[PATCH 2/5] csky: Add reg-io-width property for csky pmu

[Mao Han]

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
reg-io-width property from dts.

Signed-off-by: Mao Han <han_...@c-sky.com>
CC: Guo Ren <guo...@kernel.org>
CC: linux-c...@vger.kernel.org
---
 arch/csky/kernel/perf_event.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/csky/kernel/perf_event.c b/arch/csky/kernel/perf_event.c
index c022acc..f1b3cdf 100644
--- a/arch/csky/kernel/perf_event.c
+++ b/arch/csky/kernel/perf_event.c
@@ -18,6 +18,7 @@ static void 
(*hw_raw_write_mapping[CSKY_PMU_MAX_EVENTS])(uint64_t val);
 
 struct csky_pmu_t {
        struct pmu      pmu;
+       uint32_t        sign_extend;
        uint32_t        hpcr;
 } csky_pmu;
 
@@ -806,7 +807,13 @@ 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]();
+       /*
+        * Extend count value to 64bit, otherwise delta calculation would
+        * be incorrect when overflow occurs.
+        */
+       uint64_t new_raw_count = ((int64_t)hw_raw_read_mapping[hwc->idx]()
+                                  << csky_pmu.sign_extend)
+                                  >> csky_pmu.sign_extend;
        int64_t delta = new_raw_count - prev_raw_count;
 
        /*
@@ -1037,6 +1044,7 @@ int csky_pmu_device_probe(struct platform_device *pdev,
        const struct of_device_id *of_id;
        csky_pmu_init init_fn;
        struct device_node *node = pdev->dev.of_node;
+       int cnt_width;
        int ret = -ENODEV;
 
        of_id = of_match_node(of_table, pdev->dev.of_node);
@@ -1045,6 +1053,12 @@ int csky_pmu_device_probe(struct platform_device *pdev,
                ret = init_fn(&csky_pmu);
        }
 
+       if (!of_property_read_u32(node, "reg-io-width", &cnt_width)) {
+               csky_pmu.sign_extend = 64 - cnt_width;
+       } else {
+               csky_pmu.sign_extend = 16;
+       }
+
        if (ret) {
                pr_notice("[perf] failed to probe PMU!\n");
                return ret;
-- 
2.7.4