On Wed, Feb 28, 2018 at 08:07:00PM -0800, jsanka@xxxxxxxxxxxxxx wrote:
> On 2018-02-28 11:19, Sean Paul wrote:
> > Moving further towards switching fully to the the atomic helpers, this
> > patch removes the hand-rolled kthread nonblock commit code and uses the
> > atomic helpers commit_work model.
> >
> > There's still a lot of copypasta here, but it's still needed to
> > facilitate the swap_state and prepare_fence private functions. These
> > will be sorted out in a follow-on patch.
> >
> > Change-Id: I9fcba27824ba63d3fab96cb2bc194bfa6f3475b7
> > Signed-off-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/msm/msm_atomic.c | 199 ++++++-------------------------
> > drivers/gpu/drm/msm/msm_drv.c | 1 -
> > drivers/gpu/drm/msm/msm_drv.h | 4 -
> > 3 files changed, 35 insertions(+), 169 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/msm_atomic.c
> > b/drivers/gpu/drm/msm/msm_atomic.c
> > index 3a18bd3dc215..7e54eb65d096 100644
> > --- a/drivers/gpu/drm/msm/msm_atomic.c
> > +++ b/drivers/gpu/drm/msm/msm_atomic.c
> > @@ -21,51 +21,6 @@
> > #include "msm_gem.h"
> > #include "msm_fence.h"
> >
> > -struct msm_commit {
> > - struct drm_device *dev;
> > - struct drm_atomic_state *state;
> > - uint32_t crtc_mask;
> > - bool nonblock;
> > - struct kthread_work commit_work;
> > -};
> > -
> > -/* block until specified crtcs are no longer pending update, and
> > - * atomically mark them as pending update
> > - */
> > -static int start_atomic(struct msm_drm_private *priv, uint32_t
> > crtc_mask)
> > -{
> > - int ret;
> > -
> > - spin_lock(&priv->pending_crtcs_event.lock);
> > - ret = wait_event_interruptible_locked(priv->pending_crtcs_event,
> > - !(priv->pending_crtcs & crtc_mask));
> > - if (ret == 0) {
> > - DBG("start: %08x", crtc_mask);
> > - priv->pending_crtcs |= crtc_mask;
> > - }
> > - spin_unlock(&priv->pending_crtcs_event.lock);
> > -
> > - return ret;
> > -}
> > -
> > -/* clear specified crtcs (no longer pending update)
> > - */
> > -static void end_atomic(struct msm_drm_private *priv, uint32_t
> > crtc_mask)
> > -{
> > - spin_lock(&priv->pending_crtcs_event.lock);
> > - DBG("end: %08x", crtc_mask);
> > - priv->pending_crtcs &= ~crtc_mask;
> > - wake_up_all_locked(&priv->pending_crtcs_event);
> > - spin_unlock(&priv->pending_crtcs_event.lock);
> > -}
> > -
> > -static void commit_destroy(struct msm_commit *c)
> > -{
> > - end_atomic(c->dev->dev_private, c->crtc_mask);
> > - if (c->nonblock)
> > - kfree(c);
> > -}
> > -
> > static void msm_atomic_wait_for_commit_done(
> > struct drm_device *dev,
> > struct drm_atomic_state *old_state)
> > @@ -118,6 +73,10 @@ static void msm_atomic_commit_tail(struct
> > drm_atomic_state *state)
> >
> > msm_atomic_wait_for_commit_done(dev, state);
> >
> > + drm_atomic_helper_commit_hw_done(state);
> > +
> > + drm_atomic_helper_wait_for_vblanks(dev, state);
> > +
> > drm_atomic_helper_cleanup_planes(dev, state);
> >
> > kms->funcs->complete_commit(kms, state);
> > @@ -126,109 +85,25 @@ static void msm_atomic_commit_tail(struct
> > drm_atomic_state *state)
> > /* The (potentially) asynchronous part of the commit. At this point
> > * nothing can fail short of armageddon.
