linux-kernel - Re: [PATCH 1/2] acpi: cppc: add cpufreq device

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Date:   Thu, 10 Dec 2020 17:55:56 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Mian Yousaf Kaukab <ykaukab@...e.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Mian Yousaf Kaukab <yousaf.kaukab@...e.com>,
        Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ionela Voinescu <ionela.voinescu@....com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Petr Cervinka <pcervinka@...e.com>
Subject: Re: [PATCH 1/2] acpi: cppc: add cpufreq device

On Thursday, December 10, 2020 4:04:40 PM CET Mian Yousaf Kaukab wrote:
> On Thu, Dec 10, 2020 at 03:32:09PM +0100, Rafael J. Wysocki wrote:
> > On Thu, Dec 10, 2020 at 3:23 PM Mian Yousaf Kaukab
> > <yousaf.kaukab@...e.com> wrote:
> > >
> > > Convert cppc-cpufreq driver to a platform driver (done in a separate patch)
> > > and add cppc-cpufreq device when acpi_cppc_processor_probe() succeeds.
> > 
> > Honestly, I prefer to drop 28f06f770454 (along with its follower)
> > instead of making this change.
> > 
> Even if we revert 28f06f770454 there is still one more small issue that these
> patches fix. Currently, ACPI_PROCESSOR_DEVICE_HID is used to load cppc-cpufreq
> module. In case when CPPC is disabled, some cycles will be wasted in loading
> cppc-cpufreq module. The module will return error from the init call though
> so no memory is wasted.
> 
> After converting to platform-driver, cppc-cpufreq module will only be loaded
> when the platform-device is available.

Even so, that issue is low-impact AFAICS and may be addressed later and I'd
rather not let known breakage go into the mainline.

I'm going to do drop the problematic commit now and please work with Ionela
to produce a clean series of patches in the right order to avoid introducing
issues between them.

If that is done timely enough, it may still be possible to push those patches
for 5.11-rc1.

Thanks!