Re: ACPI PCC probe failed.

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Hi Rafael,

On 4 February 2015 at 20:28, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> On Wednesday, February 04, 2015 06:38:39 PM Ashwin Chaugule wrote:
>> On 4 February 2015 at 18:04, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
>> > On Wednesday, February 04, 2015 05:06:26 PM Ashwin Chaugule wrote:
>> >> > I have one more concern about this driver.  Namely, what benefit is there to
>> >> > people like Cristian from it at all?
>> >>
>> >> Its of use only if they have a PCC client (MPST, CPPC, RAS) driver.
>> >> Looks like PCC was explicitly enabled in this kernel.
>> >>
>> >> config PCC
>> >> bool "Platform Communication Channel Driver"
>> >> depends on ACPI
>> >
>> > Can we make it depend on the clients instead and be set automatically
>> > when at least one of the clients is enabled?
>> >
>> > Otherwise distros will have a problem with deciding whether or not they
>> > should enable this driver and most of them will end up enabling it.
>>
>> I see your point, but I'm not aware of any upstreamed client as of
>> yet. There might be folks using this driver internally though with
>> other clients. In such a case, is there a way to keep PCC disabled
>> until a client (e.g. CPPC) is upstreamed?
>
> Make it depend on EXPERT or something like that until the first client is
> added and then make it depend on that client. :-)

Doesn't sound too bad. Hope that doesn't end up enabling unintended
options in the kernel which aren't exposed in kconfig.
FWIW, I think its better to make it depend on CPPC as part of the PCC
cleanup patch that I have going in the CPPC patchset.

>
>> Alternately, is it that bad to keep it the way it is, given that the
>> driver wont do anything unless PCCT is detected in firmware and a PCC
>> client explicitly uses its API?
>
> Well, is it really useful this way?

Not really, but not particularly harmful either. :) Besides, it seems
like for the sake of genericness, distros enable several options that
are irrelevant to a platform. In this case, PCC would be harmlessly
enabled only until CPPC makes its way upstream (which is actively
being worked on anyway).

Cheers,
Ashwin.
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