linux-kernel - Re: [PATCH 3/5] ARM: berlin/dt: add cpupll and syspll support to BG2Q

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Message-ID: <20140321145403.GC6443@piout.net>
Date:	Fri, 21 Mar 2014 15:54:03 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Cc:	Mike Turquette <mturquette@...aro.org>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>
Subject: Re: [PATCH 3/5] ARM: berlin/dt: add cpupll and syspll support to BG2Q

On 21/03/2014 at 13:29:31 +0100, Sebastian Hesselbarth wrote :
> >>Hmm, you probably know better than me, but if cpuclk == cpupll
> >>is always true we don't need another clk layer here. If you
> >>can scale down cpuclk from cpupll and we just have no driver
> >>for it, I am fine with it.
> >>
> >
> >You can actually switch CPU clk from CPU pll to smclk. I'm not sure this
> >is completely useful yet though, probably for suspend ?
> 
> Then it should be clk mux instead?
> 
> >Also, while I'm not sure this is a good reason, other clocks are derived
> >from CPU pll and have another divider.
> 
> I have no strong opinion, but a fixed-factor-clock with 1:1 just to
> rename cpupll to cpuclk seems a bit wasty ;)
> 
> If there is a mux, we should add it now - no matter if we are ever
> going to make any use of it. For the derived clocks we should be
> careful if they actually depend on cpuclk or always cpupll.
> 
> If your (current) knowledge of the berlin clock trees is almost as
> bad as mine, we can also ignore cpuclk mux if you prefer.
> 

Yeah, fact is I know there is a mux but I don't know yet how to get/set
its state so I will ignore it until we have more info.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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