Re: [PATCH v1 03/11] drivers: soc: hisi: Add support for Hisilicon Djtag driver

[Anurup M <anurupvasu@gmail.com>]

On Wednesday 09 November 2016 02:36 PM, John Garry wrote:
>
>>>>> I'd suggest requiring #address-cells=<1> and #size-cells=<0> in the
>>>>> master
>>>>> node, and listing the children by reg property. If the address is not
>>>>> easily expressed as a single integer, use a larger #address-cells
>>>>> value.
>>>> We already have something equivalent to reg in "module-id" (see patch
>>>> 02/11), which is the slave device bus address; here's a sample:
>>>> +        /* For L3 cache PMU */
>>>> +        pmul3c0 {
>>>> +            compatible = "hisilicon,hisi-pmu-l3c-v1";
>>>> +            scl-id = <0x02>;
>>>> +            num-events = <0x16>;
>>>> +            num-counters = <0x08>;
>>>> +            module-id = <0x04>;
>>>> +            num-banks = <0x04>;
>>>> +            cfgen-map = <0x02 0x04 0x01 0x08>;
>>>> +            counter-reg = <0x170>;
>>>> +            evctrl-reg = <0x04>;
>>>> +            event-en = <0x1000000>;
>>>> +            evtype-reg = <0x140>;
>>>> +        };
>>>>
>>>> FYI, "module-id" is our own internal hw nomenclature.
>>> Yes, that was my interpretation as well. Please use the standard
>>> "reg" property for this then.
>> Hi Arnd,
>>
>> Firstly my apologies for a mistake in the bindings example in ([PATCH
>> 02/11 ..]).
>> The module-id property is a list as defined in the PMU bindings patch
>> ([PATCH v1 05/11] dt-bindings .. <https://lkml.org/lkml/2016/11/2/323>).
>>
>> +    djtag0: djtag@0 {
>> +        compatible = "hisilicon,hip05-cpu-djtag-v1";
>> +            pmul3c0 {
>> +                compatible = "hisilicon,hisi-pmu-l3c-v1";
>> +                scl-id = <0x02>;
>> +                num-events = <0x16>;
>> +                num-counters = <0x08>;
>> +                module-id = <0x04 0x04 0x04 0x04>;
>> +                num-banks = <0x04>;
>> +                cfgen-map = <0x02 0x04 0x01 0x08>;
>> +                counter-reg = <0x170>;
>> +                evctrl-reg = <0x04>;
>> +                event-en = <0x1000000>;
>> +                evtype-reg = <0x140>;
>> +            };
>>
>>
>> The L3 cache in hip05/06/07 chips consist of 4 banks (each bank has PMU
>> registers).
>>
>> In hip05/06 all L3 cache banks are identified with same module-id.
>> module-id = <0x04 0x04 0x04 0x04>;
>>
>> But in the case hip07 chip(djtag v2), each L3 cache bank has different
>> module-id
>> module-id = <0x01 0x02 0x03 0x04>;
>>
>> So in this case Please share your opinion on how to model it.
>>
>
> My suggestion is to have a single PMU per module, whether that is 4 
> banks or 1 bank per module, as this makes the driver simpler.
>
> I think you mentioned that a separate PMU per bank does not make much 
> sense, and you would rather treat all banks as a single bank and 
> aggregrate their perf statstics under a single PMU: Can you just use a 
> script in userspace which can do this aggregration work if you have 
> separate PMUs?
Hi John,

Mark also suggest the same view.
I have some concerns or doubts in having separate PMU for each L3 cache 
bank.
We can discuss it in the same thread [[RESEND PATCH v1 07/11]] 
<http://www.spinics.net/lists/arm-kernel/msg541938.html>].

Thanks,
Anurup
>
> Maybe perf guys have a view on this also.
>
> John
>
>> Some more detail of L3 cache PMU.
>> ------------------------------------------------
>> The hip05/06/07 chips consists of a multiple Super CPU cluster (16 CPU
>> cores). we call it SCCL.
>> The L3 cache( 4 banks) is shared by all CPU cores in a SCCL.
>> Each L3 cache bank has PMU registers. We always take the sum of the
>> counters to show in perf.
>> Taking individual L3 cache count is not meaningful as there is no
>> mapping of CPU cores to individual
>> L3 cache banks.
>>
>> Please share your suggestion.
>>
>> Thanks,
>> Anurup
>