From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Doug Anderson <dianders@chromium.org>, Lukasz Luba <lukasz.luba@arm.com>
Cc: Matthias Kaehlcke <mka@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
amit daniel kachhap <amit.kachhap@gmail.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Amit Kucheria <amitk@kernel.org>, Zhang Rui <rui.zhang@intel.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Pierre.Gondois@arm.com, Stephen Boyd <swboyd@chromium.org>,
Rajendra Nayak <rnayak@codeaurora.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
jorcrous@amazon.com, Rob Clark <robdclark@chromium.org>,
Manaf Meethalavalappu Pallikunhi <quic_manafm@quicinc.com>
Subject: Re: [PATCH 1/2] thermal: cooling: Check Energy Model type in cpufreq_cooling and devfreq_cooling
Date: Thu, 17 Feb 2022 19:27:36 +0100 [thread overview]
Message-ID: <3651bf48-eb0f-1835-3c5e-1dbdc2730fb4@linaro.org> (raw)
In-Reply-To: <CAD=FV=WMaMP84YLZxBZbj4DJSgcDLVkSHf4QdDwtFfp8UbyE7A@mail.gmail.com>
Adding Manaf (QCom) in the loop
On 17/02/2022 17:37, Doug Anderson wrote:
> Hi,
>
> On Thu, Feb 17, 2022 at 2:47 AM Lukasz Luba <lukasz.luba@arm.com> wrote:
>>
>> Hi Daniel,
>>
>> On 2/17/22 10:10 AM, Daniel Lezcano wrote:
>>> On 16/02/2022 18:33, Doug Anderson wrote:
>>>> Hi,
>>>>
>>>> On Wed, Feb 16, 2022 at 7:35 AM Lukasz Luba <lukasz.luba@arm.com> wrote:
>>>>>
>>>>> Hi Matthias,
>>>>>
>>>>> On 2/9/22 10:17 PM, Matthias Kaehlcke wrote:
>>>>>> On Wed, Feb 09, 2022 at 11:16:36AM +0000, Lukasz Luba wrote:
>>>>>>>
>>>>>>>
>>>>>>> On 2/8/22 5:25 PM, Matthias Kaehlcke wrote:
>>>>>>>> On Tue, Feb 08, 2022 at 09:32:28AM +0000, Lukasz Luba wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>
>>>>> [snip]
>>>>>
>>>>>>>>> Could you point me to those devices please?
>>>>>>>>
>>>>>>>> arch/arm64/boot/dts/qcom/sc7180-trogdor-*
>>>>>>>>
>>>>>>>> Though as per above they shouldn't be impacted by your change,
>>>>>>>> since the
>>>>>>>> CPUs always pretend to use milli-Watts.
>>>>>>>>
>>>>>>>> [skipped some questions/answers since sc7180 isn't actually
>>>>>>>> impacted by
>>>>>>>> the change]
>>>>>>>
>>>>>>> Thank you Matthias. I will investigate your setup to get better
>>>>>>> understanding.
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>
>>>>> I've checked those DT files and related code.
>>>>> As you already said, this patch is safe for them.
>>>>> So we can apply it IMO.
>>>>>
>>>>>
>>>>> -------------Off-topic------------------
>>>>> Not in $subject comments:
>>>>>
>>>>> AFAICS based on two files which define thermal zones:
>>>>> sc7180-trogdor-homestar.dtsi
>>>>> sc7180-trogdor-coachz.dtsi
>>>>>
>>>>> only the 'big' cores are used as cooling devices in the
>>>>> 'skin_temp_thermal' - the CPU6 and CPU7.
>>>>>
>>>>> I assume you don't want to model at all the power usage
>>>>> from the Little cluster (which is quite big: 6 CPUs), do you?
>>>>> I can see that the Little CPUs have small dyn-power-coeff
>>>>> ~30% of the big and lower max freq, but still might be worth
>>>>> to add them to IPA. You might give them more 'weight', to
>>>>> make sure they receive more power during power split.
>>>>>
>>>>> You also don't have GPU cooling device in that thermal zone.
>>>>> Based on my experience if your GPU is a power hungry one,
>>>>> e.g. 2-4Watts, you might get better results when you model
>>>>> this 'hot' device (which impacts your temp sensor reported value).
>>>>
>>>> I think the two boards you point at (homestar and coachz) are just the
>>>> two that override the default defined in the SoC dtsi file. If you
>>>> look in sc7180.dtsi you'll see 'gpuss1-thermal' which has a cooling
>>>> map. You can also see the cooling maps for the littles.
>>>>
>>>> I guess we don't have a `dynamic-power-coefficient` for the GPU,
>>>> though? Seems like we should, but I haven't dug through all the code
>>>> here...
>>>
>>> The dynamic-power-coefficient is available for OPPs which includes
>>> CPUfreq and devfreq. As the GPU is managed by devfreq, setting the
>>> dynamic-power-coefficient makes the energy model available for it.
>>>
>>> However, the OPPs must define the frequency and the voltage. That is the
>>> case for most platforms except on QCom platform.
>>>
>>> That may not be specified as it uses a frequency index and the hardware
>>> does the voltage change in our back. The QCom cpufreq backend get the
>>> voltage table from a register (or whatever) and completes the voltage
>>> values for the OPPs, thus adding the information which is missing in the
>>> device tree. The energy model can then initializes itself and allows the
>>> usage of the Energy Aware Scheduler.
