From 8b44e453478ac28fb93db18941f887ca691a54ea Mon Sep 17 00:00:00 2001
From: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Date: Fri, 19 Feb 2021 22:10:33 +0200
Subject: [PATCH] intel/perf: fix roll over PERF_CNT counter accumulation
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Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: 5ba6d9941b5dda ("intel/perf: add mdapi writes for register perf counters")
Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9163>
---
 src/intel/perf/gen_perf.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/intel/perf/gen_perf.c b/src/intel/perf/gen_perf.c
index 23a5465..795aa88 100644
--- a/src/intel/perf/gen_perf.c
+++ b/src/intel/perf/gen_perf.c
@@ -1144,8 +1144,12 @@ gen_perf_query_result_read_perfcnts(struct gen_perf_query_result *result,
                                     const uint64_t *end)
 {
    for (uint32_t i = 0; i < 2; i++) {
-      result->accumulator[query->perfcnt_offset + i] =
-         (end[i] & PERF_CNT_VALUE_MASK) - (start[i] & PERF_CNT_VALUE_MASK);
+      uint64_t v0 = start[i] & PERF_CNT_VALUE_MASK;
+      uint64_t v1 = end[i] & PERF_CNT_VALUE_MASK;
+
+      result->accumulator[query->perfcnt_offset + i] = v0 > v1 ?
+         (PERF_CNT_VALUE_MASK + 1 + v1 - v0) :
+         (v1 - v0);
    }
 }
 
-- 
2.7.4