drm/msm: async commit support

Now that flush/wait/complete is decoupled from the "synchronous" part of
atomic commit_tail(), add support to defer flush to a timer that expires
shortly before vblank for async commits.  In this way, multiple atomic
commits (for example, cursor updates) can be coalesced into a single
flush at the end of the frame.

v2: don't hold lock over ->wait_flush(), to avoid locking interaction
    that was causing fps drop when combining page flips or non-async
    atomic commits and lots of legacy cursor updates

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Sean Paul <sean@poorly.run>

4 files changed, 210 insertions, 1 deletions

diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
index 517d3a747778..55c8d72f8401 100644
--- a/drivers/gpu/drm/msm/msm_atomic.c
+++ b/drivers/gpu/drm/msm/msm_atomic.c
@@ -26,6 +26,95 @@ int msm_atomic_prepare_fb(struct drm_plane *plane,
         return msm_framebuffer_prepare(new_state->fb, kms->aspace);
 }
 
+static void msm_atomic_async_commit(struct msm_kms *kms, int crtc_idx)
+{
+        unsigned crtc_mask = BIT(crtc_idx);
+
+        mutex_lock(&kms->commit_lock);
+
+        if (!(kms->pending_crtc_mask & crtc_mask)) {
+                mutex_unlock(&kms->commit_lock);
+                return;
+        }
+
+        kms->pending_crtc_mask &= ~crtc_mask;
+
+        kms->funcs->enable_commit(kms);
+
+        /*
+         * Flush hardware updates:
+         */
+        DRM_DEBUG_ATOMIC("triggering async commit\n");
+        kms->funcs->flush_commit(kms, crtc_mask);
+        mutex_unlock(&kms->commit_lock);
+
+        /*
+         * Wait for flush to complete:
+         */
+        kms->funcs->wait_flush(kms, crtc_mask);
+
+        mutex_lock(&kms->commit_lock);
+        kms->funcs->complete_commit(kms, crtc_mask);
+        mutex_unlock(&kms->commit_lock);
+        kms->funcs->disable_commit(kms);
+}
+
+static enum hrtimer_restart msm_atomic_pending_timer(struct hrtimer *t)
+{
+        struct msm_pending_timer *timer = container_of(t,
+                        struct msm_pending_timer, timer);
+        struct msm_drm_private *priv = timer->kms->dev->dev_private;
+
+        queue_work(priv->wq, &timer->work);
+
+        return HRTIMER_NORESTART;
+}
+
+static void msm_atomic_pending_work(struct work_struct *work)
+{
+        struct msm_pending_timer *timer = container_of(work,
+                        struct msm_pending_timer, work);
+
+        msm_atomic_async_commit(timer->kms, timer->crtc_idx);
+}
+
+void msm_atomic_init_pending_timer(struct msm_pending_timer *timer,
+                struct msm_kms *kms, int crtc_idx)
+{
+        timer->kms = kms;
+        timer->crtc_idx = crtc_idx;
+        hrtimer_init(&timer->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+        timer->timer.function = msm_atomic_pending_timer;
+        INIT_WORK(&timer->work, msm_atomic_pending_work);
+}
+
+static bool can_do_async(struct drm_atomic_state *state,
+                struct drm_crtc **async_crtc)
+{
+        struct drm_connector_state *connector_state;
+        struct drm_connector *connector;
+        struct drm_crtc_state *crtc_state;
+        struct drm_crtc *crtc;
+        int i, num_crtcs = 0;
+
+        if (!(state->legacy_cursor_update || state->async_update))
+                return false;
+
+        /* any connector change, means slow path: */
+        for_each_new_connector_in_state(state, connector, connector_state, i)
+                return false;
+
+        for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
+                if (drm_atomic_crtc_needs_modeset(crtc_state))
+                        return false;
+                if (++num_crtcs > 1)
+                        return false;
+                *async_crtc = crtc;
+        }
+
+        return true;
+}
+
 /* Get bitmask of crtcs that will need to be flushed.  The bitmask
  * can be used with for_each_crtc_mask() iterator, to iterate
  * effected crtcs without needing to preserve the atomic state.
@@ -47,9 +136,25 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
         struct drm_device *dev = state->dev;
         struct msm_drm_private *priv = dev->dev_private;
         struct msm_kms *kms = priv->kms;
+        struct drm_crtc *async_crtc = NULL;
         unsigned crtc_mask = get_crtc_mask(state);
+        bool async = kms->funcs->vsync_time &&
+                        can_do_async(state, &async_crtc);
 
