Re: [PATCH V4 0/5] arm_scmi: vendors: Qualcomm Generic Vendor Extensions

[Sibi Sankar <quic_sibis@quicinc.com>]

On 12/19/24 16:07, Johan Hovold wrote:
> On Tue, Dec 17, 2024 at 05:19:25PM +0530, Sibi Sankar wrote:
>> On 12/5/24 21:22, Johan Hovold wrote:
>>> On Thu, Dec 05, 2024 at 04:26:55PM +0530, Sibi Sankar wrote:
>>>> On 11/22/24 14:07, Johan Hovold wrote:
>>>
>>>>> I have a Lenovo ThinkPad T14s set up now so I gave this series a spin
>>>>> there too, and there I do *not* see the above mentioned -EOPNOSUPP error
>>>>> and the memlat driver probes successfully.
>>>>>
>>>>> On the other hand, this series seems to have no effect on a kernel
>>>>> compilation benchmark. Is that expected?
>>>>
>>>> I can have a look at your tree. But memlat in general
>>>> depends on the cpu frequency when your benchmarks max
>>>> the cpu's the ddr/llcc are scaled accordingly by it.
>>>
>>> A kernel compilation should max out the CPU frequency on all cores.
> 
> Answering my own question here; bwmon should scale the buses for
> benchmarks like kernel compilations so I guess the non-existing impact
> of memlat is expected here.

you would see impact only in cases where you would benefit from
having ddr and llcc at a higher frequency i.e. latency workloads.
I usually run geekbench with and we are expected to see a big
difference with and without it.

> 
> Ettore helped me run some further benchmarks, including cachebench, but
> also saw no positive (or negative) effect with this series running on an
> X1E CRD (with recent firmware).
> 
> Do you have any suggestions of benchmarks to run where the effect of
> memlat should show up? What have you been using for testing?
> 
> I did measure a possibly slightly higher (idle) power consumption with
> memlat, but I guess that is also expected given the intended more
> aggressive ramping of the bus clocks.
> 
> These are the branches (and configs; johan_defconfig) we've used for
> testing:
> 
> 	https://github.com/jhovold/linux/tree/wip/x1e80100-6.13-rc3
> 	https://github.com/jhovold/linux/tree/wip/x1e80100-6.13-rc3-memlat

Thanks, we'll get this sorted out.

> 
>>>>> And does this mean that you should stick with the uppercase "MEMLAT"
>>>>> string after all? The firmware on my CRD is not the latest one, but I am
>>>>> using the latest available firmware for the T14s.
>>>>
>>>> We should stick with "memlat" if we run into a device in the
>>>> wild that doesn't support "MEMLAT"
>>>
>>> Ok. So the updated firmware supports both strings?
>>
>> Sry for the delay, was out sick. Yes the updated firmware supports both
>> strings.
> 
> No worries, hope you're feeling better.
> 
> I noticed that the firmware on the T14s indeed accepts both strings.
> 
> Johan