[PATCH 0/4] Migrate PXA27x platforms to clock framework

Haojian Zhuang haojian.zhuang at gmail.com
Thu Jul 3 19:39:34 PDT 2014

On Fri, Jul 4, 2014 at 6:14 AM, Robert Jarzmik <robert.jarzmik at free.fr> wrote:
> Haojian Zhuang <haojian.zhuang at gmail.com> writes:
>>> Haojian, are you ok with that ? And BTW, does a combined kernel for PXA
>>> platforms even exists (mixing pxa3xx and pxa2xx for example) ?
>> It's acceptable to me that different silicons are queued in different stages.
>> I only request that it won't break the compiler building & bootup.
> OK.
>> But I think that the pxa clock driver may be shared among all PXA silicons
>> except for the clock table. What's your opinion?
> I don't think so because of the core clocks.
> These ones are specific to each pxa, and so their computation is :
>  - pxa25x plays with CCCR and specific L, M and N2 multiplication tables
>  - pxa27x plays with CCCR and specific L, M and N2 multiplication tables
>  - pxa3xx plays with ASCR, MEMCLKCFG, and AC97 div
> I don't see very well how a clock table could describe that. Do you have
> something specific in mind ?

As I remember, those registers bits are encoded. So we can define a clock mux
that connected to those fixed clock dividers. Then the clock gate is
the child of
the clock mux.

In DTS file, peripheral device node could specify a clock rate. In
peripheral device
driver, it could also change the clock rate by clk_set_rate().

>>>> Also (for my understanding) when you say that you plan to do
>>>> pxa25x and pxa3xx next, does that include pxa26x and pxa93x?
>>> I don't have the Technical Reference Manuals for these ones so the answer is
>>> no. And Google wasn't a great friend at providing them.
>> Converting them into new clock driver may not rely on the reference manual.
> Actually I went through the code and :
>  - pxa26x is only a superset of pxa25x with one more clock : pxa26x-gpio
>  - pxa93x is the same clock set as pxa3xx, right ?
> So if I convert pxa25x, pxa27x and pxa3xx I'll cover everything, right ?
>>>> I assume it does as they are apparently minor revisions of the
>>>> former, but it's not completely clear from your description.
>>> My description doesn't mention them, as I have no information about them, nor
>>> any hardware to test on.
>> We can request others to help testing in the mailing list.
> That's exactly what will enable pxa25x and pxa3xx. I have them converted in my
> tree, but I don't want to mix these patches in as I can't test them, and testing
> brings in bigger delays.

Delay shouldn't be the block issue.


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