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

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Message-ID: <064274c4-3783-c59e-e293-dd53a8595d8e@quicinc.com>
Date: Fri, 5 Jul 2024 09:16:29 +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 7/4/24 16:02, Sudeep Holla wrote:
> On Wed, Jul 03, 2024 at 04:37:41PM +0530, Sibi Sankar wrote:
>> The domain attributes returned by the perf protocol can end up
>> reporting identical names across domains, resulting in debugfs
>> node creation failure. Fix this duplication by appending the
>> domain-id to the domain name.

Hey Sudeep,

Thanks for taking time to review the patch :)

>>
>> Logs:
>> debugfs: Directory 'NCC' with parent 'pm_genpd' already present!
>> debugfs: Directory 'NCC' with parent 'pm_genpd' already present!
>>
> 
> 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.

-Sibi

> 
> --
> Regards,
> Sudeep