On Tue, May 05, 2015 at 04:09:31PM -0700, Andrew Bresticker wrote: > On Tue, May 5, 2015 at 3:43 PM, James Hogan <james.ho...@imgtec.com> wrote: > > On Tue, May 05, 2015 at 03:16:23PM -0700, Andrew Bresticker wrote: > >> Hi James, > >> > >> On Tue, May 5, 2015 at 3:01 PM, James Hogan <james.ho...@imgtec.com> wrote: > >> > Hi Andrew, > >> > > >> > On Tue, Apr 07, 2015 at 03:04:16PM -0700, Andrew Bresticker wrote: > >> >> Add a binding document for the USB2.0 PHY found on the IMG Pistachio > >> >> SoC. > >> >> > >> >> Signed-off-by: Andrew Bresticker <abres...@chromium.org> > >> >> Cc: Rob Herring <robh...@kernel.org> > >> >> Cc: Pawel Moll <pawel.m...@arm.com> > >> >> Cc: Mark Rutland <mark.rutl...@arm.com> > >> >> Cc: Ian Campbell <ijc+devicet...@hellion.org.uk> > >> >> Cc: Kumar Gala <ga...@codeaurora.org> > >> >> --- > >> >> No changes from v1. > >> >> --- > >> >> .../devicetree/bindings/phy/pistachio-usb-phy.txt | 29 > >> >> ++++++++++++++++++++++ > >> >> include/dt-bindings/phy/phy-pistachio-usb.h | 16 ++++++++++++ > >> >> 2 files changed, 45 insertions(+) > >> >> create mode 100644 > >> >> Documentation/devicetree/bindings/phy/pistachio-usb-phy.txt > >> >> create mode 100644 include/dt-bindings/phy/phy-pistachio-usb.h > >> >> > >> >> diff --git > >> >> a/Documentation/devicetree/bindings/phy/pistachio-usb-phy.txt > >> >> b/Documentation/devicetree/bindings/phy/pistachio-usb-phy.txt > >> >> new file mode 100644 > >> >> index 0000000..afbc7e2 > >> >> --- /dev/null > >> >> +++ b/Documentation/devicetree/bindings/phy/pistachio-usb-phy.txt > >> >> @@ -0,0 +1,29 @@ > >> >> +IMG Pistachio USB PHY > >> >> +===================== > >> >> + > >> >> +Required properties: > >> >> +-------------------- > >> >> + - compatible: Must be "img,pistachio-usb-phy". > >> >> + - #phy-cells: Must be 0. See ./phy-bindings.txt for details. > >> >> + - clocks: Must contain an entry for each entry in clock-names. > >> >> + See ../clock/clock-bindings.txt for details. > >> >> + - clock-names: Must include "usb_phy". > >> >> + - img,cr-top: Must constain a phandle to the CR_TOP syscon node. > >> >> + - img,refclk: Indicates the reference clock source for the USB PHY. > >> >> + See <dt-bindings/phy/phy-pistachio-usb.h> for a list of valid > >> >> values. > >> > > >> > Possibly dumb question: why isn't the reference clock source specified > >> > in the normal ways like the "usb_phy" clock is? > >> > > >> > Does the value required here depend on what usb_phy clock gets muxed > >> > from or something? > >> > >> Right, the value indicates what clock "usb_phy" is: whether it comes > >> from the core clock controller, the XO crystal, or is some external > >> clock. It's a mux internal to the PHY. > > > > Okay. If its a software controllable mux, is there a particular reason > > the DT doesn't describe it as such, i.e. have all 3 clock inputs, and > > the driver somehow work out which to use? > > Well, I'm not sure how the driver would determine which clock to use > without a device-tree property like the one I've got here :). Also,
Does it make sense to just look for the "best" usable source clock based on the supported rates listed in fsel_rate_map[] (for some definition of "best" such as "fastest" / "slowest" / "first usable"), or are things just not that simple? I'm just wondering how the DT writer would decide, since it seems to come down to a policy decision rather than a description of the hardware, which should probably be avoided in DT bindings if possible. If it really can't be avoided, then fair enough. Cheers James
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