[RFC 4/7] drm/i915: Add mechanism for forwarding the data samples to userspace through Gen PMU perf interface

[sourab.gupta@intel.com]

From: Sourab Gupta <sourab.gupta@intel.com>

This patch adds the mechanism for forwarding the data snapshots
through the Gen PMU perf event interface.
In this particular case, the data type of timestamp data node introduced
earlier is being forwarded through the interface.

The samples will be forwarded in a workqueue, which is scheduled when hrtimer
triggers. In the workqueue, each node of data collected will be forwarded as a
separate perf sample.

Signed-off-by: Sourab Gupta <sourab.gupta@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h     |   1 +
 drivers/gpu/drm/i915/i915_oa_perf.c | 125 +++++++++++++++++++++++++++++++++++-
 2 files changed, 124 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index b6a897a..25c0938 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2021,6 +2021,7 @@ struct drm_i915_private {
 			u32 head;
 			u32 tail;
 		} buffer;
+		struct work_struct work_timer;
 	} gen_pmu;
 
 	struct list_head profile_cmd;
diff --git a/drivers/gpu/drm/i915/i915_oa_perf.c b/drivers/gpu/drm/i915/i915_oa_perf.c
index e2042b6..e3e867f 100644
--- a/drivers/gpu/drm/i915/i915_oa_perf.c
+++ b/drivers/gpu/drm/i915/i915_oa_perf.c
@@ -224,11 +224,121 @@ void forward_oa_async_snapshots_work(struct work_struct *__work)
 	mutex_unlock(&dev_priv->dev->struct_mutex);
 }
 
+static void init_gen_pmu_buf_queue(struct drm_i915_private *dev_priv)
+{
+	struct drm_i915_ts_queue_header *hdr =
+		(struct drm_i915_ts_queue_header *)
+		dev_priv->gen_pmu.buffer.addr;
+	void *data_ptr;
+
+	hdr->size_in_bytes = dev_priv->gen_pmu.buffer.obj->base.size;
+	/* 8 byte alignment for node address */
+	data_ptr = PTR_ALIGN((void *)(hdr + 1), 8);
+	hdr->data_offset = (__u64)(data_ptr - (void *)hdr);
+
+	hdr->node_count = 0;
+	hdr->wrap_count = 0;
+}
+
+static void forward_one_gen_pmu_sample(struct drm_i915_private *dev_priv,
+				struct drm_i915_ts_node *node)
+{
+	struct perf_sample_data data;
+	struct perf_event *event = dev_priv->gen_pmu.exclusive_event;
+	int snapshot_size = sizeof(struct drm_i915_ts_usernode);
+	struct perf_raw_record raw;
+
+	perf_sample_data_init(&data, 0, event->hw.last_period);
+
+	/* Note: the combined u32 raw->size member + raw data itself must be 8
+	 * byte aligned.*/
+	raw.size = snapshot_size + 4;
+	raw.data = node;
+
+	data.raw = &raw;
+
+	perf_event_overflow(event, &data, &dev_priv->gen_pmu.dummy_regs);
+}
+
+void i915_gen_pmu_wait_gpu(struct drm_i915_private *dev_priv)
+{
+	struct drm_i915_ts_queue_header *hdr =
+		(struct drm_i915_ts_queue_header *)
+		dev_priv->gen_pmu.buffer.addr;
+	struct drm_i915_ts_node *first_node, *node;
+	int head, tail, num_nodes, ret;
+	struct drm_i915_gem_request *req;
+
+	first_node = (struct drm_i915_ts_node *)
+			((char *)hdr + hdr->data_offset);
+	num_nodes = (hdr->size_in_bytes - hdr->data_offset) /
+			sizeof(*node);
+
+	tail = hdr->node_count;
+	head = dev_priv->gen_pmu.buffer.head;
+
+	/* wait for all requests to complete*/
+	while ((head % num_nodes) != (tail % num_nodes)) {
+		node = &first_node[head % num_nodes];
+		req = node->node_info.req;
+		if (req) {
+			if (!i915_gem_request_completed(req, true)) {
+				ret = i915_wait_request(req);
+				if (ret)
+					DRM_DEBUG_DRIVER(
+					"gen pmu: failed to wait\n");
+			}
+			i915_gem_request_assign(&node->node_info.req, NULL);
+		}
+		head++;
+	}
+}
+
+void forward_gen_pmu_snapshots_work(struct work_struct *__work)
+{
+	struct drm_i915_private *dev_priv =
+		container_of(__work, typeof(*dev_priv),
+			     gen_pmu.work_timer);
+	struct drm_i915_ts_queue_header *hdr =
+		(struct drm_i915_ts_queue_header *)
+		dev_priv->gen_pmu.buffer.addr;
+	struct drm_i915_ts_node *first_node, *node;
+	int head, tail, num_nodes, ret;
+	struct drm_i915_gem_request *req;
+
+	first_node = (struct drm_i915_ts_node *)
+			((char *)hdr + hdr->data_offset);
+	num_nodes = (hdr->size_in_bytes - hdr->data_offset) /
+			sizeof(*node);
+
+	ret = i915_mutex_lock_interruptible(dev_priv->dev);
+	if (ret)
+		return;
+
+	tail = hdr->node_count;
+	head = dev_priv->gen_pmu.buffer.head;
+
+	while ((head % num_nodes) != (tail % num_nodes)) {
+		node = &first_node[head % num_nodes];
+		req = node->node_info.req;
+		if (req && i915_gem_request_completed(req, true)) {
+			forward_one_gen_pmu_sample(dev_priv, node);
+			i915_gem_request_assign(&node->node_info.req, NULL);
+			head++;
+		} else
+			break;
+	}
+
+	dev_priv->gen_pmu.buffer.tail = tail;
+	dev_priv->gen_pmu.buffer.head = head;
+
+	mutex_unlock(&dev_priv->dev->struct_mutex);
+}
+
 static void gen_pmu_flush_snapshots(struct drm_i915_private *dev_priv)
 {
 	WARN_ON(!dev_priv->gen_pmu.buffer.addr);
-
-	/* TODO: routine for forwarding snapshots to userspace */
+	schedule_work(&dev_priv->gen_pmu.work_timer);
 }
 
