On Fri, Jan 25, 2019 at 12:41 AM Stephen Boyd <sboyd@xxxxxxxxxx> wrote: > > Quoting Jonathan Cameron (2018-12-16 02:07:41) > > Rob, Clk experts, questions for you below. > > > > Jonathan > > > > > > On Thu, 13 Dec 2018 17:39:22 -0800 > > Stephen Boyd <sboyd@xxxxxxxxxx> wrote: > > > > > Quoting Jonathan Cameron (2018-12-08 07:29:54) > > > > On Thu, 6 Dec 2018 11:10:51 +0200 > > > > Mircea Caprioru <mircea.caprioru@xxxxxxxxxx> wrote: > > > > > > > > > This patch adds a clock to the state structure of ad7192 for getting the > > > > > external clock frequency. This modifications is in accordance with clock > > > > > framework dt bindings documentation. > > > > > > > > > > Signed-off-by: Mircea Caprioru <mircea.caprioru@xxxxxxxxxx> > > > > > > > > +cc Rob and the clk list for advise on how to do the binding for this one. > > > > > > > > It is basically 2 pins, you can put a clock in on one of them or connect > > > > a crystal across them. The driver has to set a register to say which is > > > > the case. > > > > > > > > Current proposal is two optional clocks (fall back to internal oscillator) > > > > but that doesn't seem to be commonly done, so I'm wondering if there > > > > is a 'standard' way to handle this sort of thing. > > > > > > > > > > I'm not sure I fully understand, but I think perhaps > > > assigned-clock-parents would work? Or does that not work because either > > > way some parent is assigned, either the crystal or the optional clk that > > > isn't a crystal? > > > > > My concern is they aren't really separate clock inputs. They are just different > > ways of providing the same fundamental clock. So I think we may want to just > > provide a single clock and have another dt binding to say what it is. > > > > So lots of ways we could do it, but I'm not sure what the right one to > > go with is! > > > > Sorry for getting back to this so late. Is the datasheet public for this > device? If so, any link to it? > Hey, Link is http://analog.com/ad7192 and that should resolve to the proper page, where the datasheet is available. [ General info: most [if not all] datasheets from Analog Devices can be found by concatenating "http://analog.com/ + "<part name>" ] But more directly, the link to the PDF is: https://www.analog.com/media/en/technical-documentation/data-sheets/AD7192.pdf Page 10 provides some description of the pins, page 20 the mode register for the clock, and page 32 a general description of the clock. If you search for MCLK1 or MCLK2 you should navigate pretty quick through the doc. The clock circuitry [the 2 pins] is common for all chips this driver supports [AD7190/2/3/5]. Thanks Alex > If it's two pins, and sometimes one pin is connected and other times two > pins are connected but a register needs to be set if the pins are > connected in one configuration or the other I would say your plan for a > DT property indicating how the pins are configured sounds good. Usually > the hardware can figure these things out itself so I find this sort of > odd, but if this is how it is then there's not much that we can do. > > It sounds like there aren't two different clk inputs to the device. > Given that information specifying two optional clks is incorrect because > there is only one 'slot' is the external clk source. >
