[PATCH 09/27] drm/atomic-helper: roll out commit synchronization
Maarten Lankhorst
maarten.lankhorst at linux.intel.com
Thu Jun 9 14:22:05 UTC 2016
Op 08-06-16 om 14:19 schreef Daniel Vetter:
> To facilitate easier reviewing this is split out from the overall
> nonblocking commit rework. It just rolls out the helper functions
> and uses them in the main drm_atomic_helper_commit() function
> to make it clear where in the flow they're used.
>
> The next patch will actually split drm_atomic_helper_commit() into
> 2 pieces, with the tail being run asynchronously from a worker.
>
> v2: Improve kerneldocs (Maarten).
>
> v3: Don't convert ERESTARTSYS to EINTR (Maarten). Also don't fail if
> the wait succeed in stall_check - we need to convert that case (it
> returns the remaining jiffies) to 0 for success.
>
> Tested-by: Tomeu Vizoso <tomeu.vizoso at collabora.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Tomeu Vizoso <tomeu.vizoso at gmail.com>
> Cc: Daniel Stone <daniels at collabora.com>
> Tested-by: Liviu Dudau <Liviu.Dudau at arm.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 346 ++++++++++++++++++++++++++++++++++++
> include/drm/drm_atomic_helper.h | 7 +
> 2 files changed, 353 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 326ee34cdba4..63e46827b303 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1155,6 +1155,10 @@ int drm_atomic_helper_commit(struct drm_device *dev,
> if (nonblock)
> return -EBUSY;
>
> + ret = drm_atomic_helper_setup_commit(state, nonblock);
> + if (ret)
> + return ret;
> +
> ret = drm_atomic_helper_prepare_planes(dev, state);
> if (ret)
> return ret;
> @@ -1185,16 +1189,22 @@ int drm_atomic_helper_commit(struct drm_device *dev,
>
> drm_atomic_helper_wait_for_fences(dev, state);
>
> + drm_atomic_helper_wait_for_dependencies(state);
> +
> drm_atomic_helper_commit_modeset_disables(dev, state);
>
> drm_atomic_helper_commit_planes(dev, state, false);
>
> drm_atomic_helper_commit_modeset_enables(dev, state);
>
> + drm_atomic_helper_commit_hw_done(state);
> +
> drm_atomic_helper_wait_for_vblanks(dev, state);
>
> drm_atomic_helper_cleanup_planes(dev, state);
>
> + drm_atomic_helper_commit_cleanup_done(state);
> +
> drm_atomic_state_free(state);
>
> return 0;
> @@ -1239,6 +1249,305 @@ EXPORT_SYMBOL(drm_atomic_helper_commit);
> * being displayed.
> */
>
> +static int stall_checks(struct drm_crtc *crtc, bool nonblock)
> +{
> + struct drm_crtc_commit *commit, *stall_commit = NULL;
> + bool completed = true;
> + int i, ret = 0;
> +
> + spin_lock(&crtc->commit_lock);
> + i = 0;
> + list_for_each_entry(commit, &crtc->commit_list, commit_entry) {
> + if (i == 0) {
> + completed = try_wait_for_completion(&commit->flip_done);
> + /* Userspace is not allowed to get ahead of the previous
> + * commit with nonblocking ones. */
> + if (!completed && nonblock) {
> + spin_unlock(&crtc->commit_lock);
> + return -EBUSY;
> + }
> + } else if (i == 1) {
> + stall_commit = commit;
> + drm_crtc_commit_get(stall_commit);
> + } else
> + break;
> +
> + i++;
> + }
> + spin_unlock(&crtc->commit_lock);
> +
> + if (!stall_commit)
> + return 0;
> +
> + /* We don't want to let commits get ahead of cleanup work too much,
> + * stalling on 2nd previous commit means triple-buffer won't ever stall.
> + */
> + ret = wait_for_completion_interruptible_timeout(&commit->cleanup_done,
> + 10*HZ);
> + if (ret == 0)
> + DRM_ERROR("[CRTC:%d:%s] cleanup_done timed out\n",
> + crtc->base.id, crtc->name);
> +
> + drm_crtc_commit_put(stall_commit);
> +
> + return ret < 0 ? ret : 0;
> +}
> +
> +/**
> + * drm_atomic_helper_setup_commit - setup possibly nonblocking commit
> + * @state: new modeset state to be committed
> + * @nonblock: whether nonblocking behavior is requested.
