drm: Don't test for IRQ support in VBLANK ioctls

For KMS drivers, replace the IRQ check in VBLANK ioctls with a check for
vblank support. IRQs might be enabled wthout vblanking being supported.

This change also removes the DRM framework's only dependency on IRQ state
for non-legacy drivers. For legacy drivers with userspace modesetting,
the original test remains in drm_wait_vblank_ioctl().

v4:
	* avoid preprocessor ifdef in drm_wait_vblank_ioctl()
	  (Jani, Thierry)
v3:
	* optimize test in drm_wait_vblank_ioctl() for KMS case (Liviu)
	* update docs for drm_irq_uninstall()
v2:
	* keep the old test for legacy drivers in
	  drm_wait_vblank_ioctl() (Daniel)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210625082222.3845-5-tzimmermann@suse.de

drivers/gpu/drm/drm_irq.c

@@ -74,10 +74,8 @@
  * only supports devices with a single interrupt on the main device stored in
  * &drm_device.dev and set as the device paramter in drm_dev_alloc().
  *
- * These IRQ helpers are strictly optional. Drivers which roll their own only
- * need to set &drm_device.irq_enabled to signal the DRM core that vblank
- * interrupts are working. Since these helpers don't automatically clean up the
- * requested interrupt like e.g. devm_request_irq() they're not really
+ * These IRQ helpers are strictly optional. Since these helpers don't automatically
+ * clean up the requested interrupt like e.g. devm_request_irq() they're not really
  * recommended.
  */
 
@@ -91,9 +89,7 @@
  * and after the installation.
  *
  * This is the simplified helper interface provided for drivers with no special
- * needs. Drivers which need to install interrupt handlers for multiple
- * interrupts must instead set &drm_device.irq_enabled to signal the DRM core
- * that vblank interrupts are available.
+ * needs.
  *
  * @irq must match the interrupt number that would be passed to request_irq(),
  * if called directly instead of using this helper function.
@@ -156,8 +152,7 @@ EXPORT_SYMBOL(drm_irq_install);
  *
  * Calls the driver's &drm_driver.irq_uninstall function and unregisters the IRQ
  * handler.  This should only be called by drivers which used drm_irq_install()
- * to set up their interrupt handler. Other drivers must only reset
- * &drm_device.irq_enabled to false.
+ * to set up their interrupt handler.
  *
  * Note that for kernel modesetting drivers it is a bug if this function fails.
  * The sanity checks are only to catch buggy user modesetting drivers which call

drivers/gpu/drm/drm_vblank.c

@@ -1737,6 +1737,15 @@ static void drm_wait_vblank_reply(struct drm_device *dev, unsigned int pipe,
 	reply->tval_usec = ts.tv_nsec / 1000;
 }
 
+static bool drm_wait_vblank_supported(struct drm_device *dev)
+{
+	if  (IS_ENABLED(CONFIG_DRM_LEGACY)) {
+		if (unlikely(drm_core_check_feature(dev, DRIVER_LEGACY)))
+			return dev->irq_enabled;
+	}
+	return drm_dev_has_vblank(dev);
+}
+
 int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
 			  struct drm_file *file_priv)
 {
@@ -1748,7 +1757,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
 	unsigned int pipe_index;
 	unsigned int flags, pipe, high_pipe;
 
-	if (!dev->irq_enabled)
+	if (!drm_wait_vblank_supported(dev))
 		return -EOPNOTSUPP;
 
 	if (vblwait->request.type & _DRM_VBLANK_SIGNAL)
@@ -2023,7 +2032,7 @@ int drm_crtc_get_sequence_ioctl(struct drm_device *dev, void *data,
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		return -EOPNOTSUPP;
 
-	if (!dev->irq_enabled)
+	if (!drm_dev_has_vblank(dev))
 		return -EOPNOTSUPP;
 
 	crtc = drm_crtc_find(dev, file_priv, get_seq->crtc_id);
@@ -2082,7 +2091,7 @@ int drm_crtc_queue_sequence_ioctl(struct drm_device *dev, void *data,
 	if (!drm_core_check_feature(dev, DRIVER_MODESET))
 		return -EOPNOTSUPP;
 
-	if (!dev->irq_enabled)
+	if (!drm_dev_has_vblank(dev))
 		return -EOPNOTSUPP;
 
 	crtc = drm_crtc_find(dev, file_priv, queue_seq->crtc_id);