[Intel-gfx] [PATCH 3/3] i915/perf: Drop the aged_tail from rewind logic

[Umesh Nerlige Ramappa]

Instead of aged_tail use an iterator that starts from the hw_tail and
goes backward until the oa_buffer.tail looking for valid reports.

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
---
 drivers/gpu/drm/i915/i915_perf.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index beb1269422ca..39f5ab1911c8 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -543,7 +543,7 @@ static bool oa_buffer_check_unlocked(struct i915_perf_stream *stream)
 {
 	u32 gtt_offset = i915_ggtt_offset(stream->oa_buffer.vma);
 	int report_size = stream->oa_buffer.format->size;
-	u32 head, tail, aged_tail;
+	u32 head, tail, iter;
 	unsigned long flags;
 	bool pollin;
 	u32 hw_tail;
@@ -567,15 +567,14 @@ static bool oa_buffer_check_unlocked(struct i915_perf_stream *stream)
 	/* Subtract partial amount off the tail */
 	hw_tail = OA_TAKEN(hw_tail, partial_report_size);
 
-
 	/* NB: The head we observe here might effectively be a little
 	 * out of date. If a read() is in progress, the head could be
 	 * anywhere between this head and stream->oa_buffer.tail.
 	 */
 	head = stream->oa_buffer.head - gtt_offset;
-	aged_tail = stream->oa_buffer.tail - gtt_offset;
+	tail = stream->oa_buffer.tail - gtt_offset;
 
-	tail = hw_tail;
+	iter = hw_tail;
 
 		/* Walk the stream backward until we find a report with report
 		 * id and timestmap not at 0. Since the circular buffer pointers
@@ -588,23 +587,23 @@ static bool oa_buffer_check_unlocked(struct i915_perf_stream *stream)
 	 * memory in the order they were written to.
 	 * If not : (╯°□°）╯︵ ┻━┻
 	 */
-	while (OA_TAKEN(tail, aged_tail) >= report_size) {
-		void *report = stream->oa_buffer.vaddr + tail;
+	while (OA_TAKEN(iter, tail) >= report_size) {
+		void *report = stream->oa_buffer.vaddr + iter;
 
 		if (oa_report_id(stream, report) ||
 		    oa_timestamp(stream, report))
 			break;
 
-		tail = (tail - report_size) & (OA_BUFFER_SIZE - 1);
+		iter = (iter - report_size) & (OA_BUFFER_SIZE - 1);
 	}
 
-	if (OA_TAKEN(hw_tail, tail) > report_size &&
+	if (OA_TAKEN(hw_tail, iter) > report_size &&
 	    __ratelimit(&stream->perf->tail_pointer_race))
 		drm_notice(&stream->uncore->i915->drm,
 			   "unlanded report(s) head=0x%x tail=0x%x hw_tail=0x%x\n",
 		 head, tail, hw_tail);
 
-	stream->oa_buffer.tail = gtt_offset + tail;
+	stream->oa_buffer.tail = gtt_offset + iter;
 
 	pollin = OA_TAKEN(stream->oa_buffer.tail - gtt_offset,
 			  stream->oa_buffer.head - gtt_offset) >= report_size;
-- 
2.36.1