> > */
> > -static void complete_commit(struct msm_commit *c)
> > +static void commit_tail(struct drm_atomic_state *state)
> > {
> > - struct drm_atomic_state *state = c->state;
> > - struct drm_device *dev = state->dev;
> > + drm_atomic_helper_wait_for_fences(state->dev, state, false);
> >
> > - drm_atomic_helper_wait_for_fences(dev, state, false);
> > + drm_atomic_helper_wait_for_dependencies(state);
> >
> > msm_atomic_commit_tail(state);
> >
> > - drm_atomic_state_put(state);
> > -}
> > -
> > -static void _msm_drm_commit_work_cb(struct kthread_work *work)
> > -{
> > - struct msm_commit *commit = NULL;
> > -
> > - if (!work) {
> > - DRM_ERROR("%s: Invalid commit work data!\n", __func__);
> > - return;
> > - }
> > -
> > - commit = container_of(work, struct msm_commit, commit_work);
> > -
> > - complete_commit(commit);
> > -
> > - commit_destroy(commit);
> > -}
> > -
> > -static struct msm_commit *commit_init(struct drm_atomic_state *state,
> > - bool nonblock)
> > -{
> > - struct msm_commit *c = kzalloc(sizeof(*c), GFP_KERNEL);
> > + drm_atomic_helper_commit_cleanup_done(state);
> >
> > - if (!c)
> > - return NULL;
> > -
> > - c->dev = state->dev;
> > - c->state = state;
> > - c->nonblock = nonblock;
> > -
> > - kthread_init_work(&c->commit_work, _msm_drm_commit_work_cb);
> > -
> > - return c;
> > + drm_atomic_state_put(state);
> > }
> >
> > -/* Start display thread function */
> > -static void msm_atomic_commit_dispatch(struct drm_device *dev,
> > - struct drm_atomic_state *state, struct msm_commit *commit)
> > +static void commit_work(struct work_struct *work)
> > {
> > - struct msm_drm_private *priv = dev->dev_private;
> > - struct drm_crtc *crtc = NULL;
> > - struct drm_crtc_state *new_crtc_state = NULL;
> > - int ret = -EINVAL, i = 0, j = 0;
> > - bool nonblock;
> > -
> > - /* cache since work will kfree commit in non-blocking case */
> > - nonblock = commit->nonblock;
> > -
> > - for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
> > - for (j = 0; j < priv->num_crtcs; j++) {
> > - if (priv->disp_thread[j].crtc_id ==
> > - crtc->base.id) {
> > - if (priv->disp_thread[j].thread) {
> > - kthread_queue_work(
> > -
> > &priv->disp_thread[j].worker,
> > -
> > &commit->commit_work);
> Are there any known proposals floating around to support ASYNC commits for
> concurrent displays rendering at different FPS? The above kthread model is
> introduced when we faced some performance road blockers when a display has
> to wait for an ongoing display commit to complete.
I think people have discussed it, I'm not sure if there are any patches floating
around. On the surface, it seems easy to just push the commit_work into the crtc
commit and have one work item per crtc. However I think the problem is that there
could be resources switching between crtcs for a given commit, or from one commit
to the next, and synchronizing that becomes a Hard Problem.
Perhaps I'm misunderstanding, but the start/end atomic functions serialize the
incoming commits, right? So the only benefit the kthread provides is to mitigate
any blocking calls made on one crtc from blocking a second crtc in the same
commit?
Sean
> > - /* only return zero if work is
> > - * queued successfully.
> > - */
> > - ret = 0;
> > - } else {
> > - DRM_ERROR(" Error for crtc_id:
> > %d\n",
> > -
> > priv->disp_thread[j].crtc_id);
> > - }
> > - break;
> > - }
> > - }
> > - /*
> > - * TODO: handle cases where there will be more than
> > - * one crtc per commit cycle. Remove this check then.
> > - * Current assumption is there will be only one crtc
> > - * per commit cycle.
> > - */
> > - if (j < priv->num_crtcs)
> > - break;
> > - }
> > -
> > - if (ret) {
> > - /**
> > - * this is not expected to happen, but at this point the
> > state
> > - * has been swapped, but we couldn't dispatch to a crtc
> > thread.
> > - * fallback now to a synchronous complete_commit to try
> > and
> > - * ensure that SW and HW state don't get out of sync.
> > - */
> > - DRM_ERROR("failed to dispatch commit to any CRTC\n");
> > - complete_commit(commit);
> > - } else if (!nonblock) {
> > - kthread_flush_work(&commit->commit_work);
> > - }
> > -
> > - /* free nonblocking commits in this context, after processing */
> > - if (!nonblock)
> > - kfree(commit);
> > + struct drm_atomic_state *state = container_of(work,
> > + struct
> > drm_atomic_state,
> > + commit_work);
> > + commit_tail(state);
> > }
> >
> > /**
> > @@ -247,17 +122,12 @@ int msm_atomic_commit(struct drm_device *dev,
> > struct drm_atomic_state *state, bool nonblock)
> > {
> > struct msm_drm_private *priv = dev->dev_private;
> > - struct msm_commit *c;
> > struct drm_crtc *crtc;
> > struct drm_crtc_state *crtc_state;
> > struct drm_plane *plane;
> > struct drm_plane_state *old_plane_state, *new_plane_state;
> > int i, ret;
> >
> > - ret = drm_atomic_helper_prepare_planes(dev, state);
> > - if (ret)
> > - return ret;
> > -
> > /*
> > * Note that plane->atomic_async_check() should fail if we need
> > * to re-assign hwpipe or anything that touches global atomic
> > @@ -265,32 +135,30 @@ int msm_atomic_commit(struct drm_device *dev,
> > * cases.