> + *
> + * This function prepares @state to be used by the atomic helper's support for
> + * nonblocking commits. Drivers using the nonblocking commit infrastructure
> + * should always call this function from their ->atomic_commit hook.
> + *
> + * To be able to use this support drivers need to use a few more helper
> + * functions. drm_atomic_helper_wait_for_dependencies() must be called before
> + * actually committing the hardware state, and for nonblocking commits this call
> + * must be placed in the async worker. See also drm_atomic_helper_swap_state()
> + * and it's stall parameter, for when a driver's commit hooks look at the
> + * ->state pointers of struct &drm_crtc, &drm_plane or &drm_connector directly.
> + *
> + * Completion of the hardware commit step must be signalled using
> + * drm_atomic_helper_commit_hw_done(). After this step the driver is not allowed
> + * to read or change any permanent software or hardware modeset state. The only
> + * exception is state protected by other means than &drm_modeset_lock locks.
> + * Only the free standing @state with pointers to the old state structures can
> + * be inspected, e.g. to clean up old buffers using
> + * drm_atomic_helper_cleanup_planes().
> + *
> + * At the very end, before cleaning up @state drivers must call
> + * drm_atomic_helper_commit_cleanup_done().
> + *
> + * This is all implemented by in drm_atomic_helper_commit(), giving drivers a
> + * complete and esay-to-use default implementation of the atomic_commit() hook.
> + *
> + * The tracking of asynchronously executed and still pending commits is done
> + * using the core structure &drm_crtc_commit.
> + *
> + * By default there's no need to clean up resources allocated by this function
> + * explicitly: drm_atomic_state_default_clear() will take care of that
> + * automatically.
> + *
> + * Returns:
> + *
> + * 0 on success. -EBUSY when userspace schedules nonblocking commits too fast,
> + * -ENOMEM on allocation failures and -EINTR when a signal is pending.
> + */
> +int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
> + bool nonblock)
> +{
> + struct drm_crtc *crtc;
> + struct drm_crtc_state *crtc_state;
> + struct drm_crtc_commit *commit;
> + int i, ret;
> +
> + for_each_crtc_in_state(state, crtc, crtc_state, i) {
> + commit = kzalloc(sizeof(*commit), GFP_KERNEL);
> + if (!commit)
> + return -ENOMEM;
> +
> + init_completion(&commit->flip_done);
> + init_completion(&commit->hw_done);
> + init_completion(&commit->cleanup_done);
> + INIT_LIST_HEAD(&commit->commit_entry);
> + kref_init(&commit->ref);
> + commit->crtc = crtc;
> +
> + state->crtcs[i].commit = commit;
> +
> + ret = stall_checks(crtc, nonblock);
> + if (ret)
> + return ret;
> +
> + /* Drivers only send out events when at least either current or
> + * new CRTC state is active. Complete right away if everything
> + * stays off. */
> + if (!crtc->state->active && !crtc_state->active) {
> + complete_all(&commit->flip_done);
> + continue;
> + }
> +
> + /* Legacy cursor updates are fully unsynced. */
> + if (state->legacy_cursor_update) {
> + complete_all(&commit->flip_done);
> + continue;
> + }
> +
> + if (!crtc_state->event) {
> + commit->event = kzalloc(sizeof(*commit->event),
> + GFP_KERNEL);
> + if (!commit->event)
> + return -ENOMEM;
> +
> + crtc_state->event = commit->event;
> + }
> +
> + crtc_state->event->base.completion = &commit->flip_done;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_setup_commit);
> +
> +
> +static struct drm_crtc_commit *preceeding_commit(struct drm_crtc *crtc)
> +{
> + struct drm_crtc_commit *commit;
> + int i = 0;
> +
> + list_for_each_entry(commit, &crtc->commit_list, commit_entry) {
> + /* skip the first entry, that's the current commit */
> + if (i == 1)
> + return commit;
> + i++;
> + }
> +
> + return NULL;
> +}
> +
> +/**
> + * drm_atomic_helper_wait_for_dependencies - wait for required preceeding commits
> + * @state: new modeset state to be committed
> + *
> + * This function waits for all preceeding commits that touch the same CRTC as
> + * @state to both be committed to the hardware (as signalled by
> + * drm_atomic_Helper_commit_hw_done) and executed by the hardware (as signalled
^extra cap here
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