[PATCH 1/2] drm/atomic: Add struct drm_crtc_commit to track async updates

[Daniel Vetter <daniel.vetter@ffwll.ch>]

Split out from my big nonblocking atomic commit helper code as prep
work. While add it, also add some neat asciiart to document how it's
supposed to be used.

Tested-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Tomeu Vizoso <tomeu.vizoso@gmail.com>
Cc: Daniel Stone <daniels@collabora.com>
Tested-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/drm_atomic.c |  22 +++++++
 drivers/gpu/drm/drm_crtc.c   |   3 +
 drivers/gpu/drm/drm_fops.c   |   6 ++
 include/drm/drmP.h           |   1 +
 include/drm/drm_atomic.h     |   6 ++
 include/drm/drm_crtc.h       | 146 +++++++++++++++++++++++++++++++++++++++++--
 6 files changed, 178 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 5e4b820a977c..d99ab2f6663f 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -33,6 +33,20 @@
 
 #include "drm_crtc_internal.h"
 
+static void crtc_commit_free(struct kref *kref)
+{
+	struct drm_crtc_commit *commit =
+		container_of(kref, struct drm_crtc_commit, ref);
+
+	kfree(commit);
+}
+
+void drm_crtc_commit_put(struct drm_crtc_commit *commit)
+{
+	kref_put(&commit->ref, crtc_commit_free);
+}
+EXPORT_SYMBOL(drm_crtc_commit_put);
+
 /**
  * drm_atomic_state_default_release -
  * release memory initialized by drm_atomic_state_init
@@ -148,6 +162,14 @@ void drm_atomic_state_default_clear(struct drm_atomic_state *state)
 
 		crtc->funcs->atomic_destroy_state(crtc,
 						  state->crtcs[i].state);
+
+		if (state->crtcs[i].commit) {
+			kfree(state->crtcs[i].commit->event);
+			state->crtcs[i].commit->event = NULL;
+			drm_crtc_commit_put(state->crtcs[i].commit);
+		}
+
+		state->crtcs[i].commit = NULL;
 		state->crtcs[i].ptr = NULL;
 		state->crtcs[i].state = NULL;
 	}
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 1cb3b471aadc..1f14c6565210 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -669,6 +669,9 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
 	crtc->dev = dev;
 	crtc->funcs = funcs;
 
+	INIT_LIST_HEAD(&crtc->commit_list);
+	spin_lock_init(&crtc->commit_lock);
+
 	drm_modeset_lock_init(&crtc->mutex);
 	ret = drm_mode_object_get(dev, &crtc->base, DRM_MODE_OBJECT_CRTC);
 	if (ret)
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 4c4b30f7a9f2..5921b203503a 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -686,6 +686,12 @@ void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e)
 {
 	assert_spin_locked(&dev->event_lock);
 
+	if (e->completion) {
+		/* ->completion might disappear as soon as it signalled. */
+		complete_all(e->completion);
+		e->completion = NULL;
+	}
+
 	if (e->fence) {
 		fence_signal(e->fence);
 		fence_put(e->fence);
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 51f751d1c8a4..781db4f562d4 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -283,6 +283,7 @@ struct drm_ioctl_desc {
 
 /* Event queued up for userspace to read */
 struct drm_pending_event {
+	struct completion *completion;
 	struct drm_event *event;
 	struct fence *fence;
 	struct list_head link;
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 465a1212f4f0..abec2a3f0225 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -30,6 +30,12 @@
 
 #include <drm/drm_crtc.h>
 
+void drm_crtc_commit_put(struct drm_crtc_commit *commit);
+static inline void drm_crtc_commit_get(struct drm_crtc_commit *commit)
+{
+	kref_get(&commit->ref);
+}
+
 struct drm_atomic_state * __must_check
 drm_atomic_state_alloc(struct drm_device *dev);
 void drm_atomic_state_clear(struct drm_atomic_state *state);
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index d5d5e343531e..cf4aad0929d9 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -725,9 +725,6 @@ struct drm_crtc_funcs {
  * @gamma_store: gamma ramp values
  * @helper_private: mid-layer private data
  * @properties: property tracking for this CRTC
- * @state: current atomic state for this CRTC
- * @acquire_ctx: per-CRTC implicit acquire context used by atomic drivers for
- * 	legacy IOCTLs
  *
  * Each CRTC may have one or more connectors associated with it.  This structure
  * allows the CRTC to be controlled.
@@ -780,11 +777,37 @@ struct drm_crtc {
 
 	struct drm_object_properties properties;
 
+	/**
+	 * @state:
+	 *
+	 * Current atomic state for this CRTC.
+	 */
 	struct drm_crtc_state *state;
 
