[PATCH v4 1/2] drm: introduce KMS recovery mechanism

[Hamza Mahfooz <someguy@effective-light.com>]

There should be a mechanism for drivers to respond to flip_done
timeouts. Since, as it stands it is possible for the display to stall
indefinitely, necessitating a hard reset. So, introduce a new mechanism
that tries various methods of recovery with increasing aggression, in
the following order:

1. Force a full modeset (have the compositor reprogram the state from
   scratch).
2. As a last resort, have the driver attempt a vendor specific reset
   (which they can do by reading the return value of
   drm_atomic_helper_wait_for_flip_done()).

Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
---
v2: new to the series
v3: get rid of page_flip_timeout() and have
    drm_atomic_helper_wait_for_flip_done() return a error.
v4: get rid of nested ret variable.
---
 drivers/gpu/drm/drm_atomic_helper.c | 47 ++++++++++++++++++++++++-----
 include/drm/drm_atomic_helper.h     |  4 +--
 include/drm/drm_device.h            | 24 +++++++++++++++
 3 files changed, 66 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 5840e9cc6f66..d905eb166225 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -42,6 +42,7 @@
 #include <drm/drm_gem_atomic_helper.h>
 #include <drm/drm_panic.h>
 #include <drm/drm_print.h>
+#include <drm/drm_probe_helper.h>
 #include <drm/drm_self_refresh_helper.h>
 #include <drm/drm_vblank.h>
 #include <drm/drm_writeback.h>
@@ -1864,30 +1865,62 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_vblanks);
  *
  * This requires that drivers use the nonblocking commit tracking support
  * initialized using drm_atomic_helper_setup_commit().
+ *
+ * Returns:
+ * -ETIMEDOUT to indicate that drivers can attempt a vendor reset, 0 otherwise.
  */
-void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
-					  struct drm_atomic_state *state)
+int drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
+					 struct drm_atomic_state *state)
 {
 	struct drm_crtc *crtc;
+	int ret = 0;
 	int i;
 
 	for (i = 0; i < dev->mode_config.num_crtc; i++) {
 		struct drm_crtc_commit *commit = state->crtcs[i].commit;
-		int ret;
 
 		crtc = state->crtcs[i].ptr;
 
 		if (!crtc || !commit)
 			continue;
 
-		ret = wait_for_completion_timeout(&commit->flip_done, 10 * HZ);
-		if (ret == 0)
-			drm_err(dev, "[CRTC:%d:%s] flip_done timed out\n",
-				crtc->base.id, crtc->name);
+		if (!wait_for_completion_timeout(&commit->flip_done, 10 * HZ)) {
+			switch (dev->reset_phase) {
+			case DRM_KMS_RESET_NONE:
+				drm_err(dev, "[CRTC:%d:%s] flip_done timed out\n",
+					crtc->base.id, crtc->name);
+				dev->reset_phase = DRM_KMS_RESET_FORCE_MODESET;
+				drm_kms_helper_hotplug_event(dev);
+				break;
+			case DRM_KMS_RESET_FORCE_MODESET:
+				drm_err(dev, "[CRTC:%d:%s] force full modeset failed\n",
+					crtc->base.id, crtc->name);
+				dev->reset_phase = DRM_KMS_RESET_VENDOR;
+				ret = -ETIMEDOUT;
+				break;
+			case DRM_KMS_RESET_VENDOR:
+				drm_err(dev, "[CRTC:%d:%s] KMS recovery failed!\n",
+					crtc->base.id, crtc->name);
+				dev->reset_phase = DRM_KMS_RESET_GIVE_UP;
+				break;
+			default:
+				break;
+			}
+
+			goto exit;
+		}
+	}
+
+	if (dev->reset_phase) {
+		drm_info(dev, "KMS recovery succeeded!\n");
+		dev->reset_phase = DRM_KMS_RESET_NONE;
 	}
 
+exit:
 	if (state->fake_commit)
 		complete_all(&state->fake_commit->flip_done);
+
+	return ret;
 }
 EXPORT_SYMBOL(drm_atomic_helper_wait_for_flip_done);
 
diff --git a/include/drm/drm_atomic_helper.h b/include/drm/drm_atomic_helper.h
index 53382fe93537..298c8dff3993 100644
--- a/include/drm/drm_atomic_helper.h
+++ b/include/drm/drm_atomic_helper.h
@@ -79,8 +79,8 @@ int drm_atomic_helper_wait_for_fences(struct drm_device *dev,
 void drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
 					struct drm_atomic_state *old_state);
 
-void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
-					  struct drm_atomic_state *old_state);
+int drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
+					 struct drm_atomic_state *old_state);
 
 void
 drm_atomic_helper_update_legacy_modeset_state(struct drm_device *dev,
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index bc78fb77cc27..1244d7527e7b 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -66,6 +66,23 @@ enum switch_power_state {
 	DRM_SWITCH_POWER_DYNAMIC_OFF = 3,
 };
 
+/**
+ * enum drm_kms_reset_phase - reset phase of drm device
+ */
+enum drm_kms_reset_phase {
+	/** @DRM_KMS_RESET_NONE: Not currently attempting recovery */
+	DRM_KMS_RESET_NONE,
+
+	/** @DRM_KMS_RESET_FORCE_MODESET: Force a full modeset */
+	DRM_KMS_RESET_FORCE_MODESET,
+
+	/** @DRM_KMS_RESET_VENDOR: Attempt a vendor reset */
+	DRM_KMS_RESET_VENDOR,
+
+	/** @DRM_KMS_RESET_GIVE_UP: All recovery methods failed */
+	DRM_KMS_RESET_GIVE_UP,
+};
+
 /**
  * struct drm_device - DRM device structure
  *
@@ -375,6 +392,13 @@ struct drm_device {
 	 * Root directory for debugfs files.
 	 */
 	struct dentry *debugfs_root;
+
+	/**
+	 * @reset_phase:
+	 *
+	 * Reset phase that the device is in.
+	 */
+	enum drm_kms_reset_phase reset_phase;
 };
 
 void drm_dev_set_dma_dev(struct drm_device *dev, struct device *dma_dev);
-- 
2.53.0