[PATCH 2/5] clk: bcm2835: enable management of PCM clock

Martin Sperl kernel at martin.sperl.org
Sun Jan 10 02:55:48 PST 2016

> On 10.01.2016, at 10:30, Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> Hi Arnd,
> On Sat, Jan 9, 2016 at 9:56 PM, Arnd Bergmann <arnd at arndb.de> wrote:
>> On Saturday 09 January 2016 09:25:54 kernel at martin.sperl.org wrote:
>>> --- a/include/dt-bindings/clock/bcm2835.h
>>> +++ b/include/dt-bindings/clock/bcm2835.h
>>> @@ -44,5 +44,6 @@
>>> #define BCM2835_CLOCK_EMMC             28
>>> #define BCM2835_CLOCK_PERI_IMAGE       29
>>> #define BCM2835_CLOCK_PWM              30
>>> +#define BCM2835_CLOCK_PCM              31
>>> -#define BCM2835_CLOCK_COUNT            31
>>> +#define BCM2835_CLOCK_COUNT            32
>> The last line contains an incompatible change, please don't do that.
>> If you have to add another clock, do that after the BCM2835_CLOCK_COUNT
>> definition to avoid changing dts files that use that number.
> While I agree this changes dts files (in an unexpected way?), not updating
> BCM2835_CLOCK_COUNT makes it definition useless. Which teaches that
> having such definitions in DT headers is not a good idea in the first place...
> Hence it can better be replaced (it seems to be unused in dts files, but you
> can keep the definition to be 100% sure) by an ARRAY_SIZE() in the C driver.
> This requires changing the driver to e.g. initialize clks[] in
> bcm2835_clk_probe() based on a table instead of explicit code.

That is a more general issue with the clock driver (and there
have been already some discussions around this when implementing
the PWM clock.

So if someone with a better idea how to keep those dt-binding includes
synchronized with the definitions used by the code step forward and
propose a better solution how to get that implemented?

I guess there will be a few more occurrences of clocks that are
currently not defined, which will need to get introduced in the future
PWM and PCM were just the last in this series.


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