On 09/16/2013 11:35 AM, Guenter Roeck wrote: > On Mon, Sep 16, 2013 at 10:59:58AM -0600, Stephen Warren wrote: >> On 09/16/2013 10:49 AM, Guenter Roeck wrote: >>> On Mon, Sep 16, 2013 at 10:34:28AM -0600, Stephen Warren wrote: >>>> On 09/12/2013 06:55 PM, Soren Brinkmann wrote: >>>>> Add a driver for SILabs 570, 571, 598, 599 programmable oscillators. >>>>> The devices generate low-jitter clock signals and are reprogrammable via >>>>> an I2C interface. ... >>>>> +Optional properties: >>>>> + - initial-fout: Initial output frequency to set during probe >>>> >>>> "probe" is a Linux-specific concept. This property should be removed. If >>>> the driver is asked to set a specific frequency, it should do so, but I >>>> don't think it should program something pro-actively just because it >>>> starts up. >>>> >>>> If this property is acceptable, it'd be better to describe it more along >>>> the lines of the following: >>>> >>>> initial-fout: The frequency at which the system requires the clock to >>>> operate. >>> >>> It should probably be something like "clock-frequency". In many use cases >>> the programmed frequency is set to a constant frequency at system startup >>> and never changed, similar to other clocks. >> >> I was going to suggest that too, but re-considered since I think >> clock-frequency is more appropriate for fixed-frequency clocks, rather >> than to specify the value at which a programmable clock generator should >> operate? >> >> I don't think we have a good story yet for how to represent >> how-we-want-the-clock-tree-configured, as opposed to representing the HW >> itself (which is what DT should be more about). > > In many cases the chip _is_ used to generate a fixed frequency, so we will > have to have a means to describe it. That it _can_ be used differently is a > different matter. After all, that is true for many clock generators. Perhaps if clock-frequency is specified, the driver should refuse to provide anything else. If clock-frequency isn't specified, the driver shouldn't touch the HW when it initializes, but should honor any requests that come in from other drivers? That would maintain what I feel is clock-frequency's connection to being a fixed clock. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
