[PATCH V4 2/6] csky: Add count-width property for csky pmu

[Mao Han]

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_...@c-sky.com>
Cc: Guo Ren <guo...@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