[PATCH v2] Added perf functionality to mmdc driver

On Tue, Aug 16, 2016 at 08:40:08PM +0000, Zhengyu Shen wrote:

quoted

quoted

quoted

quoted

+	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.

Ok. It would be worth noting this with a comment next to either the
hrtimer handler or registration thereof.

I assume that on overflow the counter wraps rather than saturating?

Thanks,
Mark.