linux-kernel - Re: [PATCH v1] arch_topology: Make cpu

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Message-ID: <20190307093116.slvugyeos46kl3et@queper01-lin>
Date:   Thu, 7 Mar 2019 09:31:19 +0000
From:   Quentin Perret <quentin.perret@....com>
To:     Juri Lelli <juri.lelli@...il.com>
Cc:     Lingutla Chandrasekhar <clingutla@...eaurora.org>,
        sudeep.holla@....com, dietmar.eggemann@....com,
        gregkh@...uxfoundation.org, will.deacon@....com,
        catalin.marinas@....com, morten.rasmussen@....com,
        linux-arm-kernel@...ts.infradead.org, jeremy.linton@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] arch_topology: Make cpu_capacity sysfs node as
 ready-only

Hi Juri,

On Thursday 07 Mar 2019 at 08:28:56 (+0100), Juri Lelli wrote:
> There are cases in which this needs to be RW, as recently discussed
> https://lore.kernel.org/lkml/20181123135807.GA14964@e107155-lin/

Yeah there's that problem when you can't fix your DT ... But I guess
this is a problem for _all_ values in the DT, not just capacities right ?
But these other values, I'd expected they just can't be fixed from
userspace most of the time, you just have to live with sub-optimal
values. So I don't find it unreasonable to do that for capacities too.

> IMHO, if the core_sibling assumption doesn't work in all cases, one
> should be looking into fixing it, rather than making this RO.

It's just that this thing keeps causing more harm than it helps IMO.
It's quite severely broken ATM, and it prevents us from assuming
'stable' capacity values in places were we'd like to do so (e.g. EAS).

And I'm not aware of a single platform where this is used. So, I'm
personally all for removing the write capability if we can.

Thanks,
Quentin