>>>
>>> However this piece of code is missing for the GPU part.
>>>
>>
>> Thank you for joining the discussion. I don't know about that Qcom
>> GPU voltage information is missing.
>>
>> If the voltage is not available (only the frequencies), there is
>> another way. There is an 'advanced' EM which uses registration function:
>> em_dev_register_perf_domain(). It uses a local driver callback to get
>> power for each found frequency. It has benefit because there is no
>> restriction to 'fit' into the math formula, instead just avg power
>> values can be feed into EM. It's called 'advanced' EM [1].
>
> It seems like there _should_ be a way to get the voltage out for GPU
> operating points, like is done with cpufreq in
> qcom_cpufreq_hw_read_lut(), but it might need someone with Qualcomm
> documentation to help with it. Maybe Rajendra would be able to help?
> Adding Jordon and Rob to this conversation in case they're aware of
> anything.
>
> As you said, we could just list a power for each frequency, though.
>
> I'm actually not sure which one would be more accurate across a range
> of devices with different "corners": specifying a dynamic power
> coefficient used for all "corners" and then using the actual voltage
> and doing the math, or specifying a power number for each frequency
> and ignoring the actual voltage used. In any case we're trying to get
> ballpark numbers and not every device will be exactly the same, so
> probably it doesn't matter that much.
>
>
>> Now we hit (again) the DT & EM issue (it's an old one, IIRC Morten
>> was proposing from ~2014 this upstream, but EAS wasn't merged back
>> then):
>> where to store these power-freq values, which are then used by the
>> callback. We have the 'dynamic-power-coefficient' in DT, but
>> it has limitations. It would be good to have this simple array
>> attached to the GPU/CPU node. IMHO it meet the requirement of DT,
>> it describes the HW (it would have HZ and Watts values).
>>
>> Doug, Matthias could you have a look at that function and its
>> usage, please [1]?
>> If you guys would support me in this, I would start, with an RFC
>> proposal, a discussion on LKML.
>>
>> [1]
>> https://elixir.bootlin.com/linux/v5.17-rc4/source/Documentation/power/energy-model.rst#L87
>
> Matthias: I think you've spent more time on the thermal stuff than me
> so I'll assume you'll follow-up here. If not then please yell!
>
> Ideally, though, someone from Qualcomm would jump in an own this.
> Basically it allows more intelligently throttling the GPU and CPU
> together in tandem instead of treating them separately IIUC, right?
>
> -Doug
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next prev parent reply other threads:[~2022-02-17 18:28 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 7:30 [PATCH 0/2] Ignore Energy Model with abstract scale in IPA and DTPM Lukasz Luba
2022-02-07 7:30 ` [PATCH 1/2] thermal: cooling: Check Energy Model type in cpufreq_cooling and devfreq_cooling Lukasz Luba
2022-02-08 0:50 ` Matthias Kaehlcke
2022-02-08 9:32 ` Lukasz Luba
2022-02-08 17:25 ` Matthias Kaehlcke
2022-02-09 11:16 ` Lukasz Luba
2022-02-09 22:17 ` Matthias Kaehlcke
2022-02-16 15:35 ` Lukasz Luba
2022-02-16 17:33 ` Doug Anderson
2022-02-16 22:13 ` Matthias Kaehlcke
2022-02-16 22:43 ` Lukasz Luba
2022-02-17 0:26 ` Matthias Kaehlcke
2022-02-17 10:15 ` Daniel Lezcano
2022-02-17 9:59 ` Daniel Lezcano
2022-02-17 10:10 ` Daniel Lezcano
2022-02-17 10:47 ` Lukasz Luba
2022-02-17 11:28 ` Daniel Lezcano
2022-02-17 12:11 ` Lukasz Luba
2022-02-17 12:33 ` Daniel Lezcano
2022-02-17 12:37 ` Lukasz Luba
2022-02-17 16:46 ` Matthias Kaehlcke
2022-02-17 16:37 ` Doug Anderson
2022-02-17 17:14 ` Matthias Kaehlcke
2022-02-17 18:05 ` Lukasz Luba
2022-02-17 18:27 ` Daniel Lezcano [this message]
2022-02-16 17:21 ` Doug Anderson
2022-02-16 23:28 ` Lukasz Luba
2022-02-17 16:50 ` Doug Anderson
2022-02-17 17:58 ` Lukasz Luba
2022-02-17 18:18 ` Lukasz Luba
2022-02-22 17:05 ` Lukasz Luba
2022-02-22 18:12 ` Daniel Lezcano
2022-02-22 18:31 ` Lukasz Luba
2022-02-22 22:10 ` Daniel Lezcano
2022-02-23 9:10 ` Lukasz Luba
2022-02-07 7:30 ` [PATCH 2/2] powercap: DTPM: Check Energy Model type for power values scale Lukasz Luba
2022-02-07 10:41 ` [PATCH 0/2] Ignore Energy Model with abstract scale in IPA and DTPM Daniel Lezcano
2022-02-07 11:44 ` Lukasz Luba
2022-02-08 7:39 ` Daniel Lezcano
2022-02-08 9:47 ` Lukasz Luba
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