drm/i915: Periodically sanity check power management

Every time we use the device after a period of idleness, check that the
power management setup is still sane. This is to workaround a bug
whereby it seems that we begin suppressing power management interrupts,
preventing SandyBridge+ from going into turbo mode.

This patch does have a side-effect. It removes the mark-busy for just
moving the cursor - we don't want to increase the render clock just for
the sprite, though we may want to bump the display frequency. I'd argue
that we do not, and certainly don't want to take the struct_mutex here
due to the large latencies that introduces.

References: https://bugs.freedesktop.org/show_bug.cgi?id=44006
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -240,6 +240,7 @@ struct drm_i915_display_funcs {
 	void (*update_wm)(struct drm_device *dev);
 	void (*update_sprite_wm)(struct drm_device *dev, int pipe,
 				 uint32_t sprite_width, int pixel_size);
+	void (*sanitize_pm)(struct drm_device *dev);
 	int (*crtc_mode_set)(struct drm_crtc *crtc,
 			     struct drm_display_mode *mode,
 			     struct drm_display_mode *adjusted_mode,

drivers/gpu/drm/i915/intel_display.c

@@ -4834,9 +4834,6 @@ static void intel_crtc_update_cursor(struct drm_crtc *crtc,
 		else
 			i9xx_update_cursor(crtc, base);
 	}
-
-	if (visible)
-		intel_mark_busy(dev, to_intel_framebuffer(crtc->fb)->obj);
 }
 
 static int intel_crtc_cursor_set(struct drm_crtc *crtc,
@@ -5530,9 +5527,10 @@ void intel_mark_busy(struct drm_device *dev, struct drm_i915_gem_object *obj)
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		return;
 
-	if (!dev_priv->busy)
+	if (!dev_priv->busy) {
+		intel_sanitize_pm(dev);
 		dev_priv->busy = true;
-	else
+	} else
 		mod_timer(&dev_priv->idle_timer, jiffies +
 			  msecs_to_jiffies(GPU_IDLE_TIMEOUT));
 

drivers/gpu/drm/i915/intel_drv.h

@@ -344,6 +344,8 @@ extern int intel_plane_init(struct drm_device *dev, enum pipe pipe);
 extern void intel_flush_display_plane(struct drm_i915_private *dev_priv,
 				      enum plane plane);
 
+void intel_sanitize_pm(struct drm_device *dev);
+
 /* intel_panel.c */
 extern void intel_fixed_panel_mode(struct drm_display_mode *fixed_mode,
 				   struct drm_display_mode *adjusted_mode);

drivers/gpu/drm/i915/intel_pm.c

@@ -3525,6 +3525,41 @@ void intel_init_clock_gating(struct drm_device *dev)
 		dev_priv->display.init_pch_clock_gating(dev);
 }
 
+static void gen6_sanitize_pm(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	u32 limits, delay, old;
+
+	gen6_gt_force_wake_get(dev_priv);
+
+	old = limits = I915_READ(GEN6_RP_INTERRUPT_LIMITS);
+	/* Make sure we continue to get interrupts
+	 * until we hit the minimum or maximum frequencies.
+	 */
+	limits &= ~(0x3f << 16 | 0x3f << 24);
+	delay = dev_priv->cur_delay;
+	if (delay < dev_priv->max_delay)
+		limits |= (dev_priv->max_delay & 0x3f) << 24;
+	if (delay > dev_priv->min_delay)
+		limits |= (dev_priv->min_delay & 0x3f) << 16;
+
+	if (old != limits) {
+		DRM_ERROR("Power management discrepancy: GEN6_RP_INTERRUPT_LIMITS expected %08x, was %08x\n",
+			  limits, old);
+		I915_WRITE(GEN6_RP_INTERRUPT_LIMITS, limits);
+	}
+
+	gen6_gt_force_wake_put(dev_priv);
+}
+
+void intel_sanitize_pm(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (dev_priv->display.sanitize_pm)
+		dev_priv->display.sanitize_pm(dev);
+}
+
 /* Set up chip specific power management-related functions */
 void intel_init_pm(struct drm_device *dev)
 {
@@ -3607,6 +3642,7 @@ void intel_init_pm(struct drm_device *dev)
 				dev_priv->display.update_wm = NULL;
 			}
 			dev_priv->display.init_clock_gating = gen6_init_clock_gating;
+			dev_priv->display.sanitize_pm = gen6_sanitize_pm;
 		} else if (IS_IVYBRIDGE(dev)) {
 			/* FIXME: detect B0+ stepping and use auto training */
 			if (SNB_READ_WM0_LATENCY()) {
@@ -3618,6 +3654,7 @@ void intel_init_pm(struct drm_device *dev)
 				dev_priv->display.update_wm = NULL;
 			}
 			dev_priv->display.init_clock_gating = ivybridge_init_clock_gating;
+			dev_priv->display.sanitize_pm = gen6_sanitize_pm;
 		} else
 			dev_priv->display.update_wm = NULL;
 	} else if (IS_VALLEYVIEW(dev)) {