[PATCH 1/2] drm: introduce page_flip_timeout()

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

There should be a mechanism for drivers to respond to flip_done
time outs. Since, as it stands it is possible for the display
to stall indefinitely, necessitating a hard reset. So, introduce
a new crtc callback that is called by
drm_atomic_helper_wait_for_flip_done() to give drivers a shot
at recovering from page flip timeouts.

Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 6 +++++-
 include/drm/drm_crtc.h              | 9 +++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 5840e9cc6f66..3a144c324b19 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1881,9 +1881,13 @@ void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
 			continue;
 
 		ret = wait_for_completion_timeout(&commit->flip_done, 10 * HZ);
-		if (ret == 0)
+		if (!ret) {
 			drm_err(dev, "[CRTC:%d:%s] flip_done timed out\n",
 				crtc->base.id, crtc->name);
+
+			if (crtc->funcs->page_flip_timeout)
+				crtc->funcs->page_flip_timeout(crtc);
+		}
 	}
 
 	if (state->fake_commit)
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 66278ffeebd6..45dc5a76e915 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -609,6 +609,15 @@ struct drm_crtc_funcs {
 				uint32_t flags, uint32_t target,
 				struct drm_modeset_acquire_ctx *ctx);
 
+	/**
+	 * @page_flip_timeout:
+	 *
+	 * This optional hook is called if &drm_crtc_commit.flip_done times out,
+	 * and can be used by drivers to attempt to recover from a page flip
+	 * timeout.
+	 */
+	void (*page_flip_timeout)(struct drm_crtc *crtc);
+
 	/**
 	 * @set_property:
 	 *
-- 
2.52.0