On Tue, Jan 17, 2017 at 02:53:02PM -0800, Tony Lindgren wrote: > Texas Instruments omap variant SoCs starting with omap4 have a clkctrl > clock controller instance for each interconnect target module. The clkctrl > controls functional and interface clocks for the module. > > The clkctrl clocks are currently handled by arch/arm/mach-omap2 hwmod code. > With this binding and a related clock device driver we can start moving the > clkctrl clock handling to live in drivers/clk/ti. > > Note that this binding allows keeping the clockdomain related parts out of > drivers/clock. The CLKCTCTRL and DYNAMICDEP registers can be handled by > a separate driver in drivers/soc/ti and genpd. If the clockdomain driver > needs to know it's clocks, we can just set the the clkctrl device > instances to be children of the related clockdomain device. > > Each clkctrl clock can have multiple optional gate clocks, and multiple > optional mux clocks. To represent this in device tree, it seems that > it is best done using four clock cells #clock-cells = <4> property. > > The reasons for using #clock-cells = <4> are: > > 1. We need to specify the clkctrl offset from the instance base. Otherwise > we end up with a large number of device tree nodes that need to be > patched when new clocks are discovered in a clkctrl clock with minor > hardware revision changes for example > > 2. On omap5 CM_L3INIT_USB_HOST_HS_CLKCTRL has ten OPTFCLKEN bits. So we > need to use a separate cell for optional gate clocks to avoid address > space conflicts > > 3. Some clkctrl instances can also also optional mux clocks. To address > them properly we need also a separate cell for the optional mux > clock index > > 4. The modulemode clock needs a flag passed to it for hardware or > software controlled mode > > There is probably no need to list input clocks for each clkctrl clock > instance in the binding. If we want to add them, the standard clocks > binding can be used for that. > > For hardware reference, see omap4430 TRM "Table 3-1312. L4PER_CM2 Registers > Mapping Summary" for example. It shows one instance of a clkctrl clock > controller with multiple clkctrl registers. > > Cc: Paul Walmsley <paul@xxxxxxxxx> > Cc: Rob Herring <robh@xxxxxxxxxx> > Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> > --- > > Changes from v1: > > - Use #clock-cells to avoid address space conflicts > > - Consider also optional mux clocks as pointed out by Tero > > --- > .../devicetree/bindings/clock/ti-clkctrl.txt | 57 ++++++++++++++++++++++ > 1 file changed, 57 insertions(+) > create mode 100644 Documentation/devicetree/bindings/clock/ti-clkctrl.txt Acked-by: Rob Herring <robh@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