         kms->funcs->enable_commit(kms);
+
+        /*
+         * Ensure any previous (potentially async) commit has
+         * completed:
+         */
+        kms->funcs->wait_flush(kms, crtc_mask);
+
+        mutex_lock(&kms->commit_lock);
+
+        /*
+         * Now that there is no in-progress flush, prepare the
+         * current update:
+         */
         kms->funcs->prepare_commit(kms, state);
 
         /*
@@ -59,6 +164,49 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
         drm_atomic_helper_commit_planes(dev, state, 0);
         drm_atomic_helper_commit_modeset_enables(dev, state);
 
+        if (async) {
+                struct msm_pending_timer *timer =
+                        &kms->pending_timers[drm_crtc_index(async_crtc)];
+
+                /* async updates are limited to single-crtc updates: */
+                WARN_ON(crtc_mask != drm_crtc_mask(async_crtc));
+
+                /*
+                 * Start timer if we don't already have an update pending
+                 * on this crtc:
+                 */
+                if (!(kms->pending_crtc_mask & crtc_mask)) {
+                        ktime_t vsync_time, wakeup_time;
+
+                        kms->pending_crtc_mask |= crtc_mask;
+
+                        vsync_time = kms->funcs->vsync_time(kms, async_crtc);
+                        wakeup_time = ktime_sub(vsync_time, ms_to_ktime(1));
+
+                        hrtimer_start(&timer->timer, wakeup_time,
+                                        HRTIMER_MODE_ABS);
+                }
+
+                kms->funcs->disable_commit(kms);
+                mutex_unlock(&kms->commit_lock);
+
+                /*
+                 * At this point, from drm core's perspective, we
+                 * are done with the atomic update, so we can just
+                 * go ahead and signal that it is done:
+                 */
+                drm_atomic_helper_commit_hw_done(state);
+                drm_atomic_helper_cleanup_planes(dev, state);
+
+                return;
+        }
+
+        /*
+         * If there is any async flush pending on updated crtcs, fold
+         * them into the current flush.
+         */
+        kms->pending_crtc_mask &= ~crtc_mask;
+
         /*
          * Flush hardware updates:
          */
@@ -67,12 +215,18 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
                 kms->funcs->commit(kms, state);
         }
         kms->funcs->flush_commit(kms, crtc_mask);
+        mutex_unlock(&kms->commit_lock);
 
+        /*
+         * Wait for flush to complete:
+         */
         kms->funcs->wait_flush(kms, crtc_mask);
+
+        mutex_lock(&kms->commit_lock);
         kms->funcs->complete_commit(kms, crtc_mask);
+        mutex_unlock(&kms->commit_lock);
         kms->funcs->disable_commit(kms);
 
         drm_atomic_helper_commit_hw_done(state);
-
         drm_atomic_helper_cleanup_planes(dev, state);
 }
diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index 996a508f762c..c84f0a8b3f2c 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -473,6 +473,7 @@ static int msm_drm_init(struct device *dev, struct drm_driver *drv)
         ddev->mode_config.normalize_zpos = true;
 
         if (kms) {
+                kms->dev = ddev;
                 ret = kms->funcs->hw_init(kms);
                 if (ret) {
                         DRM_DEV_ERROR(dev, "kms hw init failed: %d\n", ret);
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 1fa0974eb69f..71547e756e29 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -221,8 +221,12 @@ struct msm_format {
         uint32_t pixel_format;
 };
 
