Re: [PATCH v2 1/7] clk: Add a basic factor clock

[Maxime Ripard <maxime.ripard@free-electrons.com>]

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Hi Jim,

On Fri, Jul 24, 2015 at 08:50:17AM +0200, Maxime Ripard wrote:
> > Jim Quinlan submitted a similar patch. See here:
> > 
> > http://www.spinics.net/lists/linux-clk/msg00691.html
> 
> It looks very similar indeed.
> 
> > I nacked that patch because Stephen and I are trying to figure out how
> > the basic clock types should work going forward. Code reuse is good, but
> > they are not very maintainable.
> 
> What are the issues with maintaining them? The only drawback I'm
> seeing with introducing such a driver is that you can't really have a
> clock that is both a divider and a multiplier, but that can be solved
> by splitting it into two sub-clocks.
> 
> From a pure maintainance point of view, refusing it would mean that
> each and every platform would have to come up with its own
> implementation. For example, we do have clk-factors.c for sunxi that
> does just that, and implies some cooperation from each clock driver
> that have to provide some code to determine the various components of
> the output formula. This can prove to be very challenging (and bug
> prone) for clocks like the audio one we have where we have 1
> multiplier and 2 dividers that needs some adjusting.
> 
> Splitting it into sub-clocks for each of these components would allow
> to have less bugs, while keeping the whole thing very simple, and the
> implementation on the driver side very trivial.
> 
> Overall, the clk-factors code we have (client side) is approximately a
> thousand lines of code logic that could be replaced by (less) trivial
> probing code for such a driver.
> 
> > Since there are two potential users of this code, I should reconsider.
> 
> Like I said, eventually, I'd like to leverage that code a lot more
> than for the single clock alone, and I think it could benefit other
> platforms too (like Jim has proven).
> 
> > Can you two come up with a common implementation that works for both of
> > you?
> 
> Yes, sure. Jim, how do you want to go with this? Do you want to
> resubmit your patch on top of 4.2-rc something so that I could give it
> a try? Otherwise, I posted such a patch this week
> 
> https://lkml.kernel.org/r/1437235304-2208-1-git-send-email-maxime.ripard@free-electrons.com
> 
> Can you give it a try and your feedback?

Ping?

Maxime

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

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