linux-kernel - Re: [PATCH] cpufreq: cpufreq-cpu0: Use a sane boot frequency when booting with a mismatched bootloader configuration

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Message-ID: <CAKohponU-WFnG8Gx6ba=k3eJmWV_0eWtpsy9kDP8yA2KrdoKtg@mail.gmail.com>
Date:	Sun, 17 Nov 2013 09:32:42 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Shawn Guo <shawn.guo@...aro.org>
Cc:	Nishanth Menon <nm@...com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Carlos Hernandez <ceh@...com>
Subject: Re: [PATCH] cpufreq: cpufreq-cpu0: Use a sane boot frequency when
 booting with a mismatched bootloader configuration

On 16 November 2013 19:14, Shawn Guo <shawn.guo@...aro.org> wrote:
> No, it's not a kernel bug.
>
> OPP is not a definition that belongs to kernel.  Instead, it's
> characteristics of hardware, and that's why we can naturally put the
> definition into device tree.  Bear it in mind that device tree is a
> hardware description and should be OS agnostic.  So it shouldn't be
> treated as part of Linux kernel in any case, even though the device
> tree source is currently maintained in kernel tree.
>
> Device tree is designed as a way for firmware/bootloader to describe
> hardware to kernel.  That said, device tree is more part of bootloader
> than kernel.  If bootloader runs at a frequency that does not match the
> OPP in device tree, the one should be fixed is either bootloader or
> device tree but never kernel.

I agree for all that..

> However, I agree we should at least have a check in cpufreq-cpu0 driver
> and fail out in case that a mismatch is detected.

But not here.. We aren't in a non-workable state here.. and so creating
panic isn't the right approach.

At max we can print an warning but then it doesn't lie in cpufreq-cpu0's
domain. It should be done in core if required..

Though for Shawn's information we have another thread in parallel for
this issue. You might like to check that too..

https://lkml.org/lkml/2013/11/15/503
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