linux-kernel - [PATCH 7/9] metag: perf: don't reset TXTACTCYC

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Date:	Fri, 15 Mar 2013 13:43:46 +0000
From:	James Hogan <james.hogan@...tec.com>
To:	<linux-kernel@...r.kernel.org>
CC:	James Hogan <james.hogan@...tec.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: [PATCH 7/9] metag: perf: don't reset TXTACTCYC

The thread active cycle counter TXTACTCYC is used in __delay so it
shouldn't really be reset to zero by perf. Fix perf to just read the
value, and instead of clearing it, record the prev_count value in
enable_counter so that the delta calculations know about the previous
value.

Signed-off-by: James Hogan <james.hogan@...tec.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
---
 arch/metag/kernel/perf/perf_event.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/metag/kernel/perf/perf_event.c b/arch/metag/kernel/perf/perf_event.c
index 54fde35..a1eff36 100644
--- a/arch/metag/kernel/perf/perf_event.c
+++ b/arch/metag/kernel/perf/perf_event.c
@@ -617,9 +617,7 @@ static void metag_pmu_enable_counter(struct hw_perf_event *event, int idx)
 		WARN_ONCE((config != 0x100),
 			"invalid configuration (%d) for counter (%d)\n",
 			config, idx);
-
-		/* Reset the cycle count */
-		__core_reg_set(TXTACTCYC, 0);
+		local64_set(&event->prev_count, __core_reg_get(TXTACTCYC));
 		goto unlock;
 	}
 
@@ -708,9 +706,8 @@ static u64 metag_pmu_read_counter(int idx)
 {
 	u32 tmp = 0;
 
-	/* The act of reading the cycle counter also clears it */
 	if (METAG_INST_COUNTER == idx) {
-		__core_reg_swap(TXTACTCYC, tmp);
+		tmp = __core_reg_get(TXTACTCYC);
 		goto out;
 	}
 
-- 
1.8.1.2


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