Re: [PATCH v5 1/2] drm/atomic: attempt full modeset on page flip timeout

[Mario Limonciello <mario.limonciello@amd.com>]

On 5/1/26 15:35, Hamza Mahfooz wrote:
> We should try to recover from page flip timeouts. Forcing
> a full modeset should be generic across all atomic KMS drivers,
> so try that first.
> 
> Signed-off-by: Hamza Mahfooz <someguy@effective-light.com>
> ---
>   drivers/gpu/drm/drm_atomic_helper.c | 51 +++++++++++++++++++++++++++--
>   1 file changed, 48 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index a768398a1884..8ccc6e833c77 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1926,6 +1926,45 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
>   }
>   EXPORT_SYMBOL(drm_atomic_helper_wait_for_vblanks);
>   
> +static int force_full_modeset(struct drm_crtc *crtc)
> +{
> +	struct drm_modeset_acquire_ctx ctx;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_atomic_state *state;
> +	int ret;
> +	int err;
> +
> +	if (drm_atomic_crtc_needs_modeset(crtc->state))
> +		return -EBUSY;
> +
> +	DRM_MODESET_LOCK_ALL_BEGIN(crtc->dev, ctx, 0, err);
> +	state = drm_atomic_state_alloc(crtc->dev);
> +	if (!state)
> +		return -ENOMEM;
> +
> +	state->acquire_ctx = &ctx;
> +
> +	crtc_state = drm_atomic_get_crtc_state(state, crtc);
> +	if (IS_ERR(crtc_state)) {
> +		ret = PTR_ERR(crtc_state);
> +		goto out;
> +	}
> +
> +	crtc_state->connectors_changed = true;
> +	crtc_state->mode_changed = true;
> +	crtc_state->active_changed = true;

Do you actually need to set all 3 of these to true?

I would think you only need:

crtc_state->mode_changed = true;

> +
> +	drm_info(crtc->dev,
> +		 "[CRTC:%d:%s] Attempting force full modeset...\n",
> +		 crtc->base.id, crtc->name);
> +
> +	ret = drm_atomic_commit(state);
> +out:
> +	drm_atomic_state_put(state);
> +	DRM_MODESET_LOCK_ALL_END(crtc->dev, ctx, err);
> +	return ret;
> +}
> +
>   /**
>    * drm_atomic_helper_wait_for_flip_done - wait for all page flips to be done
>    * @dev: DRM device
> @@ -1949,17 +1988,23 @@ void drm_atomic_helper_wait_for_flip_done(struct drm_device *dev,
>   
>   	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)
> +		if (!wait_for_completion_timeout(&commit->flip_done, 10 * HZ)) {
> +			int ret;
>   			drm_err(dev, "[CRTC:%d:%s] flip_done timed out\n",
>   				crtc->base.id, crtc->name);
> +
> +			ret = force_full_modeset(crtc);
> +			if (ret)
> +				drm_err(dev,
> +					"[CRTC:%d:%s] force full modeset failed! ret=%d\n",
> +					crtc->base.id, crtc->name, ret);
> +		}
>   	}
>   
>   	if (state->fake_commit)