[PATCH] drm: Remove dev_pm_ops from drm_class

[Lukas Wunner]

The PM core introduced the ability to keep devices runtime suspended
during the entire system suspend/resume process with commit aae4518b3124
("PM / sleep: Mechanism to avoid resuming runtime-suspended devices
unnecessarily"). Before this so-called "direct-complete" procedure was
introduced, devices were always runtime resumed only to be immediately
put to sleep again using their ->suspend hook. Direct-complete is
enabled by returning a positive value from the ->prepare hook. The PCI
core usually does this automatically.

Direct-complete is only available for a device if all children use it as
well. Currently we cannot support direct-complete for DRM drivers
because the DRM core automatically registers multiple DRM minors which
belong to device class drm_class, and drm_class uses a struct dev_pm_ops
which lacks the ->prepare callback.

While this could be solved by adding the missing ->prepare callback,
closer inspection shows that there are no DRM drivers left which declare
the legacy ->suspend and ->resume callbacks in their drm_driver struct.
The last ones to remove them were i915 with commit 1751fcf9f92e
("drm/i915: Fix module initialisation, v2.") and exynos with commit
e7fefb1d5af5 ("drm/exynos: remove legacy ->suspend()/resume()").

Consequently the struct dev_pm_ops of drm_class is now dead code. Remove
it. If no dev_pm_ops is declared for a device, the PM core automatically
enables direct-complete for it, thereby making that mechanism available
to the parent DRM PCI devices.

Signed-off-by: Lukas Wunner <lukas at wunner.de>
---
 drivers/gpu/drm/drm_drv.c   |  2 --
 drivers/gpu/drm/drm_sysfs.c | 71 ---------------------------------------------
 include/drm/drmP.h          |  2 --
 3 files changed, 75 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index bff8922..8b2582a 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -605,8 +605,6 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver,
 		ret = drm_minor_alloc(dev, DRM_MINOR_CONTROL);
 		if (ret)
 			goto err_minors;
-
-		WARN_ON(driver->suspend || driver->resume);
 	}
 
 	if (drm_core_check_feature(dev, DRIVER_RENDER)) {
diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index fa7fadc..32dd821 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -32,75 +32,6 @@ static struct device_type drm_sysfs_device_minor = {
 
 struct class *drm_class;
 
-/**
- * __drm_class_suspend - internal DRM class suspend routine
- * @dev: Linux device to suspend
- * @state: power state to enter
- *
- * Just figures out what the actual struct drm_device associated with
- * @dev is and calls its suspend hook, if present.
- */
-static int __drm_class_suspend(struct device *dev, pm_message_t state)
-{
-	if (dev->type == &drm_sysfs_device_minor) {
-		struct drm_minor *drm_minor = to_drm_minor(dev);
-		struct drm_device *drm_dev = drm_minor->dev;
-
-		if (drm_minor->type == DRM_MINOR_LEGACY &&
-		    !drm_core_check_feature(drm_dev, DRIVER_MODESET) &&
-		    drm_dev->driver->suspend)
-			return drm_dev->driver->suspend(drm_dev, state);
-	}
-	return 0;
-}
-
-/**
- * drm_class_suspend - internal DRM class suspend hook. Simply calls
- * __drm_class_suspend() with the correct pm state.
- * @dev: Linux device to suspend
- */
-static int drm_class_suspend(struct device *dev)
-{
-	return __drm_class_suspend(dev, PMSG_SUSPEND);
-}
-
-/**
- * drm_class_freeze - internal DRM class freeze hook. Simply calls
- * __drm_class_suspend() with the correct pm state.
- * @dev: Linux device to freeze
- */
-static int drm_class_freeze(struct device *dev)
-{
-	return __drm_class_suspend(dev, PMSG_FREEZE);
-}
-
-/**
- * drm_class_resume - DRM class resume hook
- * @dev: Linux device to resume
- *
- * Just figures out what the actual struct drm_device associated with
- * @dev is and calls its resume hook, if present.
- */
-static int drm_class_resume(struct device *dev)
-{
-	if (dev->type == &drm_sysfs_device_minor) {
-		struct drm_minor *drm_minor = to_drm_minor(dev);
-		struct drm_device *drm_dev = drm_minor->dev;
-
-		if (drm_minor->type == DRM_MINOR_LEGACY &&
-		    !drm_core_check_feature(drm_dev, DRIVER_MODESET) &&
-		    drm_dev->driver->resume)
-			return drm_dev->driver->resume(drm_dev);
-	}
-	return 0;
-}
-
-static const struct dev_pm_ops drm_class_dev_pm_ops = {
-	.suspend	= drm_class_suspend,
-	.resume		= drm_class_resume,
-	.freeze		= drm_class_freeze,
-};
-
 static char *drm_devnode(struct device *dev, umode_t *mode)
 {
 	return kasprintf(GFP_KERNEL, "dri/%s", dev_name(dev));
@@ -131,8 +62,6 @@ int drm_sysfs_init(void)
 	if (IS_ERR(drm_class))
 		return PTR_ERR(drm_class);
 
-	drm_class->pm = &drm_class_dev_pm_ops;
-
 	err = class_create_file(drm_class, &class_attr_version.attr);
 	if (err) {
 		class_destroy(drm_class);
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index c5d2950..fc40543 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -416,8 +416,6 @@ struct drm_driver {
 	void (*postclose) (struct drm_device *, struct drm_file *);
 	void (*lastclose) (struct drm_device *);
 	int (*unload) (struct drm_device *);
-	int (*suspend) (struct drm_device *, pm_message_t state);
-	int (*resume) (struct drm_device *);
 	int (*dma_ioctl) (struct drm_device *dev, void *data, struct drm_file *file_priv);
 	int (*dma_quiescent) (struct drm_device *);
 	int (*context_dtor) (struct drm_device *dev, int context);
-- 
2.8.1