On Mon, Sep 16, 2013 at 12:37:43PM -0600, Stephen Warren wrote: > 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. > Ok with me, if that is in line with other clock drivers. Guenter -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
