RE: [PATCH v2] Added perf functionality to mmdc driver

From	Zhengyu Shen <zhengyu.shen@nxp.com>
Newsgroups	linux.kernel
Subject	RE: [PATCH v2] Added perf functionality to mmdc driver
Date	2016-08-16 19:20 +0200
Message-ID	<s6NQK-4jo-15@gated-at.bofh.it> (permalink)
References	<s6Aqt-4jk-5@gated-at.bofh.it> <s6K6u-1XD-15@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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> > 	Added cpumask and migration handling support to driver
> > 	Validated event during event_init
> > 	Added code to properly stop counters
> > 	Used perf_invalid_context instead of perf_sw_context
> > 	Added hrtimer to poll for overflow
> > 	Added better description
> > 	Added support for multiple mmdcs
> 
> As I commented on v1 w.r.t. the above, I would appreciate being Cc'd on
> future versions of this patch.

Sorry about that, I'll be sure to CC you in the future. 

> > +static void mmdc_event_start(struct perf_event *event, int flags) {
> > +	struct mmdc_pmu *pmu_mmdc = to_mmdc_pmu(event->pmu);
> > +	void __iomem *mmdc_base, *reg;
> > +
> > +	local64_set(&event->count, 0);
> > +	mmdc_base = pmu_mmdc->mmdc_base;
> > +	reg = mmdc_base + MMDC_MADPCR0;
> > +	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. 

Thanks a lot for the feedback!

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Re: [PATCH v2] Added perf functionality to mmdc driver Mark Rutland <mark.rutland@arm.com> - 2016-08-16 12:50 +0200
  Re: [PATCH v2] Added perf functionality to mmdc driver Peter Zijlstra <peterz@infradead.org> - 2016-08-16 14:10 +0200
  Re: [PATCH v2] Added perf functionality to mmdc driver Mark Rutland <mark.rutland@arm.com> - 2016-08-16 16:50 +0200
    RE: [PATCH v2] Added perf functionality to mmdc driver Zhengyu Shen <zhengyu.shen@nxp.com> - 2016-08-17 07:20 +0200
      Re: [PATCH v2] Added perf functionality to mmdc driver Mark Rutland <mark.rutland@arm.com> - 2016-08-17 12:10 +0200
  RE: [PATCH v2] Added perf functionality to mmdc driver Zhengyu Shen <zhengyu.shen@nxp.com> - 2016-08-16 19:20 +0200

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