linux-kernel - Re: [PATCH V2 1/4] firmware: arm_scmi: Add perf_notify

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Date: Tue, 13 Feb 2024 11:10:22 +0530
From: Sibi Sankar <quic_sibis@...cinc.com>
To: Cristian Marussi <cristian.marussi@....com>,
        Sudeep Holla
	<sudeep.holla@....com>
CC: <viresh.kumar@...aro.org>, <morten.rasmussen@....com>, <rafael@...nel.org>,
        <dietmar.eggemann@....com>, <lukasz.luba@....com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <quic_mdtipton@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH V2 1/4] firmware: arm_scmi: Add perf_notify_support
 interface



On 2/12/24 18:14, Cristian Marussi wrote:
> On Wed, Jan 31, 2024 at 11:28:54AM +0000, Sudeep Holla wrote:
>> On Mon, Jan 29, 2024 at 05:33:42PM +0000, Cristian Marussi wrote:
> 
> Hi Sibi,
> 
>>> On Mon, Jan 29, 2024 at 03:50:20PM +0000, Cristian Marussi wrote:
>>>> On Wed, Jan 17, 2024 at 04:11:13PM +0530, Sibi Sankar wrote:
>>>>> Add a new perf_notify_support interface to the existing perf_ops to export
>>>>> info regarding limit/level change notification support.
>>>>>
>>>>
>>>> Hi Sibi,
>>>>
>>>> as I mentioned previously, in order not to add a needless stream of SCMI
>>>> Perf accessors I posted this:
>>>>
>>>> https://lore.kernel.org/linux-arm-kernel/20240129151002.1215333-1-cristian.marussi@arm.com/T/#u
>>>>
>>>> to expose all the Perf domains infos via the usual info_get(), similarly
>>>> to how other SCMI protocols do already.
>>>>
>>>> I think that reworking this series on that, you can certainly drop this patch and just
>>>> check the _notify booleans on the retrieved domain info.
>>>
>>> Sorry, but hold on with this change, I will probably post an updated version
>>> my patch above.
>>>
>>
>> As discussed in private, I would prefer to avoid exposing all the internals
>> to the users of SCMI perf. At the same time may we can do better if we can
>> check the availability of notification as part of notification enablement
>> from the SCMI driver, I need to think the details yet.
>>
> 
> as previously mentioned, after speaking with Sudeep, I posted a new
> series at [1], that aims to solve your problem with registering
> notifications and looking up reported Perf frequencies in a new way.
> 
> Using the changes at [1] you should be able to:
> 
> - register your notifier without caring to check if the notification
>    is supported, since the SCMI core will take care of checking that and
>    report an error if not supported, without sending any unneeded
>    attempted notification enable message  (so you can drop 1/4 in this
>    series)
> 
> - retrieve the pre-calculated OPPs frequencies from the new extended
>    Perf notifications reports no matter if the system if operating in
>    level_indexing_mode or not. (so you can drop 2/4 in this series)

Christian/Sudeep,

Thanks a lot for spending time on this and simplifying the series.

Will re-spin the series with your recommendations.

-Sibi

> 
> Thanks,
> Cristian
> 
> [1]: https://lore.kernel.org/linux-arm-kernel/20240212123233.1230090-1-cristian.marussi@arm.com/T/#ma68cefd753e34ba3e1f2d4392e978026a87e1bf8
>