Messages in this thread | | | Date | Fri, 08 Mar 2013 14:30:27 +0100 | From | Daniel Mack <> | Subject | Re: Question about fixed-clock |
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On 08.03.2013 03:15, Mark Brown wrote: > On Thu, Mar 07, 2013 at 11:31:59PM +0100, Daniel Mack wrote: >> On 07.03.2013 19:42, Afzal Mohammed wrote: > >>> I feel that for a platform having it's clock tree in DT, of_clk_init >>> would take care of it, but if clock tree data is not in DT, clock >>> tree would have to be extended in a non-DT way. > >> Hmm, I don't follow. So for generic OMAP board in general which does >> *not* have its SoC clocks in DT, the question is who's in charge of >> registering out-of-SoC fixed clocks that are defined in DT. > >> Note that the clock I'm dealing with here is _outside_ of the SoC, and I >> just need to have it in DT, so it can feed another clock chip's input pin. > >> Grep'ing through arch/arm, it seems that the imx arch does the same >> thing my patch does, but I could also imagine that it should be done >> somewhere from the DT core. I copied Grant, Rob and Mark for more comments. > > Wouldn't this just be set up by the DT in the same way that other > off-SoC hardware is?
Well, I thought so too. To repeat, in my DT, I have:
ref25: ref25M { compatible = "fixed-clock"; #clock-cells = <0>; clock-frequency = <25000000>; };
to represent an osciallator on the board. I need to specify it here so I can pass a reference to another chip:
si5351a: clock-generator@60 { compatible = "silabs,si5351a"; clocks = <&ref25>; };
I would have expected that "fixed-clock" is matched by a driver lurking around for DT boards, just like what the "fixed-regulator" driver does for instance. But the clock device isn't initialized unless board code explicitly calls of_clk_init() with a table mentioning "fixed-clock", as in my patch.
I don't know the clock framework well enough, but it seems that either all DT boards are supposed to do the same in their generic bits (which sounds like a lot of code duplication), or the fixed-clock driver should behave like any other driver wrt its probing from DT. I'm open to suggestions :)
Daniel
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