linux-kernel - Re: [PATCH] pmdomain: arm: Fix debugfs node creation failure

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Message-ID: <48ac18f3-b831-91ab-4993-d82749052d8d@quicinc.com>
Date: Mon, 8 Jul 2024 15:37:04 +0530
From: Sibi Sankar <quic_sibis@...cinc.com>
To: Sudeep Holla <sudeep.holla@....com>
CC: <ulf.hansson@...aro.org>, <cristian.marussi@....com>,
        <linux-kernel@...r.kernel.org>, <arm-scmi@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        <quic_rgottimu@...cinc.com>, <quic_kshivnan@...cinc.com>,
        <johan@...nel.org>
Subject: Re: [PATCH] pmdomain: arm: Fix debugfs node creation failure



On 7/5/24 18:34, Sudeep Holla wrote:
> On Fri, Jul 05, 2024 at 09:16:29AM +0530, Sibi Sankar wrote:
>>
>> On 7/4/24 16:02, Sudeep Holla wrote:
>>>
>>> If there are 2 perf domains for a device or group of devices, there must
>>> be something unique about each of these domains. Why can't the firmware
>>> specify the uniqueness or the difference via the name?
>>>
>>> The example above seems firmware is being just lazy to update it. Also
>>> for the user/developer/debugger, the unique name might be more useful
>>> than just this number.
>>>
>>> So please use the name(we must now have extended name if 16bytes are less)
>>> to provide unique names. Please stop working around such silly firmware
>>> bugs like this, it just makes using debugfs for anything useful harder.
>>
>> This is just meant to address firmware that are already out in the wild.
>> That being said I don't necessarily agree with the patch either since
>> it's penalizing firmware that actually uses a proper name by appending
>> something inherently less useful to it. Since, the using of an unique
>> domain name isn't required by the spec, the need for it goes under the radar
>> for vendors. Mandating it might be the right thing to do since
>> the kernel seems inherently expect that.
>>
> 
> Well I would love if spec authors can agree and mandate this. But this is
> one of those things I can't argue as I don't necessarily agree with the
> argument. There are 2 distinct/unique domains but firmware authors ran out
> of unique names for them or just can't be bothered to care about it.
> 
> They can't run out of characters as well in above examples, firmware can
> add some useless domain ID in the name if they can't be bothered or creative.
> 
> So I must admit I can't be bothered as well with that honestly.

Okay, I guess the conclusion is that if the firmware vendors
don't care enough to provide unique names, they get to live
without those debugfs nodes.

Do we really want to register/expose scmi perf power-domains used by
the CPU nodes? Given that scmi-cpufreq doesn't consume these power
domains and can be voted upon by another consumer, wouldn't this cause
a disconnect?

-Sibi

> --
> Regards,
> Sudeep