linux-kernel - Re: [PATCH v5 2/4] dt-bindings: cpufreq: apple,soc-cpufreq: Add binding for Apple SoC cpufreq

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Date:   Tue, 29 Nov 2022 15:34:26 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Hector Martin <marcan@...can.st>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Mark Kettenis <mark.kettenis@...all.nl>, asahi@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v5 2/4] dt-bindings: cpufreq: apple,soc-cpufreq: Add
 binding for Apple SoC cpufreq

On 29/11/2022 15:00, Hector Martin wrote:
> On 29/11/2022 20.36, Ulf Hansson wrote:
>> On Mon, 28 Nov 2022 at 15:29, Hector Martin <marcan@...can.st> wrote:
>>> +examples:
>>> +  - |
>>> +    // This example shows a single CPU per domain and 2 domains,
>>> +    // with two p-states per domain.
>>> +    // Shipping hardware has 2-4 CPUs per domain and 2-6 domains.
>>> +    cpus {
>>> +      #address-cells = <2>;
>>> +      #size-cells = <0>;
>>> +
>>> +      cpu@0 {
>>> +        compatible = "apple,icestorm";
>>> +        device_type = "cpu";
>>> +        reg = <0x0 0x0>;
>>> +        operating-points-v2 = <&ecluster_opp>;
>>
>> To me, it looks like the operating-points-v2 phandle better belongs in
>> the performance-domains provider node. I mean, isn't the OPPs really a
>> description of the performance-domain provider?
>>
>> That said, I suggest we try to extend the generic performance-domain
>> binding [1] with an "operating-points-v2". In that way, we should
>> instead be able to reference it from this binding.
>>
>> In fact, that would be very similar to what already exists for the
>> generic power-domain binding [2]. I think it would be rather nice to
>> follow a similar pattern for the performance-domain binding.
> 
> While I agree with the technical rationale and the proposed approach
> being better in principle...
> 
> We're at v5 of bikeshedding this trivial driver's DT binding, and the
> comment could've been made at v3. To quote IRC just now:
> 
>> this way the machines will be obsolete before things are fully upstreamed
> 
> I think it's long overdue for the kernel community to take a deep look
> at itself and its development and review process, because it is quite
> honestly insane how pathologically inefficient it is compared to,
> basically, every other large and healthy open source project of similar
> or even greater impact and scope.
> 
> Cc Linus, because this is for your Mac and I assume you care. We're at
> v5 here for this silly driver. Meanwhile, rmk recently threw the towel
> on upstreaming macsmc for us. We're trying, and I'll keep trying because
> I actually get paid (by very generous donors) to do this, but if I
> weren't I'd have given up a long time ago. And while I won't give up, I
> can't deny this situation affects my morale and willingness to keep
> pushing on upstreaming on a regular basis.
> 
> Meanwhile, OpenBSD has been *shipping* full M1 support for a while now
> in official release images (and since Linux is the source of truth for
> DT bindings, every time we re-bikeshed it we break their users because
> they, quite reasonably, aren't interested in waiting for us Linux
> slowpokes to figure it out first).
> 
> Please, let's introspect about this for a moment. Something is deeply
> broken if people with 25+ years being an arch maintainer can't get a

If arch maintainer sends patches which does not build (make
dt_binding_check), then what do you exactly expect? Accept them just
because it is 25+ years of experience or a maintainer? So we have
difference processes - for beginners code should compile. For
experienced people, it does not have to build because otherwise they
will get discouraged?

> 700-line mfd driver upstreamed before giving up. I don't know how we
> expect to ever get a Rust GPU driver merged if it takes 6+ versions to
> upstream the world's easiest cpufreq hardware.

While I understand your point about bikeschedding, but I think your
previous bindings got pretty nice and fast reviews, so using examples of
non-building case is poor choice.

Best regards,
Krzysztof