Re: [PATCH v3 1/2] drm: introduce KMS recovery mechanism

Mario Limonciello
2026-02-13T00:18:31Z

On 2/12/2026 5:08 PM, Hamza Mahfooz wrote:
> 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()).

Since you were able to (relatively) reliably reproduce a problem in
amdgpu, how far in your iterative flow did you get? Did you manage to
need the vendor specific handling? And presumably that helped?

>
> 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.
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 45 +++++++++++++++++++++++++----
> include/drm/drm_atomic_helper.h | 4 +--
> include/drm/drm_device.h | 24 +++++++++++++++
> 3 files changed, 66 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 5840e9cc6f66..6ae1234b9e20 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>
> @@ -1864,11 +1865,15 @@ 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++) {
> @@ -1881,13 +1886,43 @@ 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)
> - drm_err(dev, "[CRTC:%d:%s] flip_done timed out\n",
> - crtc->base.id, crtc->name);
> + if (!ret) {
> + 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;

Since you're iterating multiple CRTCs if you manage to recover from one
with this call shouldn't you keep iterating the rest?

> + 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);