Re: Programming a clock in the device tree

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

On 04/14/2016 01:15 AM, Peter Rosin wrote:
> Hi!
> 
> I'm trying to connect (in a device tree) a programmable clock
> to a device that does not expect the clock to need any
> programming.
> 
> I can hack this and add a clk_set_rate at the appropriate point
> in the driver for the clk consumer, but I was expecting to see
> some way of just adding a device tree node to get this done for
> me.
> 
> It just feels wrong to add this hack to the driver as the
> programmable clock might be needed for more than one device and
> the decisions by one driver might conflict with other needs (the
> driver in question can use a variety of clock rates, so the rate
> it should request is policy not belonging in a driver).
> 
> Adding a device tree frequency property to the driver in question
> is also a possibility, but that would need code duplication for
> other clock consumers as well, when someone wants to use those
> drivers in the way I'm now trying to use this driver.
> 
> I.e. I expected to see a driver, just like the fixed clock
> driver, but that programs a parent clock instead of just
> representing a fixed oscillator. Is there such a thing? If not,
> what is it that I'm not seeing? Because I just can't believe that
> I'm the first person to need this...

How about using assigned-{clocks, clock-parents, clock-rates}
properties in the clock provider node? Wouldn't it help in your
case? Documentation can be found in Documentation/devicetree/
bindings/clock/clock-bindings.txt


-- 
Regards,
Sylwester