-	/*
-	 * For legacy crtc IOCTLs so that atomic drivers can get at the locking
-	 * acquire context.
+	/**
+	 * @commit_list:
+	 *
+	 * List of &drm_crtc_commit structures tracking pending commits.
+	 * Protected by @commit_lock. This list doesn't hold its own full
+	 * reference, but burrows it from the ongoing commit. Commit entries
+	 * must be removed from this list once the commit is fully completed,
+	 * but before it's correspoding &drm_atomic_state gets destroyed.
+	 */
+	struct list_head commit_list;
+
+	/**
+	 * @commit_lock:
+	 *
+	 * Spinlock to protect @commit_list.
+	 */
+	spinlock_t commit_lock;
+
+	/**
+	 * @acquire_ctx:
+	 *
+	 * Per-CRTC implicit acquire context used by atomic drivers for legacy
+	 * IOCTLs, so that atomic drivers can get at the locking acquire
+	 * context.
 	 */
 	struct drm_modeset_acquire_ctx *acquire_ctx;
 };
@@ -1694,6 +1717,108 @@ struct drm_bridge {
 	void *driver_private;
 };
 
+/**
+ * struct drm_crtc_commit - track modeset commits on a CRTC
+ *
+ * This structure is used to track pending modeset changes and atomic commit on
+ * a per-CRTC basis. Since updating the list should never block this structure
+ * is reference counted to allow waiters to safely wait on an event to complete,
+ * without holding any locks.
+ *
+ * It has 3 different events in total to allow a fine-grained synchronoization
+ * between outstanding updates::
+ *
+ *	atomic commit thread			hardware
+ *
+ * 	write new state into hardware	---->	...
+ * 	signal hw_done
+ * 						switch to new state on next
+ * 	...					v/hblank
+ *
+ *	wait for buffers to show up		...
+ *
+ *	...					send completion irq
+ *						irq handler signals flip_done
+ *	cleanup old buffers
+ *
+ * 	signal cleanup_done
+ *
+ * 	wait for flip_done		<----
+ * 	clean up atomic state
+ * 
+ * The important bit to know is that cleanup_done is the terminal event, but the
+ * ordering between flip_done and hw_done is entirely up to the specific driver
+ * and modeset state change.
+ */
+struct drm_crtc_commit {
+	/**
+	 * @crtc:
+	 *
+	 * DRM CRTC for this commit.
+	 */
+	struct drm_crtc *crtc;
+
+	/**
+	 * @ref:
+	 *
+	 * Reference count for this structure. Needed to allow blocking on
+	 * completions without the risk of the completion disappearing
+	 * meanwhile.
+	 */
+	struct kref ref;
+
+	/**
+	 * @flip_done:
+	 *
+	 * Will be signaled when the hardware has flipped to the new set of
+	 * buffers. Signals at the same time as when the drm event for this
+	 * commit is sent to userspace, or when an out-fence is singalled. Note
+	 * that for most hardware, in most cases this happens after @hw_done is
+	 * signalled.
+	 */
+	struct completion flip_done;
+
+	/**
+	 * @hw_done:
+	 *
+	 * Will be signalled when all hw register changes for this commit have
+	 * been written out. Especially when disabling a pipe this can be much
+	 * later than than @flip_done, since that can signal already when the
+	 * screen goes black, whereas to fully shut down a pipe more register
+	 * I/O is required.
+	 *
+	 * Note that this does not need to include separately reference-counted
+	 * resources like backing storage buffer pinning, or runtime pm
+	 * management.
+	 */
+	struct completion hw_done;
+
+	/**
+	 * cleanup_done:
+	 *
+	 * Will be signalled after old buffers have been cleaned up again by
+	 * calling drm_atomic_helper_cleanup_planes(). Since this can only
+	 * happen after a vblank wait completed it might be a bit later. This
+	 * completion is useful to throttle updates and avoid hardware updates
+	 * getting ahead of the buffer cleanup too much.
+	 */
+	struct completion cleanup_done;
+
+	/**
+	 * @commit_entry:
+	 *
+	 * Entry on the per-CRTC commit_list. Protected by crtc->commit_lock.
+	 */
+	struct list_head commit_entry;
+
+	/**
+	 * @event:
+	 *
+	 * &drm_pending_vblank_event pointer to clean up private events.
+	 */
+	struct drm_pending_vblank_event *event;
+};
+
 struct __drm_planes_state {
 	struct drm_plane *ptr;
 	struct drm_plane_state *state;
@@ -1702,6 +1827,7 @@ struct __drm_planes_state {
 struct __drm_crtcs_state {
 	struct drm_crtc *ptr;
 	struct drm_crtc_state *state;
+	struct drm_crtc_commit *commit;
 };
 
 struct __drm_connnectors_state {
@@ -1733,6 +1859,14 @@ struct drm_atomic_state {
 	struct __drm_connnectors_state *connectors;
 
 	struct drm_modeset_acquire_ctx *acquire_ctx;
+
+	/**
+	 * @commit_work:
+	 *
+	 * Work item which can be used by the driver or helpers to execute the
+	 * commit without blocking.
+	 */
+	struct work_struct commit_work;
 };
 
 
-- 
2.8.1

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