| Message ID | 20240829090332.28756-2-yangyicong@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Some updates for HiSilicon PCIe PMU | expand |
On Thu, 29 Aug 2024 17:03:30 +0800 Yicong Yang <yangyicong@huawei.com> wrote: > From: Yicong Yang <yangyicong@hisilicon.com> > > Currently we set the period and record it as the initial value of the > counter without checking it's set to the hardware successfully or not. > However the counter maybe unwritable if the target event is unsupported > by the device. In such case we will pass user a wrong count: > > [start counts when setting the period] > hwc->prev_count = 0x8000000000000000 > device.counter_value = 0 // the counter is not set as the period > [when user reads the counter] > event->count = device.counter_value - hwc->prev_count > = 0x8000000000000000 // wrong. should be 0. > > Fix this by record the hardware counter counts correctly when setting > the period. > > Fixes: 8404b0fbc7fb ("drivers/perf: hisi: Add driver for HiSilicon PCIe PMU") > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
diff --git a/drivers/perf/hisilicon/hisi_pcie_pmu.c b/drivers/perf/hisilicon/hisi_pcie_pmu.c index f06027574a24..fba569a8640c 100644 --- a/drivers/perf/hisilicon/hisi_pcie_pmu.c +++ b/drivers/perf/hisilicon/hisi_pcie_pmu.c @@ -452,10 +452,24 @@ static void hisi_pcie_pmu_set_period(struct perf_event *event) struct hisi_pcie_pmu *pcie_pmu = to_pcie_pmu(event->pmu); struct hw_perf_event *hwc = &event->hw; int idx = hwc->idx; + u64 orig_cnt, cnt; + + orig_cnt = hisi_pcie_pmu_read_counter(event); local64_set(&hwc->prev_count, HISI_PCIE_INIT_VAL); hisi_pcie_pmu_writeq(pcie_pmu, HISI_PCIE_CNT, idx, HISI_PCIE_INIT_VAL); hisi_pcie_pmu_writeq(pcie_pmu, HISI_PCIE_EXT_CNT, idx, HISI_PCIE_INIT_VAL); + + /* + * The counter maybe unwritable if the target event is unsupported. + * Check this by comparing the counts after setting the period. If + * the counts stay unchanged after setting the period then update + * the hwc->prev_count correctly. Otherwise the final counts user + * get maybe totally wrong. + */ + cnt = hisi_pcie_pmu_read_counter(event); + if (orig_cnt == cnt) + local64_set(&hwc->prev_count, cnt); } static void hisi_pcie_pmu_enable_counter(struct hisi_pcie_pmu *pcie_pmu, struct hw_perf_event *hwc)