linux-kernel - Re: [PATCH 7/8] cpufreq: Remove support for hardware P-state chips from powernow-k8

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Date:	Mon, 20 Aug 2012 22:49:16 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Andre Przywara <andre.przywara@....com>
Cc:	cpufreq@...r.kernel.org, Matthew Garrett <mjg@...hat.com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Thomas Renninger <trenn@...e.de>, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/8] cpufreq: Remove support for hardware P-state chips from powernow-k8

On Monday, August 20, 2012, Andre Przywara wrote:
> On 08/05/2012 11:33 PM, Rafael J. Wysocki wrote:
> > On Thursday, July 26, 2012, Andre Przywara wrote:
> >> From: Matthew Garrett <mjg@...hat.com>
> >>
> >> These chips are now supported by acpi-cpufreq, so we can delete all the
> >> code handling them.
> >>
> >> Signed-off-by: Matthew Garrett <mjg@...hat.com>
> >> Signed-off-by: Andre Przywara <andre.przywara@....com>
> >
> > Would it be very wrong/confusing to keep that support in the powernow-k8
> > driver for the time being, perhaps making it print a message that the ACPI
> > driver is recommended for those chips?
> 
> Why would you like to do this? Are you concerned about regressions?

Yes.  Suppose you have a system configured to use the powernow-k8 driver
right now and you find that it stopped working due to a kernel update.
You would be quite upset I suppose.

> Or do you just want to avoid the introduction of the doomed "cpb" feature 
> in acpi-cpufreq?
> 
> I am not sure if keeping support in powernow-k8 would just make people 
> use it still in the future. At least if it would just load easily as before.
> One idea could be to keep the code around, but only load on family 10h 
> if a force_fam10h or so command line option is provided. But again this 
> could just push distributions to provide this option to avoid the 
> transition.

We don't force transitions like that, mind you.

> One of my motivations was to keep only _one_ driver around, the code 
> removal of the fam10h support from powernow-k8 supports this.
> 
> If you insist, I can keep the code in powernow-k8, but it probably 
> wouldn't receive any support anymore and would increase confusion on the 
> user side.

I'm not afraid of that.  And as I said, you can just add info messages to
powernow-k8 saying that the feature is deprecated and will be removed in the
future and _then_ you actually _can_ remove it in the future (say, 2-3 major
kernel releasew from now).

Thanks,
Rafael
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