+struct msm_pending_timer;
+
 int msm_atomic_prepare_fb(struct drm_plane *plane,
                           struct drm_plane_state *new_state);
+void msm_atomic_init_pending_timer(struct msm_pending_timer *timer,
+                struct msm_kms *kms, int crtc_idx);
 void msm_atomic_commit_tail(struct drm_atomic_state *state);
 struct drm_atomic_state *msm_atomic_state_alloc(struct drm_device *dev);
 void msm_atomic_state_clear(struct drm_atomic_state *state);
diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h
index 85264a2f1f6d..ed8df60a32ad 100644
--- a/drivers/gpu/drm/msm/msm_kms.h
+++ b/drivers/gpu/drm/msm/msm_kms.h
@@ -33,6 +33,20 @@ struct msm_kms_funcs {
 
         /*
          * Atomic commit handling:
+         *
+         * Note that in the case of async commits, the funcs which take
+         * a crtc_mask (ie. ->flush_commit(), and ->complete_commit())
+         * might not be evenly balanced with ->prepare_commit(), however
+         * each crtc that effected by a ->prepare_commit() (potentially
+         * multiple times) will eventually (at end of vsync period) be
+         * flushed and completed.
+         *
+         * This has some implications about tracking of cleanup state,
+         * for example SMP blocks to release after commit completes.  Ie.
+         * cleanup state should be also duplicated in the various
+         * duplicate_state() methods, as the current cleanup state at
+         * ->complete_commit() time may have accumulated cleanup work
+         * from multiple commits.
          */
 
         /**
@@ -46,6 +60,14 @@ struct msm_kms_funcs {
         void (*disable_commit)(struct msm_kms *kms);
 
         /**
+         * If the kms backend supports async commit, it should implement
+         * this method to return the time of the next vsync.  This is
+         * used to determine a time slightly before vsync, for the async
+         * commit timer to run and complete an async commit.
+         */
+        ktime_t (*vsync_time)(struct msm_kms *kms, struct drm_crtc *crtc);
+
+        /**
          * Prepare for atomic commit.  This is called after any previous
          * (async or otherwise) commit has completed.
          */
@@ -109,20 +131,48 @@ struct msm_kms_funcs {
 #endif
 };
 
+struct msm_kms;
+
+/*
+ * A per-crtc timer for pending async atomic flushes.  Scheduled to expire
+ * shortly before vblank to flush pending async updates.
+ */
+struct msm_pending_timer {
+        struct hrtimer timer;
+        struct work_struct work;
+        struct msm_kms *kms;
+        unsigned crtc_idx;
+};
+
 struct msm_kms {
         const struct msm_kms_funcs *funcs;
+        struct drm_device *dev;
 
         /* irq number to be passed on to drm_irq_install */
         int irq;
 
         /* mapper-id used to request GEM buffer mapped for scanout: */
         struct msm_gem_address_space *aspace;
+
+        /*
+         * For async commit, where ->flush_commit() and later happens
+         * from the crtc's pending_timer close to end of the frame:
+         */
+        struct mutex commit_lock;
+        unsigned pending_crtc_mask;
+        struct msm_pending_timer pending_timers[MAX_CRTCS];
 };
 
 static inline void msm_kms_init(struct msm_kms *kms,
                 const struct msm_kms_funcs *funcs)
 {
+        unsigned i;
+
+        mutex_init(&kms->commit_lock);
         kms->funcs = funcs;
+
+        for (i = 0; i < ARRAY_SIZE(kms->pending_timers); i++)
+                msm_atomic_init_pending_timer(&kms->pending_timers[i], kms, i);
 }
 
 struct msm_kms *mdp4_kms_init(struct drm_device *dev);