Re: [PATCH v4] clk: shmobile: div6: support selectable-input clocks

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On Fri, Aug 29, 2014 at 1:58 AM, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
[...]
> We could thus extend the DIV6 clocks with clock source selection using the
> following layout
>
> Bits     Name           Function
> -----------------------------------------------------------------------------
> 8        CKSTP    Clock Stop
> 7-6      EXSRC    Source Selection
> 5-0      DIV      Division Ratio
>
> The clocks property would be a list of one, two, three or four clock
> references, mapping to the 00, 01, 10 and 11 values of the EXSRC field. Empty
> references (just a 0 value) would be used to denote invalid values of the
> EXSRC field.
>
> A new compatible string would then be added for the VCLK clocks with the
> following layout
>
> Bits     Name           Function
> -----------------------------------------------------------------------------
> 14-12    EXSRC    Source Selection (VCLK[123] clocks)
> 8        CKSTP    Clock Stop
> 7-6      PDIV     PLL Division Ratio (VCLK3 clock)
> 5-0      DIV      Division Ratio

I think even a new compatible string would not be necessary, given
that all such clocks have more than four parents, which cannot be the
case for clocks with two EXSRC bits.

> The clocks property would be handled as for the common DIV6 clocks, and we
> would need to define a way to describe the valid values of the PDIV field. As
> far as I can see, the PDIV values are identical for all VCLK clocks when
> implemented (00 -> 1/1, 01 -> 1/2, 10 -> Reserved, 11 -> 1/4), so a single
> renesas,has-pdiv property should be enough.

Sounds reasonable to me.

I'll send a patch.

CU
Uli
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