN_PIPE(i)))
+		error->pipe[i].power_domain_on =
+			intel_display_power_enabled_sw(dev, POWER_DOMAIN_PIPE(i));
+		if (!error->pipe[i].power_domain_on)
 			continue;
 
 		if (INTEL_INFO(dev)->gen <= 6 || IS_VALLEYVIEW(dev)) {
@@ -11404,8 +11408,9 @@ intel_display_capture_error_state(struct drm_device *dev)
 	for (i = 0; i < error->num_transcoders; i++) {
 		enum transcoder cpu_transcoder = transcoders[i];
 
-		if (!intel_display_power_enabled(dev,
-				POWER_DOMAIN_TRANSCODER(cpu_transcoder)))
+		error->transcoder[i].power_domain_on =
+			intel_display_power_enabled_sw(dev, POWER_DOMAIN_PIPE(i));
+		if (!error->transcoder[i].power_domain_on)
 			continue;
 
 		error->transcoder[i].cpu_transcoder = cpu_transcoder;
@@ -11440,6 +11445,8 @@ intel_display_print_error_state(struct drm_i915_error_state_buf *m,
 			   error->power_well_driver);
 	for_each_pipe(i) {
 		err_printf(m, "Pipe [%d]:\n", i);
+		err_printf(m, "  Power: %s\n",
+			   error->pipe[i].power_domain_on ? "on" : "off");
 		err_printf(m, "  SRC: %08x\n", error->pipe[i].source);
 
 		err_printf(m, "Plane [%d]:\n", i);
@@ -11465,6 +11472,8 @@ intel_display_print_error_state(struct drm_i915_error_state_buf *m,
 	for (i = 0; i < error->num_transcoders; i++) {
 		err_printf(m, "CPU transcoder: %c\n",
 			   transcoder_name(error->transcoder[i].cpu_transcoder));
+		err_printf(m, "  Power: %s\n",
+			   error->transcoder[i].power_domain_on ? "on" : "off");
 		err_printf(m, "  CONF: %08x\n", error->transcoder[i].conf);
 		err_printf(m, "  HTOTAL: %08x\n", error->transcoder[i].htotal);
 		err_printf(m, "  HBLANK: %08x\n", error->transcoder[i].hblank);

drivers/gpu/drm/i915/intel_drv.h

@@ -842,6 +842,8 @@ int intel_power_domains_init(struct drm_device *dev);
 void intel_power_domains_remove(struct drm_device *dev);
 bool intel_display_power_enabled(struct drm_device *dev,
 				 enum intel_display_power_domain domain);
+bool intel_display_power_enabled_sw(struct drm_device *dev,
+				    enum intel_display_power_domain domain);
 void intel_display_power_get(struct drm_device *dev,
 			     enum intel_display_power_domain domain);
 void intel_display_power_put(struct drm_device *dev,

drivers/gpu/drm/i915/intel_pm.c

@@ -5641,6 +5641,17 @@ static bool hsw_power_well_enabled(struct drm_device *dev,
 		     (HSW_PWR_WELL_ENABLE_REQUEST | HSW_PWR_WELL_STATE_ENABLED);
 }
 
+bool intel_display_power_enabled_sw(struct drm_device *dev,
+				    enum intel_display_power_domain domain)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct i915_power_domains *power_domains;
+
+	power_domains = &dev_priv->power_domains;
+
+	return power_domains->domain_use_count[domain];
+}
+
 bool intel_display_power_enabled(struct drm_device *dev,
 				 enum intel_display_power_domain domain)
 {
@@ -5761,12 +5772,11 @@ void intel_display_power_get(struct drm_device *dev,
 
 	mutex_lock(&power_domains->lock);
 
-#if IS_ENABLED(CONFIG_DEBUG_FS)
-	power_domains->domain_use_count[domain]++;
-#endif
 	for_each_power_well(i, power_well, BIT(domain), power_domains)
 		__intel_power_well_get(dev, power_well);
 
+	power_domains->domain_use_count[domain]++;
+
 	mutex_unlock(&power_domains->lock);
 }
 
@@ -5782,13 +5792,11 @@ void intel_display_power_put(struct drm_device *dev,
 
 	mutex_lock(&power_domains->lock);
 
-	for_each_power_well_rev(i, power_well, BIT(domain), power_domains)
-		__intel_power_well_put(dev, power_well);
-
-#if IS_ENABLED(CONFIG_DEBUG_FS)
 	WARN_ON(!power_domains->domain_use_count[domain]);
 	power_domains->domain_use_count[domain]--;
-#endif
+
+	for_each_power_well_rev(i, power_well, BIT(domain), power_domains)
+		__intel_power_well_put(dev, power_well);
 
 	mutex_unlock(&power_domains->lock);
 }