linux-kernel - Re: [PATCH v5 3/6] perf: hisi: Add support for HiSilicon SoC L3C PMU driver

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Date:   Wed, 18 Oct 2017 22:08:15 +0800
From:   Zhangshaokun <zhangshaokun@...ilicon.com>
To:     Mark Rutland <mark.rutland@....com>
CC:     <will.deacon@....com>, <jonathan.cameron@...wei.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linuxarm@...wei.com>, Anurup M <anurup.m@...wei.com>
Subject: Re: [PATCH v5 3/6] perf: hisi: Add support for HiSilicon SoC L3C PMU
 driver

Hi Mark,

Thanks for your further explanation.

On 2017/10/18 21:55, Mark Rutland wrote:
> On Wed, Oct 18, 2017 at 09:33:30PM +0800, Zhangshaokun wrote:
>> On 2017/10/17 23:16, Mark Rutland wrote:
>>> On Tue, Aug 22, 2017 at 04:07:54PM +0800, Shaokun Zhang wrote:
>>>> +static int hisi_l3c_pmu_init_data(struct platform_device *pdev,
>>>> +				  struct hisi_pmu *l3c_pmu)
>>>> +{
>>>> +	unsigned long long id;
>>>> +	struct resource *res;
>>>> +	acpi_status status;
>>>> +	int cpu;
>>>> +
>>>> +	status = acpi_evaluate_integer(ACPI_HANDLE(&pdev->dev),
>>>> +				       "_UID", NULL, &id);
>>>> +	if (ACPI_FAILURE(status))
>>>> +		return -EINVAL;
>>>> +
>>>> +	l3c_pmu->id = id;
>>>> +
>>>> +	/*
>>>> +	 * Use the SCCL_ID and CCL_ID to identify the L3C PMU, while
>>>> +	 * SCCL_ID is in MPIDR[aff2] and CCL_ID is in MPIDR[aff1].
>>>> +	 */
>>>> +	if (device_property_read_u32(&pdev->dev, "hisilicon,scl-id",
>>>> +				     &l3c_pmu->sccl_id)) {
>>>> +		dev_err(&pdev->dev, "Can not read l3c sccl-id!\n");
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	if (device_property_read_u32(&pdev->dev, "hisilicon,ccl-id",
>>>> +				     &l3c_pmu->ccl_id)) {
>>>> +		dev_err(&pdev->dev, "Can not read l3c ccl-id!\n");
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	/* Initialise the associated cpumask of the PMU */
>>>> +	for_each_present_cpu(cpu)
>>>> +		smp_call_function_single(cpu, hisi_l3c_pmu_set_cpumask_by_ccl,
>>>> +					 (void *)l3c_pmu, 1);
> 
>>> Rather than a proble-time smp_call_function_single(), can you follow the
>>> qcom l2's approach of associating CPUs with a PMU instance in the
>>> notifier? That will work even if CPUs are brought online very late.
>>
>> A good guidance, but HHA and DDRC PMUs are different from L3C PMU, the former
>> share the same SCCL and the latter share the same SCCL and CCL. I will
>> try to deal with this difference in online notifier.
> 
> FWIW, I think it makes sense for each PMU to have its own notifier
> (perhaps with some shared code that each calls to do the migration).
> 
> I just want to avoid the smp_call_function_single() at probe time, as
> that doesn't work in some cases.
> 

Got it, i shall update the hisi_pmu::associated_cpus only in online
and offline notifiers.

Thanks,
Shaokun

> Thanks,
> Mark.
> 
> .
>