linux-kernel - Re: [Patch 0/5] Support Autonomous Selection mode in cppc

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Message-ID: <da5d18c7-cf09-4956-ad9c-231b12cc0267@huawei.com>
Date: Sat, 22 Feb 2025 18:06:30 +0800
From: "zhenglifeng (A)" <zhenglifeng1@...wei.com>
To: Sumit Gupta <sumitg@...dia.com>, "Rafael J. Wysocki" <rafael@...nel.org>
CC: Viresh Kumar <viresh.kumar@...aro.org>, <lenb@...nel.org>,
	<robert.moore@...el.com>, <corbet@....net>, <linux-pm@...r.kernel.org>,
	<linux-acpi@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<acpica-devel@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<linux-tegra@...r.kernel.org>, <treding@...dia.com>, <jonathanh@...dia.com>,
	<sashal@...dia.com>, <vsethi@...dia.com>, <ksitaraman@...dia.com>,
	<sanjayc@...dia.com>, <bbasu@...dia.com>
Subject: Re: [Patch 0/5] Support Autonomous Selection mode in cppc_cpufreq

On 2025/2/21 21:14, Sumit Gupta wrote:
> 
> 
> On 19/02/25 00:53, Rafael J. Wysocki wrote:
>>
>> There seems to be some quite fundamental disagreement on how this
>> should be done, so I'm afraid I cannot do much about it ATM.
>>
>> Please agree on a common approach and come back to me when you are ready.
>>
>> Sending two concurrent patchsets under confusingly similar names again
>> and again isn't particularly helpful.
>>
>> Thanks!
> 
> Hi Rafael,
> 
> Thank you for looking into this.
> 
> Hi Lifeng,
> 
> As per the discussion, we can make the driver future extensible and
> also can optimize the register read/write access.
> 
> I gave some thought and below is my proposal.
> 
> 1) Pick 'Patch 1-7' from your patch series [1] which optimize API's
>    to read/write a cpc register.

'patch 1-7' in [1] doesn't conflicts with [2], so can be reviewed and
applied separately. I would follow this up in that series.

> 
> 2) Pick my patches in [2]:
>    - Patch 1-4: Keep all cpc registers together under acpi_cppc sysfs.
>                 Also, update existing API's to read/write regs in batch.
>    - Patch 5: Creates 'cppc_cpufreq_epp_driver' instance for booting
>      all CPU's in Auto mode and set registers with right values.
>      They can be updated after boot from sysfs to change hints to HW.
>      I can use the optimized API's from [1] where required in [2].
> 
> Let me know if you are okay with this proposal.
> I can also send an updated patch series with all the patches combined?

As mentioned above, 'patch 1-7' in [1] can be reviewed and applied
separately. No need to be combined with other patches.

About how to support auto selection mode in cppc_cpufreq, I think we need
to sort out usecases, scenarios, and requirements from both of us before we
disscus and agree on a design to implement. I am currently working on it
and will sent out my thoughts later.

Regards,
Lifeng

> 
> [1] https://lore.kernel.org/all/20250206131428.3261578-1-zhenglifeng1@huawei.com/
> [2] https://lore.kernel.org/lkml/20250211103737.447704-1-sumitg@nvidia.com/
> 
> Regards,
> Sumit Gupta
>