 static void forward_one_oa_snapshot_to_event(struct drm_i915_private *dev_priv,
@@ -652,6 +762,7 @@ static int init_gen_pmu_buffer(struct perf_event *event)
 	dev_priv->gen_pmu.buffer.obj = bo;
 
 	dev_priv->gen_pmu.buffer.addr = vmap_oa_buffer(bo);
+	init_gen_pmu_buf_queue(dev_priv);
 
 	DRM_DEBUG_DRIVER("Gen PMU Buffer initialized, vaddr = %p",
 			 dev_priv->gen_pmu.buffer.addr);
@@ -1327,6 +1438,13 @@ static void i915_gen_event_flush(struct perf_event *event)
 {
 	struct drm_i915_private *i915 =
 		container_of(event->pmu, typeof(*i915), gen_pmu.pmu);
+	int ret;
+
+	ret = i915_mutex_lock_interruptible(i915->dev);
+	if (ret)
+		return;
+	i915_gen_pmu_wait_gpu(i915);
+	mutex_unlock(&i915->dev->struct_mutex);
 
 	gen_pmu_flush_snapshots(i915);
 }
@@ -1476,6 +1594,7 @@ void i915_gen_pmu_register(struct drm_device *dev)
 	hrtimer_init(&i915->gen_pmu.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	i915->gen_pmu.timer.function = hrtimer_sample_gen;
 
+	INIT_WORK(&i915->gen_pmu.work_timer, forward_gen_pmu_snapshots_work);
 	spin_lock_init(&i915->gen_pmu.lock);
 
 	i915->gen_pmu.pmu.capabilities  = PERF_PMU_CAP_IS_DEVICE;
@@ -1505,6 +1624,8 @@ void i915_gen_pmu_unregister(struct drm_device *dev)
 	if (i915->gen_pmu.pmu.event_init == NULL)
 		return;
 
+	cancel_work_sync(&i915->gen_pmu.work_timer);
+
 	perf_pmu_unregister(&i915->gen_pmu.pmu);
 	i915->gen_pmu.pmu.event_init = NULL;
 }
-- 
1.8.5.1

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