Re: [PATCH] drivers/perf: hisi: update the sccl_id/ccl_id for certain HiSilicon platform

From: Shaokun Zhang <zhangshaokun@hisilicon.com>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	John Garry <john.garry@huawei.com>,
	linux-arm-kernel@lists.infradead.org,
	Hanjun Guo <guohanjun@huawei.com>
Subject: Re: [PATCH] drivers/perf: hisi: update the sccl_id/ccl_id for certain HiSilicon platform
Date: Fri, 8 Nov 2019 09:28:44 +0800	[thread overview]
Message-ID: <f2e329c9-11d1-0f47-5392-dc2a067af084@hisilicon.com> (raw)
In-Reply-To: <20191107114041.GB11587@willie-the-truck>

Hi Will,

On 2019/11/7 19:40, Will Deacon wrote:
> Hi,
> 
> On Thu, Nov 07, 2019 at 03:56:04PM +0800, Shaokun Zhang wrote:
>> @@ -338,8 +339,10 @@ void hisi_uncore_pmu_disable(struct pmu *pmu)
>>  
>>  /*
>>   * Read Super CPU cluster and CPU cluster ID from MPIDR_EL1.
>> - * If multi-threading is supported, CCL_ID is the low 3-bits in MPIDR[Aff2]
>> - * and SCCL_ID is the upper 5-bits of Aff2 field; if not, SCCL_ID
>> + * If multi-threading is supported, On Huawei Kunpeng 920 SoC whose cpu
>> + * core is tsv110, CCL_ID is the low 3-bits in MPIDR[Aff2] and SCCL_ID
>> + * is the upper 5-bits of Aff2 field; while for other cpu types, SCCL_ID
>> + * is in MPIDR[Aff3] and CCL_ID is in MPIDR[Aff2], if not, SCCL_ID
>>   * is in MPIDR[Aff2] and CCL_ID is in MPIDR[Aff1].
>>   */
>>  static void hisi_read_sccl_and_ccl_id(int *sccl_id, int *ccl_id)
>> @@ -347,12 +350,19 @@ static void hisi_read_sccl_and_ccl_id(int *sccl_id, int *ccl_id)
>>  	u64 mpidr = read_cpuid_mpidr();
>>  
>>  	if (mpidr & MPIDR_MT_BITMASK) {
>> -		int aff2 = MPIDR_AFFINITY_LEVEL(mpidr, 2);
>> -
>> -		if (sccl_id)
>> -			*sccl_id = aff2 >> 3;
>> -		if (ccl_id)
>> -			*ccl_id = aff2 & 0x7;
>> +		if (read_cpuid_part_number() == HISI_CPU_PART_TSV110) {
>> +			int aff2 = MPIDR_AFFINITY_LEVEL(mpidr, 2);
>> +
>> +			if (sccl_id)
>> +				*sccl_id = aff2 >> 3;
>> +			if (ccl_id)
>> +				*ccl_id = aff2 & 0x7;
>> +		} else {
>> +			if (sccl_id)
>> +				*sccl_id = MPIDR_AFFINITY_LEVEL(mpidr, 3);
>> +			if (ccl_id)
>> +				*ccl_id = MPIDR_AFFINITY_LEVEL(mpidr, 2);
>> +		}
> 
> [I prefer Mark's version, so please reply to indicate whether or not it
>  works for you]
> 
> So I'll take this, but the lesson here seems to be that it's a terrible idea
> to infer system topology from CPU ID registers. In future, I'm going to
> insist that this comes from firmware tables because hacks like the above are

My bad, I shall do it in future.

Thanks,
Shaokun

> not sustainable.
> 
> Will
> 
> .
> 

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