linux-kernel - Re: [PATCH v5 05/11] arm-cci PMU: Delay counter writes to pmu

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Message-ID: <56938D2B.7050700@arm.com>
Date:	Mon, 11 Jan 2016 11:08:27 +0000
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	arm@...nel.org, punit.agrawal@....com, peterz@...radead.org
Subject: Re: [PATCH v5 05/11] arm-cci PMU: Delay counter writes to pmu_enable

On 11/01/16 10:46, Mark Rutland wrote:
> On Tue, Jan 05, 2016 at 09:59:13AM +0000, Suzuki K. Poulose wrote:
>> On 04/01/16 19:24, Mark Rutland wrote:
>>> On Mon, Jan 04, 2016 at 11:54:44AM +0000, Suzuki K. Poulose wrote:
>> The pmu is not disabled while we are in overflow irq handler. Hence there may
>> not be a pmu_enable() which would set the period for the counter which
>> overflowed, if defer the write in that case. Is that assumption wrong ?
>
> As the driver stands today, yes.
>
> However, wouldn't it make more sense to disable the PMU for the overflow
> handler, such that we can reuse the batching logic?

None of the PMU drivers do that AFAIK. Hence, didn't want to change it for
CCI. We could use the batching logic, if decide to do so. I can go ahead
with that if there are no other side effects with that.

Suzuki