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From:   Mao Han <han_mao@c-sky.com>
To:     linux-kernel@vger.kernel.org
Cc:     Mao Han <han_mao@c-sky.com>, linux-csky@vger.kernel.org,
        Guo Ren <guoren@kernel.org>
Subject: [PATCH V4 2/6] csky: Add count-width property for csky pmu
Date:   Tue,  4 Jun 2019 10:23:56 +0800
Message-Id: <d38f72230b838419a1ef829dcb27373807d697b5.1559614824.git.han_mao@c-sky.com>
In-Reply-To: <cover.1559614824.git.han_mao@c-sky.com>
References: <cover.1559614824.git.han_mao@c-sky.com>
In-Reply-To: <cover.1559614824.git.han_mao@c-sky.com>
References: <cover.1559614824.git.han_mao@c-sky.com>
Sender: linux-kernel-owner@vger.kernel.org
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The csky pmu counter may have different io width. When the counter is
smaller then 64 bits and counter value is smaller than the old value, it
will result to a extremely large delta value. So the sampled value should
be extend to 64 bits to avoid this, the extension bits base on the
count-width property from dts.

Signed-off-by: Mao Han <han_mao@c-sky.com>
Cc: Guo Ren <guoren@kernel.org>
---
 arch/csky/kernel/perf_event.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/csky/kernel/perf_event.c b/arch/csky/kernel/perf_event.c
index c022acc..36f7f20 100644
--- a/arch/csky/kernel/perf_event.c
+++ b/arch/csky/kernel/perf_event.c
@@ -9,6 +9,7 @@
 #include <linux/platform_device.h>
 
 #define CSKY_PMU_MAX_EVENTS 32
+#define DEFAULT_COUNT_WIDTH 48
 
 #define HPCR		"<0, 0x0>"	/* PMU Control reg */
 #define HPCNTENR	"<0, 0x4>"	/* Count Enable reg */
@@ -18,6 +19,7 @@ static void (*hw_raw_write_mapping[CSKY_PMU_MAX_EVENTS])(uint64_t val);
 
 struct csky_pmu_t {
 	struct pmu	pmu;
+	uint32_t	count_width;
 	uint32_t	hpcr;
 } csky_pmu;
 
@@ -806,7 +808,12 @@ static void csky_perf_event_update(struct perf_event *event,
 				   struct hw_perf_event *hwc)
 {
 	uint64_t prev_raw_count = local64_read(&hwc->prev_count);
-	uint64_t new_raw_count = hw_raw_read_mapping[hwc->idx]();
+	/*
+	 * Sign extend count value to 64bit, otherwise delta calculation
+	 * would be incorrect when overflow occurs.
+	 */
+	uint64_t new_raw_count = sign_extend64(
+			hw_raw_read_mapping[hwc->idx](), csky_pmu.count_width);
 	int64_t delta = new_raw_count - prev_raw_count;
 
 	/*
@@ -1045,6 +1052,11 @@ int csky_pmu_device_probe(struct platform_device *pdev,
 		ret = init_fn(&csky_pmu);
 	}
 
+	if (!of_property_read_u32(node, "count-width",
+				  &csky_pmu.count_width)) {
+		csky_pmu.count_width = DEFAULT_COUNT_WIDTH;
+	}
+
 	if (ret) {
 		pr_notice("[perf] failed to probe PMU!\n");
 		return ret;
-- 
2.7.4