[PATCH 08/10] drm/msm: async commit support

Rob Clark
2019-08-29T17:07:25Z

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>
---
drivers/gpu/drm/msm/msm_atomic.c | 156 ++++++++++++++++++++++++++++++-
drivers/gpu/drm/msm/msm_drv.c | 1 +
drivers/gpu/drm/msm/msm_drv.h | 4 +
drivers/gpu/drm/msm/msm_kms.h | 50 ++++++++++
4 files changed, 210 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
index 614fb9c5bb58..8f8f74337cb4 100644
--- a/drivers/gpu/drm/msm/msm_atomic.c
+++ b/drivers/gpu/drm/msm/msm_atomic.c
@@ -29,6 +29,95 @@ 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.
@@ -50,9 +139,25 @@ 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 is complete,
+ * prepare the current update:
+ */
kms->funcs->prepare_commit(kms, state);

/*
@@ -62,6 +167,49 @@ 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:
*/
@@ -70,12 +218,18 @@ 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 336a6d0a4cd3..65262a993440 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -532,6 +532,7 @@ 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 79d480a7d97d..7d164d5c18b4 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -222,8 +222,12 @@ 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 811f5e2c2405..5eafc9686d29 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 ->perpare_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.
*/

/**
@@ -45,6 +59,14 @@ struct msm_kms_funcs {
void (*enable_commit)(struct msm_kms *kms);
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);
--
2.21.0