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

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Date:   Thu, 7 Mar 2019 10:57:50 +0100
From:   Juri Lelli <juri.lelli@...il.com>
To:     Quentin Perret <quentin.perret@....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,

On 07/03/19 09:31, Quentin Perret wrote:
> 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.

If people think it's best to simply make this RO, I won't be against it.
Just pointed out a conversation we recently had. Guess we could also
make it RW again (properly) in the future if somebody complains.

Best,

- Juri