Re: [PATCH v3] clk: add si5351 i2c common clock driver

[Michal Bachraty <michal.bachraty-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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Hi Sebastian,

I posted patch for gap-less tuning. It is based on v5 of your driver.  This
patch was tested for tuning with 1ppm clock step.

Best,
Michal.


On Mon, Mar 25, 2013 at 12:54 PM, Sebastian Hesselbarth <
sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> On Wed, Mar 20, 2013 at 5:48 PM, Daniel Mack <zonque-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > On 20.03.2013 14:55, michal.bachraty-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote:
> >> Thanks for writing this driver! I have tested your si5351 clock
> >> driver and his tuning capabilities. It works well, it generates
> >> proper clock frequency, but when new frequency is generated, little
> >> clock gap (1ms) is generated. Si5351 datasheet and WP claims, clock
> >> tuning can be without gaps -
> >>
> http://www.silabs.com/Support%20Documents/TechnicalDocs/Si5350-51-Frequency-Shifting-WP.pdf
> >>
> >> I made some tests with Si5351A chip and I found that when tuning touch
> >> only Multisynth registers, it can tune without gaps. There is no need
> >> for soft PLL reset. I found also, accessing Multisynth registers is not
> >> atomic, so there can be another frequency at output, while not all
> >> registers are written. Writing only to one register seems to be atomic.
>
> Michael,
>
> if you don't configure the clock output to modify the pll, changing output
> frequency will not alter pll config and there will be no reset of pll.
>
> > Yeah, but limiting possible changes to the PLLs to one single register
> > also means that you cannot offer to generate all the frequencies any
> > more. What could probably be done is refine the algorithm so that it
> > stays 'as close as possible' to the former values, but I'm not sure how
> > much work that implies.
> >
> > Can you provide a patch against Sebastian's v3 to do that? Then it can
> > be cleanly applied on top of the driver later.
>
> Ack. Feel free to post a patch on top of v4 now.
>
> Sebastian
>

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