> > */
> > if (state->async_update) {
> > + ret = drm_atomic_helper_prepare_planes(dev, state);
> > + if (ret)
> > + return ret;
> > +
> > drm_atomic_helper_async_commit(dev, state);
> > drm_atomic_helper_cleanup_planes(dev, state);
> > return 0;
> > }
> >
> > - c = commit_init(state, nonblock);
> > - if (!c) {
> > - ret = -ENOMEM;
> > - goto error;
> > - }
> > + ret = drm_atomic_helper_setup_commit(state, nonblock);
> > + if (ret)
> > + return ret;
> >
> > - /*
> > - * Figure out what crtcs we have:
> > - */
> > - for_each_new_crtc_in_state(state, crtc, crtc_state, i)
> > - c->crtc_mask |= drm_crtc_mask(crtc);
> > + INIT_WORK(&state->commit_work, commit_work);
> >
> > - /*
> > - * Wait for pending updates on any of the same crtc's and then
> > - * mark our set of crtc's as busy:
> > - */
> > - ret = start_atomic(dev->dev_private, c->crtc_mask);
> > + ret = drm_atomic_helper_prepare_planes(dev, state);
> > if (ret)
> > - goto err_free;
> > + return ret;
> >
> > - BUG_ON(drm_atomic_helper_swap_state(state, false) < 0);
> > + if (!nonblock) {
> > + ret = drm_atomic_helper_wait_for_fences(dev, state, true);
> > + if (ret)
> > + goto error;
> > + }
> >
> > /*
> > * This is the point of no return - everything below never fails
> > except
> > @@ -299,6 +167,8 @@ int msm_atomic_commit(struct drm_device *dev,
> > *
> > * swap driver private state while still holding state_lock
> > */
> > + BUG_ON(drm_atomic_helper_swap_state(state, false) < 0);
> > +
> > if (to_kms_state(state)->state)
> > priv->kms->funcs->swap_state(priv->kms, state);
> >
> > @@ -329,12 +199,13 @@ int msm_atomic_commit(struct drm_device *dev,
> > */
> >
> > drm_atomic_state_get(state);
> > - msm_atomic_commit_dispatch(dev, state, c);
> > + if (nonblock)
> > + queue_work(system_unbound_wq, &state->commit_work);
> > + else
> > + commit_tail(state);
> >
> > return 0;
> >
> > -err_free:
> > - kfree(c);
> > error:
> > drm_atomic_helper_cleanup_planes(dev, state);
> > return ret;
> > diff --git a/drivers/gpu/drm/msm/msm_drv.c
> > b/drivers/gpu/drm/msm/msm_drv.c
> > index eda4a2340f93..b354424cccb5 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.c
> > +++ b/drivers/gpu/drm/msm/msm_drv.c
> > @@ -549,7 +549,6 @@ static int msm_drm_init(struct device *dev, struct
> > drm_driver *drv)
> > goto mdss_init_fail;
> >
> > priv->wq = alloc_ordered_workqueue("msm_drm", 0);
> > - init_waitqueue_head(&priv->pending_crtcs_event);
> >
> > INIT_LIST_HEAD(&priv->client_event_list);
> > INIT_LIST_HEAD(&priv->inactive_list);
> > diff --git a/drivers/gpu/drm/msm/msm_drv.h
> > b/drivers/gpu/drm/msm/msm_drv.h
> > index cf96a85f4b55..292496b682e8 100644
> > --- a/drivers/gpu/drm/msm/msm_drv.h
> > +++ b/drivers/gpu/drm/msm/msm_drv.h
> > @@ -536,10 +536,6 @@ struct msm_drm_private {
> >
> > struct workqueue_struct *wq;
> >
> > - /* crtcs pending async atomic updates: */
> > - uint32_t pending_crtcs;
> > - wait_queue_head_t pending_crtcs_event;
> > -
> > unsigned int num_planes;
> > struct drm_plane *planes[MAX_PLANES];
--
Sean Paul, Software Engineer, Google / Chromium OS
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