linux-kernel - Re: [PATCH v6 00/18] Consolidate and improve NVIDIA Tegra CPUIDLE driver(s)

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Message-ID: <9c25ea71-ebe9-d9c2-0dff-6b2752e27131@gmail.com>
Date:   Sat, 2 Nov 2019 00:30:35 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Peter De Schrijver <pdeschrijver@...dia.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 00/18] Consolidate and improve NVIDIA Tegra CPUIDLE
 driver(s)

01.11.2019 16:22, Dmitry Osipenko пишет:
> 01.11.2019 15:33, Peter De Schrijver пишет:
>> On Tue, Oct 29, 2019 at 03:47:56AM +0300, Dmitry Osipenko wrote:
>> ..
>>
>>>>>>> It would be useful to switch the power state terminology to the one used
>>>>>>> for later chips:
>>>>>>>
>>>>>>> LP0 becomes SC7
>>>>>>> LP1 becomes C1
>>>>>>> LP2 becomes CC7
>>>>>>>
>>>>>>> Meaning of these states is as follows
>>>>>>>
>>>>>>> C is a core state:
>>>>>>>
>>>>>>> C1 clock gating
>>>>>>> C2 not defined
>>>>>>> C3 not defined
>>>>>>> C4 not defined
>>>>>>> C5 not defined
>>>>>>> C6 not defined for ARM cores
>>>>>>> C7 power-gating
>>>>>>>
>>>>>>> CC is a CPU cluster C state:
>>>>>>>
>>>>>>> CC1 cluster clock gated
>>>>>>> CC2 not defined
>>>>>>> CC3 fmax@...n: not used prior to Tegra186
>>>>>>> CC4: cluster retention: no longer supported
>>>>>>> CC5: not defined
>>>>>>> CC6: cluster power gating
>>>>>>> CC7: cluster rail gating
>>>>>>>
>>>>>>> SC is a System C state:
>>>>>>>
>>>>>>> SC1: not defined
>>>>>>> SC2: not defined
>>>>>>> SC3: not defined
>>>>>>> SC4: not defined
>>>>>>> SC5: not defined
>>>>>>> SC6: not defined
>>>>>>> SC7: VDD_SOC off
>>>>>>
>>>>>> Hello Peter,
>>>>>>
>>>>>> But new "drivers/cpuidle/cpuidle-tegra.c" uses exactly that terminology,
>>>>>> please see "cpuidle: Refactor and move NVIDIA Tegra20 driver into
>>>>>> drivers/cpuidle/" and further patches. Am I missing something? Or do you
>>>>>> want the renaming to be a separate patch?
>>>>>>
>>>>>
>>>>> Or maybe you're suggesting to change the names everywhere and not only
>>>>> in the cpuidle driver? Please clarify :)
>>>>
>>>> At least some of the variable and function names still say lp2?
>>>
>>> The cpuidle driver uses LP2 terminology for everything that comes from
>>> the external arch / firmware includes. But it says CC6 for everything
>>> that is internal to the driver. So yes, there is a bit of new/old
>>> terminology mixing in the code.
>>>
>>> The arch code / PMC driver / TF firmware are all saying LP2. The LP2
>>> naming is also a part of the device-tree binding.
>>>
>>> It will be a lot of mess to rename the mach-tegra/pm.c code. I guess
>>> eventually it could be moved to drivers/soc/, so maybe it will be better
>>> to postpone the renaming until then?
>>
>> Or maybe add a comment somewhere indicating:
>>
>> LP2 = CC6
>> LP1 = C1
>> LP0 = SC7
>>
>> TF predates the new naming, so that may make some sense.
> 
> Today it should make more sense just to add an explicit comment to the
> cpuidle driver that clarifies the new naming (IMHO). I'll prepare v7
> with that change.
> 
> Maybe later on, once more code will be consolidated in
> drivers/soc/tegra/, it will become useful to duplicate the clarification
> there as well.
> 
> Please let me know if you disagree or think that something better could
> be done.

BTW, LP3 = C1.

I don't think that the new terminology has equivalent to LP1 (CPU
cluster power gating + DRAM in self-refresh).