linux-kernel - Re: [PATCH 2/2] clk: uniphier: add clock data for cpufreq

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Date:   Wed, 23 Nov 2016 18:10:56 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-clk <linux-clk@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2] clk: uniphier: add clock data for cpufreq

On 11/24, Masahiro Yamada wrote:
> Hi Stephen,
> 
> 
> 2016-11-24 9:05 GMT+09:00 Stephen Boyd <sboyd@...eaurora.org>:
> 
> >> +#if 1
> >> +     /*
> >> +      * TODO:
> >> +      * The return type of .round_rate() is "long", which is 32 bit wide on
> >> +      * 32 bit systems.  Clock rate greater than LONG_MAX (~ 2.15 GHz) is
> >> +      * treated as an error.  Needs a workaround until the problem is fixed.
> >> +      */
> >
> > Just curious is the problem internal to the clk framework because
> > of the clk_ops::round_rate design? Or does the consumer, cpufreq
> > in this case, have to deal with rates that are larger than
> > unsigned long on a 32 bit system? If it's just a clk_ops problem
> > and we need to support rates up to 32 bits wide (~ 4.3 GHz) on
> > the system then the driver could be changed to use
> > .determine_rate() ops and that would allow us to use all the bits
> > of unsigned long to figure out rates.
> >
> > If the problem is rates even larger than unsigned long on 32 bit
> > systems, then at the least I'd like to see some sort of plan to
> > fix that in the framework before merging code. Hopefully it can
> > be done gradually, but as I start looking at it it seems more and
> > more complicated to support this so this will be a long term
> > project.
> >
> > We can discuss the clk API changes needed as well if those are
> > required, but that is another issue that requires changes in
> > other places outside of clk drivers.
> >
> 
> I understand your point, but core frame-work changes
> need more careful review than clk data changes in low-level drivers.
> It is too late to be included in v4.10.
> 
> If I drop 32bit SoC things, and send v2 only for 64bit SoCs,
> is that acceptable for 4.10-rc1?

Sure. That sounds fine for now. I'll reply to your other thread
with a plan of attack on how to do the framework changes. I think
we need to do those regardless of the outcome of your
investigation.

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