linux-kernel - Re: [PATCH] cpufreq: Processor Clocking Control interface driver

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Message-ID: <20091215183331.GA5560@comet.dominikbrodowski.net>
Date:	Tue, 15 Dec 2009 19:33:31 +0100
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	"Chumbalkar, Nagananda" <Nagananda.Chumbalkar@...com>
Cc:	"davej@...hat.com" <davej@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"mjg@...hat.com" <mjg@...hat.com>, "trenn@...e.de" <trenn@...e.de>,
	"lenb@...nel.org" <lenb@...nel.org>
Subject: Re: [PATCH] cpufreq: Processor Clocking Control interface driver

Hey,

On Tue, Dec 15, 2009 at 06:08:08PM +0000, Chumbalkar, Nagananda wrote:
> Hi, I have addressed your concerns below: 

Thanks!

> >If this is _really_ necessary... Doesn't the driver version 
> >relate to some
> >Linux kernel version anyway?
> >
> 
> If distros backport this driver to different kernel versions, it will be
> easy to keep track of which driver version is in the distro.

Well, IMVHO it's ugly, but if Linux ACPI and cpufreq folks are fine with
it, so be it.

> Yes, it works fine. Both "ondemand" and "conservative" sanitize the
> latency value, and set it to a default value which is good.

OK. Any way to fix the spec for the next revision, though?

> >> +	if (target_freq <= 
> >(ioread32(&pcch_hdr->minimum_frequency) * 1000)) {
> >> +		target_freq = 
> >ioread32(&pcch_hdr->minimum_frequency) * 1000;
> >> +		dprintk("target: target_freq for cpu %d was 
> >below limit, "
> >> +			"converted it to %d\n", cpu, target_freq);
> >> +	}
> >
> >why not do this in the _verify() step? Does pcch_hdr->minimum_frequency
> >even change "on the fly"?
> 
> pcch_hdr->minimum_frequency does not change "on the fly". Also, there is no
> need for those IO accesses:

target_freq cannot be below policy->min or above policy->max. If it were,
the whole cpufreq subsystem is broken. So there's no need for these checks,
AFAICS.

Best,
	Dominik
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