[PATCH v2 1/6] drm/xe/lrc: Add helper to capture context timestamp

[Lucas De Marchi <lucas.demarchi@xxxxxxxxx>]

From: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>

Add a helper to capture CTX_TIMESTAMP from the context image so it can
be used to calculate the runtime.

v2: Add kernel-doc to clarify expectation from caller

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
---
 drivers/gpu/drm/xe/regs/xe_lrc_layout.h |  1 +
 drivers/gpu/drm/xe/xe_lrc.c             | 11 +++++++++++
 drivers/gpu/drm/xe/xe_lrc.h             | 14 ++++++++++++++
 drivers/gpu/drm/xe/xe_lrc_types.h       |  3 +++
 4 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/xe/regs/xe_lrc_layout.h b/drivers/gpu/drm/xe/regs/xe_lrc_layout.h
index 1825d8f79db6..8780e6c6b649 100644
--- a/drivers/gpu/drm/xe/regs/xe_lrc_layout.h
+++ b/drivers/gpu/drm/xe/regs/xe_lrc_layout.h
@@ -11,6 +11,7 @@
 #define CTX_RING_TAIL			(0x06 + 1)
 #define CTX_RING_START			(0x08 + 1)
 #define CTX_RING_CTL			(0x0a + 1)
+#define CTX_TIMESTAMP			(0x22 + 1)
 #define CTX_PDP0_UDW			(0x30 + 1)
 #define CTX_PDP0_LDW			(0x32 + 1)
 
diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
index 615bbc372ac6..4bfd8f9c3b46 100644
--- a/drivers/gpu/drm/xe/xe_lrc.c
+++ b/drivers/gpu/drm/xe/xe_lrc.c
@@ -751,6 +751,7 @@ int xe_lrc_init(struct xe_lrc *lrc, struct xe_hw_engine *hwe,
 	lrc->tile = gt_to_tile(hwe->gt);
 	lrc->ring.size = ring_size;
 	lrc->ring.tail = 0;
+	lrc->ctx_timestamp = 0;
 
 	xe_hw_fence_ctx_init(&lrc->fence_ctx, hwe->gt,
 			     hwe->fence_irq, hwe->name);
@@ -786,6 +787,7 @@ int xe_lrc_init(struct xe_lrc *lrc, struct xe_hw_engine *hwe,
 			xe_drm_client_add_bo(vm->xef->client, lrc->bo);
 	}
 
+	xe_lrc_write_ctx_reg(lrc, CTX_TIMESTAMP, 0);
 	xe_lrc_write_ctx_reg(lrc, CTX_RING_START, __xe_lrc_ring_ggtt_addr(lrc));
 	xe_lrc_write_ctx_reg(lrc, CTX_RING_HEAD, 0);
 	xe_lrc_write_ctx_reg(lrc, CTX_RING_TAIL, lrc->ring.tail);
@@ -1444,3 +1446,12 @@ void xe_lrc_snapshot_free(struct xe_lrc_snapshot *snapshot)
 		xe_bo_put(snapshot->lrc_bo);
 	kfree(snapshot);
 }
+
+u32 xe_lrc_update_timestamp(struct xe_lrc *lrc, u32 *old_ts)
+{
+	*old_ts = lrc->ctx_timestamp;
+
+	lrc->ctx_timestamp = xe_lrc_read_ctx_reg(lrc, CTX_TIMESTAMP);
+
+	return lrc->ctx_timestamp;
+}
diff --git a/drivers/gpu/drm/xe/xe_lrc.h b/drivers/gpu/drm/xe/xe_lrc.h
index d32fa31faa2c..dcbc6edd80da 100644
--- a/drivers/gpu/drm/xe/xe_lrc.h
+++ b/drivers/gpu/drm/xe/xe_lrc.h
@@ -60,4 +60,18 @@ void xe_lrc_snapshot_capture_delayed(struct xe_lrc_snapshot *snapshot);
 void xe_lrc_snapshot_print(struct xe_lrc_snapshot *snapshot, struct drm_printer *p);
 void xe_lrc_snapshot_free(struct xe_lrc_snapshot *snapshot);
 
+/**
+ * xe_lrc_update_timestamp - readout LRC timestamp and update cached value
+ * @lrc: logical ring context for this exec queue
+ * @old_ts: pointer where to save the previous timestamp
+ *
+ * Read the current timestamp for this LRC and update the cached value. The
+ * previous cached value is also returned in @old_ts so the caller can calculate
+ * the delta between 2 updates. Note that this is not intended to be called from
+ * any place, but just by the paths updating the drm client utilization.
+ *
+ * Returns the current LRC timestamp
+ */
+u32 xe_lrc_update_timestamp(struct xe_lrc *lrc, u32 *old_ts);
+
 #endif
diff --git a/drivers/gpu/drm/xe/xe_lrc_types.h b/drivers/gpu/drm/xe/xe_lrc_types.h
index b716df0dfb4e..5765d771b901 100644
--- a/drivers/gpu/drm/xe/xe_lrc_types.h
+++ b/drivers/gpu/drm/xe/xe_lrc_types.h
@@ -41,6 +41,9 @@ struct xe_lrc {
 
 	/** @fence_ctx: context for hw fence */
 	struct xe_hw_fence_ctx fence_ctx;
+
+	/** @ctx_timestamp: readout value of CTX_TIMESTAMP on last update */
+	u32 ctx_timestamp;
 };
 
 struct xe_lrc_snapshot;
-- 
2.43.0