From 766e6a4ec602d0c107553b91b3434fe9c03474f4 Mon Sep 17 00:00:00 2001 From: Grant Likely Date: Mon, 9 Apr 2012 14:50:06 -0500 Subject: clk: add DT clock binding support Based on work 1st by Ben Herrenschmidt and Jeremy Kerr, then by Grant Likely, this patch adds support to clk_get to allow drivers to retrieve clock data from the device tree. Platforms scan for clocks in DT with of_clk_init and a match table, and the register a provider through of_clk_add_provider. The provider's clk_src_get function will be called when a device references the provider's OF node for a clock reference. v6 (Rob Herring): - Return error values instead of NULL to match clock framework expectations v5 (Rob Herring): - Move from drivers/of into common clock subsystem - Squashed "dt/clock: add a simple provider get function" and "dt/clock: add function to get parent clock name" - Rebase to 3.4-rc1 - Drop CONFIG_OF_CLOCK and just use CONFIG_OF - Add missing EXPORT_SYMBOL to various functions - s/clock-output-name/clock-output-names/ - Define that fixed-clock binding is a single output v4 (Rob Herring): - Rework for common clk subsystem - Add of_clk_get_parent_name function v3: - Clarified documentation v2: - fixed errant ';' causing compile error - Editorial fixes from Shawn Guo - merged in adding lookup to clkdev - changed property names to match established convention. After working with the binding a bit it really made more sense to follow the lead of 'reg', 'gpios' and 'interrupts' by making the input simply 'clocks' & 'clock-names' instead of 'clock-input-*', and to only use clock-output* for the producer nodes. (Sorry Shawn, this will mean you need to change some code, but it should be trivial) - Add ability to inherit clocks from parent nodes by using an empty 'clock-ranges' property. Useful for busses. I could use some feedback on the new property name, 'clock-ranges' doesn't feel right to me. Signed-off-by: Grant Likely Signed-off-by: Rob Herring Reviewed-by: Shawn Guo Cc: Sascha Hauer Signed-off-by: Mike Turquette --- .../devicetree/bindings/clock/clock-bindings.txt | 117 +++++++++++++++++++++ 1 file changed, 117 insertions(+) create mode 100644 Documentation/devicetree/bindings/clock/clock-bindings.txt (limited to 'Documentation/devicetree/bindings/clock/clock-bindings.txt') diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt new file mode 100644 index 00000000000..eb65d417f8c --- /dev/null +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt @@ -0,0 +1,117 @@ +This binding is a work-in-progress, and are based on some experimental +work by benh[1]. + +Sources of clock signal can be represented by any node in the device +tree. Those nodes are designated as clock providers. Clock consumer +nodes use a phandle and clock specifier pair to connect clock provider +outputs to clock inputs. Similar to the gpio specifiers, a clock +specifier is an array of one more more cells identifying the clock +output on a device. The length of a clock specifier is defined by the +value of a #clock-cells property in the clock provider node. + +[1] http://patchwork.ozlabs.org/patch/31551/ + +==Clock providers== + +Required properties: +#clock-cells: Number of cells in a clock specifier; Typically 0 for nodes + with a single clock output and 1 for nodes with multiple + clock outputs. + +Optional properties: +clock-output-names: Recommended to be a list of strings of clock output signal + names indexed by the first cell in the clock specifier. + However, the meaning of clock-output-names is domain + specific to the clock provider, and is only provided to + encourage using the same meaning for the majority of clock + providers. This format may not work for clock providers + using a complex clock specifier format. In those cases it + is recommended to omit this property and create a binding + specific names property. + + Clock consumer nodes must never directly reference + the provider's clock-output-names property. + +For example: + + oscillator { + #clock-cells = <1>; + clock-output-names = "ckil", "ckih"; + }; + +- this node defines a device with two clock outputs, the first named + "ckil" and the second named "ckih". Consumer nodes always reference + clocks by index. The names should reflect the clock output signal + names for the device. + +==Clock consumers== + +Required properties: +clocks: List of phandle and clock specifier pairs, one pair + for each clock input to the device. Note: if the + clock provider specifies '0' for #clock-cells, then + only the phandle portion of the pair will appear. + +Optional properties: +clock-names: List of clock input name strings sorted in the same + order as the clocks property. Consumers drivers + will use clock-names to match clock input names + with clocks specifiers. +clock-ranges: Empty property indicating that child nodes can inherit named + clocks from this node. Useful for bus nodes to provide a + clock to their children. + +For example: + + device { + clocks = <&osc 1>, <&ref 0>; + clock-names = "baud", "register"; + }; + + +This represents a device with two clock inputs, named "baud" and "register". +The baud clock is connected to output 1 of the &osc device, and the register +clock is connected to output 0 of the &ref. + +==Example== + + /* external oscillator */ + osc: oscillator { + compatible = "fixed-clock"; + #clock-cells = <1>; + clock-frequency = <32678>; + clock-output-names = "osc"; + }; + + /* phase-locked-loop device, generates a higher frequency clock + * from the external oscillator reference */ + pll: pll@4c000 { + compatible = "vendor,some-pll-interface" + #clock-cells = <1>; + clocks = <&osc 0>; + clock-names = "ref"; + reg = <0x4c000 0x1000>; + clock-output-names = "pll", "pll-switched"; + }; + + /* UART, using the low frequency oscillator for the baud clock, + * and the high frequency switched PLL output for register + * clocking */ + uart@a000 { + compatible = "fsl,imx-uart"; + reg = <0xa000 0x1000>; + interrupts = <33>; + clocks = <&osc 0>, <&pll 1>; + clock-names = "baud", "register"; + }; + +This DT fragment defines three devices: an external oscillator to provide a +low-frequency reference clock, a PLL device to generate a higher frequency +clock signal, and a UART. + +* The oscillator is fixed-frequency, and provides one clock output, named "osc". +* The PLL is both a clock provider and a clock consumer. It uses the clock + signal generated by the external oscillator, and provides two output signals + ("pll" and "pll-switched"). +* The UART has its baud clock connected the external oscillator and its + register clock connected to the PLL clock (the "pll-switched" signal) -- cgit v1.2.3-70-g09d2