From 4fc9355c0d037c7ff98188ff66a00abf41104ee9 Mon Sep 17 00:00:00 2001
From: Robert Richter <robert.richter@amd.com>
Date: Mon, 2 Apr 2012 20:19:10 +0200
Subject: [PATCH] --- yaml --- r: 304886 b: refs/heads/master c:
 6accb9cf76080422d400a641d9068b6b2a2c216f h: refs/heads/master v: v3

---
 [refs]                                         |  2 +-
 trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c | 18 ++++++++++++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index 79bc08c65a89..e7afc2178fa2 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7bf352384fda3f678a283928c6c5b2cd9da877e4
+refs/heads/master: 6accb9cf76080422d400a641d9068b6b2a2c216f
diff --git a/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index ebf169fe40ef..bc401bd9f14a 100644
--- a/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/trunk/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -162,9 +162,16 @@ static int perf_ibs_init(struct perf_event *event)
 		if (config & perf_ibs->cnt_mask)
 			/* raw max_cnt may not be set */
 			return -EINVAL;
-		if (hwc->sample_period & 0x0f)
-			/* lower 4 bits can not be set in ibs max cnt */
+		if (!event->attr.sample_freq && hwc->sample_period & 0x0f)
+			/*
+			 * lower 4 bits can not be set in ibs max cnt,
+			 * but allowing it in case we adjust the
+			 * sample period to set a frequency.
+			 */
 			return -EINVAL;
+		hwc->sample_period &= ~0x0FULL;
+		if (!hwc->sample_period)
+			hwc->sample_period = 0x10;
 	} else {
 		max_cnt = config & perf_ibs->cnt_mask;
 		config &= ~perf_ibs->cnt_mask;
@@ -175,6 +182,13 @@ static int perf_ibs_init(struct perf_event *event)
 	if (!hwc->sample_period)
 		return -EINVAL;
 
+	/*
+	 * If we modify hwc->sample_period, we also need to update
+	 * hwc->last_period and hwc->period_left.
+	 */
+	hwc->last_period = hwc->sample_period;
+	local64_set(&hwc->period_left, hwc->sample_period);
+
 	hwc->config_base = perf_ibs->msr;
 	hwc->config = config;