[U-Boot] [RESEND PATCH 3/5] clk: add function to get peripheral ID

[Masahiro Yamada]

Hi Simon,


2015-12-28 23:20 GMT+09:00 Simon Glass <sjg at chromium.org>:
>> index 371784a..1efbaf2 100644
>> --- a/include/clk.h
>> +++ b/include/clk.h
>> @@ -49,6 +49,16 @@ struct clk_ops {
>>          * @return new clock rate in Hz, or -ve error code
>>          */
>>         ulong (*set_periph_rate)(struct udevice *dev, int periph, ulong rate);
>> +
>> +       /**
>> +        * get_id() - Get peripheral ID
>> +        *
>> +        * @dev:        clock provider
>> +        * @args_count: number of arguments
>> +        * @args:       arguments.  The meaning is driver specific.
>> +        * @return peripheral ID, or -ve error code
>> +        */
>> +       int (*get_id)(struct udevice *dev, int args_count, uint32_t *args);
>
> What are the arguments for? Who will use them? I wonder if the simple
> case you have is the only useful case for now?
>
> I think it would be better for the device tree parsing to happen
> within the uclass rather than requiring the caller to understand how
> it works. Here, we must obtain the arguments after the phandle and
> pass them to this function.

My intention was to make the interface as generic as possible.

It is true that most of drivers have '#clock-cells = <1>',
but I found some have '#clock-cells = <2>'.

Under linux/Documentation:

devicetree/bindings/clock/qoriq-clock.txt:When the clockgen node is a
clock provider, #clock-cells = <2>.
devicetree/bindings/clock/qoriq-clock.txt:              #clock-cells = <2>;
devicetree/bindings/clock/renesas,cpg-mssr.txt:         #clock-cells = <2>;
devicetree/bindings/clock/st,stm32-rcc.txt:             #clock-cells = <2>
devicetree/bindings/clock/ux500.txt:            #clock-cells = <2>;
devicetree/bindings/clock/ux500.txt:            #clock-cells = <2>;


So, my idea was to cover the simple case with clk_get_id_simple(),
but still allow such rare-case drivers to have their own .get_id() callback.

However, U-Boot might never be hit by such a case, and your simple one
meets our demand well enough.



-- 
Best Regards
Masahiro Yamada