drm/i915: re-init modeset hw state after gpu reset

After a gpu reset we need to re-init some of the hw state we only
initialize when modeset is enabled, like rc6, hw contexts or render/GT
core clock gating and workaround register settings.

Note that this patch has a small change in the resume code:
- rc6 on gen6+ is only restored for the modeset case (for more
  consistency with other callsites). This is no problem because recent
  kernels refuse to load drm/i915 without kms on gen6+
- rc6/emon on ilk is only restored for the modeset case. This is no
  problem because rc6 is disabled by default on ilk, and ums on ilk
  has never really been a supported option outside of horrible rhel
  backports.

v2: Chris Wilson noticed that we not only fail to restore the clock
gating settings after gpu reset.

v3: Move the call to modeset_init_hw in _reset out of the
struct_mutext protected area - other callers don't hold it, too.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -851,9 +851,14 @@ int i915_reset(struct drm_device *dev, u8 flags)
 		i915_gem_init_ppgtt(dev);
 
 		mutex_unlock(&dev->struct_mutex);
+
+		if (drm_core_check_feature(dev, DRIVER_MODESET))
+			intel_modeset_init_hw(dev);
+
 		drm_irq_uninstall(dev);
 		drm_mode_config_reset(dev);
 		drm_irq_install(dev);
+
 		mutex_lock(&dev->struct_mutex);
 	}
 

drivers/gpu/drm/i915/i915_drv.h

@@ -1433,6 +1433,7 @@ static inline void intel_unregister_dsm_handler(void) { return; }
 #endif /* CONFIG_ACPI */
 
 /* modesetting */
+extern void intel_modeset_init_hw(struct drm_device *dev);
 extern void intel_modeset_init(struct drm_device *dev);
 extern void intel_modeset_gem_init(struct drm_device *dev);
 extern void intel_modeset_cleanup(struct drm_device *dev);

drivers/gpu/drm/i915/i915_suspend.c

@@ -879,17 +879,7 @@ int i915_restore_state(struct drm_device *dev)
 	mutex_unlock(&dev->struct_mutex);
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET))
-		intel_init_clock_gating(dev);
-
-	if (IS_IRONLAKE_M(dev)) {
-		ironlake_enable_drps(dev);
-		intel_init_emon(dev);
-	}
-
-	if (INTEL_INFO(dev)->gen >= 6) {
-		gen6_enable_rps(dev_priv);
-		gen6_update_ring_freq(dev_priv);
-	}
+		intel_modeset_init_hw(dev);
 
 	mutex_lock(&dev->struct_mutex);
 

drivers/gpu/drm/i915/intel_display.c

@@ -9530,6 +9530,23 @@ static void i915_disable_vga(struct drm_device *dev)
 	POSTING_READ(vga_reg);
 }
 
+void intel_modeset_init_hw(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	intel_init_clock_gating(dev);
+
+	if (IS_IRONLAKE_M(dev)) {
+		ironlake_enable_drps(dev);
+		intel_init_emon(dev);
+	}
+
+	if (IS_GEN6(dev) || IS_GEN7(dev)) {
+		gen6_enable_rps(dev_priv);
+		gen6_update_ring_freq(dev_priv);
+	}
+}
+
 void intel_modeset_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -9575,17 +9592,7 @@ void intel_modeset_init(struct drm_device *dev)
 	i915_disable_vga(dev);
 	intel_setup_outputs(dev);
 
-	intel_init_clock_gating(dev);
-
-	if (IS_IRONLAKE_M(dev)) {
-		ironlake_enable_drps(dev);
-		intel_init_emon(dev);
-	}
-
-	if (IS_GEN6(dev) || IS_GEN7(dev)) {
-		gen6_enable_rps(dev_priv);
-		gen6_update_ring_freq(dev_priv);
-	}
+	intel_modeset_init_hw(dev);
 
 	INIT_WORK(&dev_priv->idle_work, intel_idle_update);
 	setup_timer(&dev_priv->idle_timer, intel_gpu_idle_timer,