From: Suzuki.Poulose@arm•com (Suzuki K. Poulose)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5 03/11] arm-cci: Group writes to counter
Date: Mon, 11 Jan 2016 10:48:23 +0000 [thread overview]
Message-ID: <56938877.4060103@arm.com> (raw)
In-Reply-To: <20160111104407.GD6499@leverpostej>
On 11/01/16 10:44, Mark Rutland wrote:
> On Tue, Jan 05, 2016 at 10:51:47AM +0000, Suzuki K. Poulose wrote:
>> On 04/01/16 19:03, Mark Rutland wrote:
>>> On Mon, Jan 04, 2016 at 11:54:42AM +0000, Suzuki K. Poulose wrote:
>>>> Add a helper to group the writes to PMU counter, this will be
>>>> used to delay setting the event period to pmu::pmu_enable()
>>>>
>>
>>>> +/* Write a value to a given set of counters */
>>>> +static void __pmu_write_counters(struct cci_pmu *cci_pmu, unsigned long *mask, u32 value)
>>>> +{
>>>> + int i;
>>>> +
>>>> + for_each_set_bit(i, mask, cci_pmu->num_cntrs)
>>>> + __pmu_write_counter(cci_pmu, value, i);
>>>> +}
>>>
>>> I don't understand this as-is. Why do all the counters have the same
>>> value?
>>
>> The only value we write to the counters is the period. This routine writes
>> a given value to a set of counters specified by the mask (not to be confused
>> with the PMU->hw_events->mask). This will help to group the writes to the counters,
>> especially since preparatory steps to write to a single counter itself is costly.
>> So, we do all the preparation only once for a batch of counters.
>>
>> The other option is to use hw_events->prev_count (which should be set before calling
>> the function) for each counter specified in the mask. I am fine with either of the
>> two.
>
> I think this would be clearer using prev_count.
>
> I guess it doesn't matter since we won't support sampling, but it would
> match the shape of other PMU drivers.
OK, will use that.
Thanks
Suzuki
next prev parent reply other threads:[~2016-01-11 10:48 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-04 11:54 [PATCH v5 00/11] arm-cci: PMU updates Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 01/11] arm-cci: Define CCI counter period Suzuki K. Poulose
2016-01-04 18:27 ` Mark Rutland
2016-01-05 9:50 ` Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 02/11] arm-cci: Refactor pmu_write_counter Suzuki K. Poulose
2016-01-04 19:01 ` Mark Rutland
2016-01-04 11:54 ` [PATCH v5 03/11] arm-cci: Group writes to counter Suzuki K. Poulose
2016-01-04 19:03 ` Mark Rutland
2016-01-05 10:51 ` Suzuki K. Poulose
2016-01-11 10:44 ` Mark Rutland
2016-01-11 10:48 ` Suzuki K. Poulose [this message]
2016-01-04 11:54 ` [PATCH v5 04/11] arm-cci: Refactor CCI PMU enable/disable methods Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 05/11] arm-cci PMU: Delay counter writes to pmu_enable Suzuki K. Poulose
2016-01-04 19:24 ` Mark Rutland
2016-01-05 9:59 ` Suzuki K. Poulose
2016-01-11 10:46 ` Mark Rutland
2016-01-11 11:08 ` Suzuki K. Poulose
2016-01-11 11:24 ` Mark Rutland
2016-01-11 18:12 ` Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 06/11] arm-cci: Get the status of a counter Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 07/11] arm-cci: Add routines to save/restore all counters Suzuki K. Poulose
2016-01-11 10:50 ` Mark Rutland
2016-01-11 10:58 ` Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 08/11] arm-cci: Provide hook for writing to PMU counters Suzuki K. Poulose
2016-01-11 10:54 ` Mark Rutland
2016-01-11 12:14 ` Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 09/11] arm-cci: CCI-500: Work around PMU counter writes Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 10/11] arm-cci500: Rearrange PMU driver for code sharing with CCI-550 PMU Suzuki K. Poulose
2016-01-04 11:54 ` [PATCH v5 11/11] arm-cci: CoreLink CCI-550 PMU driver Suzuki K. Poulose
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