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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 V5 2/6] csky: Add count-width property for csky pmu
Date:   Tue,  4 Jun 2019 18:54:45 +0800
Message-Id: <93df91a6bdd2fe46dcf71fdd996fa1e164a8adf4.1559644961.git.han_mao@c-sky.com>
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References: <cover.1559644961.git.han_mao@c-sky.com>
In-Reply-To: <cover.1559644961.git.han_mao@c-sky.com>
References: <cover.1559644961.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 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/csky/kernel/perf_event.c b/arch/csky/kernel/perf_event.c
index 2282554..a15b397 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;
 
@@ -804,7 +806,12 @@ 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 - 1);
 	int64_t delta = new_raw_count - prev_raw_count;
 
 	/*
@@ -1032,6 +1039,7 @@ int init_hw_perf_events(void)
 int csky_pmu_device_probe(struct platform_device *pdev,
 			  const struct of_device_id *of_table)
 {
+	struct device_node *node = pdev->dev.of_node;
 	int ret;
 
 	ret = init_hw_perf_events();
@@ -1040,6 +1048,11 @@ int csky_pmu_device_probe(struct platform_device *pdev,
 		return ret;
 	}
 
+	if (of_property_read_u32(node, "count-width",
+				 &csky_pmu.count_width)) {
+		csky_pmu.count_width = DEFAULT_COUNT_WIDTH;
+	}
+
 	return ret;
 }
 
-- 
2.7.4