drm/i915: add dev_to_i915 helper

This will be needed by later patches, so factor it out.

No functional change.

v2:
- s/dev_to_i915_priv/dev_to_i915/ (Jani)
- don't use the helper in i915_pm_suspend (Chris)
- simplify the helper (Chris)
v3:
- remove redundant upcasting in the helper (Daniel)

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -940,8 +940,7 @@ static int i915_pm_suspend(struct device *dev)
 
 static int i915_pm_suspend_late(struct device *dev)
 {
-	struct pci_dev *pdev = to_pci_dev(dev);
-	struct drm_device *drm_dev = pci_get_drvdata(pdev);
+	struct drm_device *drm_dev = dev_to_i915(dev)->dev;
 
 	/*
 	 * We have a suspedn ordering issue with the snd-hda driver also
@@ -960,8 +959,7 @@ static int i915_pm_suspend_late(struct device *dev)
 
 static int i915_pm_resume_early(struct device *dev)
 {
-	struct pci_dev *pdev = to_pci_dev(dev);
-	struct drm_device *drm_dev = pci_get_drvdata(pdev);
+	struct drm_device *drm_dev = dev_to_i915(dev)->dev;
 
 	if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF)
 		return 0;
@@ -971,8 +969,7 @@ static int i915_pm_resume_early(struct device *dev)
 
 static int i915_pm_resume(struct device *dev)
 {
-	struct pci_dev *pdev = to_pci_dev(dev);
-	struct drm_device *drm_dev = pci_get_drvdata(pdev);
+	struct drm_device *drm_dev = dev_to_i915(dev)->dev;
 
 	if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF)
 		return 0;

drivers/gpu/drm/i915/i915_drv.h

@@ -1781,6 +1781,11 @@ static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
 	return dev->dev_private;
 }
 
+static inline struct drm_i915_private *dev_to_i915(struct device *dev)
+{
+	return to_i915(dev_get_drvdata(dev));
+}
+
 /* Iterate over initialised rings */
 #define for_each_ring(ring__, dev_priv__, i__) \
 	for ((i__) = 0; (i__) < I915_NUM_RINGS; (i__)++) \