[Intel-gfx] [PATCH 2/6] drm/i915: Extract raw GPU timestamps from OA reports to forward in perf samples

[sourab.gupta at intel.com]

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

The OA reports contain the least significant 32 bits of the gpu timestamp.
This patch enables retrieval of the timestamp field from OA reports, to
forward as 64 bit raw gpu timestamps in the perf samples.

Signed-off-by: Sourab Gupta <sourab.gupta at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  1 +
 drivers/gpu/drm/i915/i915_perf.c | 49 +++++++++++++++++++++++++++++-----------
 drivers/gpu/drm/i915/i915_reg.h  |  4 ++++
 3 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index f730477..40ac362 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2643,6 +2643,7 @@ struct drm_i915_private {
 			u32 ctx_flexeu0_off;
 			u32 n_pending_periodic_samples;
 			u32 pending_periodic_ts;
+			u64 last_gpu_ts;
 
 			/* The RPT_ID/reason field for Gen8+ includes a bit
 			 * to determine if the CTX ID in the report is valid
diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 995f7a1..d3d934e 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -1159,6 +1159,26 @@ static int append_sample(struct i915_perf_stream *stream,
 }
 
 /**
+ * get_gpu_ts_from_oa_report - Retrieve absolute gpu timestamp from OA report
+ *
+ * Note: We are assuming that we're updating last_gpu_ts frequently enough so
+ * that it's never possible to see multiple overflows before we compare
+ * sample_ts to last_gpu_ts. Since this is significantly large duration
+ * (~6min for 80ns ts base), we can safely assume so.
+ */
+static u64 get_gpu_ts_from_oa_report(struct drm_i915_private *dev_priv,
+					const u8 *report)
+{
+	u32 sample_ts = *(u32 *)(report + 4);
+	u32 delta;
+
+	delta = sample_ts - (u32)dev_priv->perf.oa.last_gpu_ts;
+	dev_priv->perf.oa.last_gpu_ts += delta;
+
+	return dev_priv->perf.oa.last_gpu_ts;
+}
+
+/**
  * append_oa_buffer_sample - Copies single periodic OA report into userspace
  * read() buffer.
  * @stream: An i915-perf stream opened for OA metrics
@@ -1189,11 +1209,8 @@ static int append_oa_buffer_sample(struct i915_perf_stream *stream,
 	if (sample_flags & SAMPLE_TAG)
 		data.tag = dev_priv->perf.last_tag;
 
-	/* TODO: Derive timestamp from OA report,
-	 * after scaling with the ts base
-	 */
 	if (sample_flags & SAMPLE_TS)
-		data.ts = 0;
+		data.ts = get_gpu_ts_from_oa_report(dev_priv, report);
 
 	if (sample_flags & SAMPLE_OA_REPORT)
 		data.report = report;
@@ -1752,6 +1769,7 @@ static int append_one_cs_sample(struct i915_perf_stream *stream,
 	struct sample_data data = { 0 };
 	enum intel_engine_id id = stream->engine;
 	u32 sample_flags = stream->sample_flags;
+	u64 gpu_ts = 0;
 	int ret = 0;
 
 	if (sample_flags & SAMPLE_OA_REPORT) {
@@ -1768,6 +1786,9 @@ static int append_one_cs_sample(struct i915_perf_stream *stream,
 						sample_ts, U32_MAX);
 		if (ret)
 			return ret;
+
+		if (sample_flags & SAMPLE_TS)
+			gpu_ts = get_gpu_ts_from_oa_report(dev_priv, report);
 	}
 
 	if (sample_flags & SAMPLE_OA_SOURCE_INFO)
@@ -1789,18 +1810,14 @@ static int append_one_cs_sample(struct i915_perf_stream *stream,
 	}
 
 	if (sample_flags & SAMPLE_TS) {
-		/* For RCS, if OA samples are also being collected, derive the
-		 * timestamp from OA report, after scaling with the TS base.
+		/* If OA sampling is enabled, derive the ts from OA report.
 		 * Else, forward the timestamp collected via command stream.
 		 */
-
-		/* TODO: derive the timestamp from OA report */
-		if (sample_flags & SAMPLE_OA_REPORT)
-			data.ts = 0;
-		else
-			data.ts = *(u64 *)
+		if (!(sample_flags & SAMPLE_OA_REPORT))
+			gpu_ts = *(u64 *)
 				(dev_priv->perf.command_stream_buf[id].vaddr +
 					node->ts_offset);
+		data.ts = gpu_ts;
 	}
 
 	return append_sample(stream, buf, count, offset, &data);
@@ -2815,9 +2832,15 @@ static void i915_engine_stream_enable(struct i915_perf_stream *stream)
 {
 	struct drm_i915_private *dev_priv = stream->dev_priv;
 
-	if (stream->sample_flags & SAMPLE_OA_REPORT)
+	if (stream->sample_flags & SAMPLE_OA_REPORT) {
 		dev_priv->perf.oa.ops.oa_enable(dev_priv);
 
+		if (stream->sample_flags & SAMPLE_TS)
+			dev_priv->perf.oa.last_gpu_ts =
+				I915_READ64_2x32(GT_TIMESTAMP_COUNT,
+					GT_TIMESTAMP_COUNT_UDW);
+	}
+
 	if (stream->cs_mode || dev_priv->perf.oa.periodic)
 		hrtimer_start(&dev_priv->perf.poll_check_timer,
 			      ns_to_ktime(POLL_PERIOD),
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index ea312fc..fe8bab4 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -600,6 +600,10 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
 #define PS_DEPTH_COUNT                  _MMIO(0x2350)
 #define PS_DEPTH_COUNT_UDW		_MMIO(0x2350 + 4)
 
+/* Timestamp count register */
+#define GT_TIMESTAMP_COUNT		_MMIO(0x2358)
+#define GT_TIMESTAMP_COUNT_UDW		_MMIO(0x2358 + 4)
+
 /* There are the 4 64-bit counter registers, one for each stream output */
 #define GEN7_SO_NUM_PRIMS_WRITTEN(n)		_MMIO(0x5200 + (n) * 8)
 #define GEN7_SO_NUM_PRIMS_WRITTEN_UDW(n)	_MMIO(0x5200 + (n) * 8 + 4)
-- 
1.9.1