drm/i915: HSW: allow PCH clock gating for suspend

For the device to enter D3 we should enable PCH clock gating.

v2:
- use HAS_PCH_LPT instead of IS_HASWELL (Ville, Paolo)
- rename lpt_allow_clock_gating to lpt_suspend_hw (Paolo)

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.c

@@ -529,6 +529,8 @@ static int i915_drm_freeze(struct drm_device *dev)
 		 */
 		list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
 			dev_priv->display.crtc_disable(crtc);
+
+		intel_modeset_suspend_hw(dev);
 	}
 
 	i915_save_state(dev);

drivers/gpu/drm/i915/i915_drv.h

@@ -1865,6 +1865,7 @@ static inline void intel_unregister_dsm_handler(void) { return; }
 
 /* modesetting */
 extern void intel_modeset_init_hw(struct drm_device *dev);
+extern void intel_modeset_suspend_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/intel_display.c

@@ -9271,6 +9271,11 @@ void intel_modeset_init_hw(struct drm_device *dev)
 	mutex_unlock(&dev->struct_mutex);
 }
 
+void intel_modeset_suspend_hw(struct drm_device *dev)
+{
+	intel_suspend_hw(dev);
+}
+
 void intel_modeset_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;

drivers/gpu/drm/i915/intel_drv.h

@@ -716,6 +716,7 @@ extern void assert_pipe(struct drm_i915_private *dev_priv, enum pipe pipe,
 #define assert_pipe_disabled(d, p) assert_pipe(d, p, false)
 
 extern void intel_init_clock_gating(struct drm_device *dev);
+extern void intel_suspend_hw(struct drm_device *dev);
 extern void intel_write_eld(struct drm_encoder *encoder,
 			    struct drm_display_mode *mode);
 extern void intel_prepare_ddi(struct drm_device *dev);

drivers/gpu/drm/i915/intel_pm.c

@@ -3988,6 +3988,18 @@ static void lpt_init_clock_gating(struct drm_device *dev)
 			   PCH_LP_PARTITION_LEVEL_DISABLE);
 }
 
+static void lpt_suspend_hw(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
+	if (dev_priv->pch_id == INTEL_PCH_LPT_LP_DEVICE_ID_TYPE) {
+		uint32_t val = I915_READ(SOUTH_DSPCLK_GATE_D);
+
+		val &= ~PCH_LP_PARTITION_LEVEL_DISABLE;
+		I915_WRITE(SOUTH_DSPCLK_GATE_D, val);
+	}
+}
+
 static void haswell_init_clock_gating(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -4340,6 +4352,12 @@ void intel_init_clock_gating(struct drm_device *dev)
 	dev_priv->display.init_clock_gating(dev);
 }
 
+void intel_suspend_hw(struct drm_device *dev)
+{
+	if (HAS_PCH_LPT(dev))
+		lpt_suspend_hw(dev);
+}
+
 /**
  * We should only use the power well if we explicitly asked the hardware to
  * enable it, so check if it's enabled and also check if we've requested it to