Documentation: Add documentation for APM X-Gene clock binding

Documentation: Add documentation for APM X-Gene clock binding with PLL and
device clocks.

Signed-off-by: Loc Ho <lho@apm.com>
Signed-off-by: Kumar Sankaran <ksankaran@apm.com>
Signed-off-by: Vinayak Kale <vkale@apm.com>
Signed-off-by: Feng Kan <fkan@apm.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

diff --git a/Documentation/devicetree/bindings/clock/xgene.txt b/Documentation/devicetree/bindings/clock/xgene.txt
new file mode 100644 (file)
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+Device Tree Clock bindings for APM X-Gene
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be one of the following:
+       "apm,xgene-socpll-clock" - for a X-Gene SoC PLL clock
+       "apm,xgene-pcppll-clock" - for a X-Gene PCP PLL clock
+       "apm,xgene-device-clock" - for a X-Gene device clock
+
+Required properties for SoC or PCP PLL clocks:
+- reg : shall be the physical PLL register address for the pll clock.
+- clocks : shall be the input parent clock phandle for the clock. This should
+       be the reference clock.
+- #clock-cells : shall be set to 1.
+- clock-output-names : shall be the name of the PLL referenced by derive
+  clock.
+Optional properties for PLL clocks:
+- clock-names : shall be the name of the PLL. If missing, use the device name.
+
+Required properties for device clocks:
+- reg : shall be a list of address and length pairs describing the CSR
+         reset and/or the divider. Either may be omitted, but at least
+         one must be present.
+ - reg-names : shall be a string list describing the reg resource. This
+               may include "csr-reg" and/or "div-reg". If this property
+               is not present, the reg property is assumed to describe
+               only "csr-reg".
+- clocks : shall be the input parent clock phandle for the clock.
+- #clock-cells : shall be set to 1.
+- clock-output-names : shall be the name of the device referenced.
+Optional properties for device clocks:
+- clock-names : shall be the name of the device clock. If missing, use the
+                device name.
+- csr-offset : Offset to the CSR reset register from the reset address base.
+               Default is 0.
+- csr-mask : CSR reset mask bit. Default is 0xF.
+- enable-offset : Offset to the enable register from the reset address base.
+                  Default is 0x8.
+- enable-mask : CSR enable mask bit. Default is 0xF.
+- divider-offset : Offset to the divider CSR register from the divider base.
+                   Default is 0x0.
+- divider-width : Width of the divider register. Default is 0.
+- divider-shift : Bit shift of the divider register. Default is 0.
+
+For example:
+
+       pcppll: pcppll@17000100 {
+               compatible = "apm,xgene-pcppll-clock";
+               #clock-cells = <1>;
+               clocks = <&refclk 0>;
+               clock-names = "pcppll";
+               reg = <0x0 0x17000100 0x0 0x1000>;
+               clock-output-names = "pcppll";
+               type = <0>;
+       };
+
+       socpll: socpll@17000120 {
+               compatible = "apm,xgene-socpll-clock";
+               #clock-cells = <1>;
+               clocks = <&refclk 0>;
+               clock-names = "socpll";
+               reg = <0x0 0x17000120 0x0 0x1000>;
+               clock-output-names = "socpll";
+               type = <1>;
+       };
+
+       qmlclk: qmlclk {
+               compatible = "apm,xgene-device-clock";
+               #clock-cells = <1>;
+               clocks = <&socplldiv2 0>;
+               clock-names = "qmlclk";
+               reg = <0x0 0x1703C000 0x0 0x1000>;
+               reg-name = "csr-reg";
+               clock-output-names = "qmlclk";
+       };
+
+       ethclk: ethclk {
+               compatible = "apm,xgene-device-clock";
+               #clock-cells = <1>;
+               clocks = <&socplldiv2 0>;
+               clock-names = "ethclk";
+               reg = <0x0 0x17000000 0x0 0x1000>;
+               reg-names = "div-reg";
+               divider-offset = <0x238>;
+               divider-width = <0x9>;
+               divider-shift = <0x0>;
+               clock-output-names = "ethclk";
+       };
+
+       apbclk: apbclk {
+               compatible = "apm,xgene-device-clock";
+               #clock-cells = <1>;
+               clocks = <&ahbclk 0>;
+               clock-names = "apbclk";
+               reg = <0x0 0x1F2AC000 0x0 0x1000
+                       0x0 0x1F2AC000 0x0 0x1000>;
+               reg-names = "csr-reg", "div-reg";
+               csr-offset = <0x0>;
+               csr-mask = <0x200>;
+               enable-offset = <0x8>;
+               enable-mask = <0x200>;
+               divider-offset = <0x10>;
+               divider-width = <0x2>;
+               divider-shift = <0x0>;
+               flags = <0x8>;
+               clock-output-names = "apbclk";
+       };
+