linux-kernel - Re: [PATCH 1/2] ARM: dts: imx6q: add pmu interrupt-affinity

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Date:   Fri, 18 Jan 2019 16:41:50 +0100
From:   Stefan Agner <stefan@...er.ch>
To:     Lucas Stach <l.stach@...gutronix.de>
Cc:     shawnguo@...nel.org, s.hauer@...gutronix.de,
        max.krummenacher@...adex.com, marcel.ziswiler@...adex.com,
        linux-kernel@...r.kernel.org, linux-imx@....com,
        kernel@...gutronix.de, fabio.estevam@....com, dev@...henker.ch,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] ARM: dts: imx6q: add pmu interrupt-affinity

On 18.01.2019 15:12, Lucas Stach wrote:
> Am Freitag, den 18.01.2019, 14:59 +0100 schrieb Stefan Agner:
>> Explicitly specify interrupt affinity to avoid HW perfevents
>> need to guess. This avoids the following error upon boot:
>>   hw perfevents: no interrupt-affinity property for /pmu, guessing.
>>
> But then it isn't correct either AFAICS. On i.MX6 all the PMU IRQs are
> ORed together into a single SPI, instead of each core dealing with its
> own PPI. So pretending that there are more IRQs with affinity to each
> core isn't the right thing to do, no?
> 

Oh I see, we only have a single interrupt in the i.MX 6 case.

I agree, this patches are wrong.

Hm, but why does hw perf then think it needs to guess? Doesn't seem hard
to guess right if there is only one choice...

We probably need to do something like this?

--- a/drivers/perf/arm_pmu_platform.c
+++ b/drivers/perf/arm_pmu_platform.c
@@ -122,7 +122,8 @@ static int pmu_parse_irqs(struct arm_pmu *pmu)
                        return pmu_parse_percpu_irq(pmu, irq);
        }
 
-       if (nr_cpu_ids != 1 && !pmu_has_irq_affinity(pdev->dev.of_node))
{
+       if ((nr_cpu_ids != 1 || num_irqs != 1) &&
+           !pmu_has_irq_affinity(pdev->dev.of_node)) {
                pr_warn("no interrupt-affinity property for %pOF,
guessing.\n",
                        pdev->dev.of_node);
        }

--
Stefan



> Regards,
> Lucas
> 
>> Specifying all four CPUs shows no aversive effects on i.MX 6Dual
>> SoCs.
>>
>> > Signed-off-by: Stefan Agner <stefan@...er.ch>
>> ---
>>  arch/arm/boot/dts/imx6q.dtsi | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/arm/boot/dts/imx6q.dtsi b/arch/arm/boot/dts/imx6q.dtsi
>> index 8381d24eff7d..d2c1977c8b16 100644
>> --- a/arch/arm/boot/dts/imx6q.dtsi
>> +++ b/arch/arm/boot/dts/imx6q.dtsi
>> @@ -537,6 +537,13 @@
>> >  			<0x28 0x0000000c>; /* DCIC2_MUX_CTL */
>>  };
>>  
>> +&pmu {
>> > > +	interrupt-affinity = <&{/cpus/cpu@0}>,
>> > > +			     <&{/cpus/cpu@1}>,
>> > > +			     <&{/cpus/cpu@2}>,
>> > > +			     <&{/cpus/cpu@3}>;
>> +};
>> +
>>  &vpu {
>> >  	compatible = "fsl,imx6q-vpu", "cnm,coda960";
>>  };