Messages in this thread | | | From | Zhengyu Shen <> | Subject | RE: [PATCH v2] Added perf functionality to mmdc driver | Date | Tue, 16 Aug 2016 20:40:08 +0000 |
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> > > > + hrtimer_start(&pmu_mmdc->hrtimer, mmdc_timer_period(), > > > > + HRTIMER_MODE_REL_PINNED); > > > > > > Why is a hrtimer necessary? Is this just copy-pasted from CCN, or do > > > you have similar HW issues? > > > > > > Is there no overflow interrupt? > > > > When overflow occurs, a register bit is set to one. There is no > > overflow interrupt which is why the timer is needed. > > I see. Please have add comment in the driver explaining this, so that this is > obvious. > > Does the counter itself wrap and continue counting, or does it saturate? > > How have you tuned your polling period so as to avoid missing events in the > case of an overflow? > > Thanks, > Mark. The counter wraps around once every ten seconds for total-cycles (which is the Fastest increasing counter). Polling is done every one second just to be safe.
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