xref: /kernel/linux/linux-5.10/Documentation/devicetree/bindings/clock/nvidia,tegra124-car.txt

NVIDIA Tegra124 and Tegra132 Clock And Reset Controller

This binding uses the common clock binding:
Documentation/devicetree/bindings/clock/clock-bindings.txt

The CAR (Clock And Reset) Controller on Tegra is the HW module responsible
for muxing and gating Tegra's clocks, and setting their rates.

Required properties :
- compatible : Should be "nvidia,tegra124-car" or "nvidia,tegra132-car"
- reg : Should contain CAR registers location and length
- clocks : Should contain phandle and clock specifiers for two clocks:
  the 32 KHz "32k_in", and the board-specific oscillator "osc".
- #clock-cells : Should be 1.
  In clock consumers, this cell represents the clock ID exposed by the
  CAR. The assignments may be found in the header files
  <dt-bindings/clock/tegra124-car-common.h> (which covers IDs common
  to Tegra124 and Tegra132) and <dt-bindings/clock/tegra124-car.h>
  (for Tegra124-specific clocks).
- #reset-cells : Should be 1.
  In clock consumers, this cell represents the bit number in the CAR's
  array of CLK_RST_CONTROLLER_RST_DEVICES_* registers.
- nvidia,external-memory-controller : phandle of the EMC driver.

The node should contain a "emc-timings" subnode for each supported RAM type (see
field RAM_CODE in register PMC_STRAPPING_OPT_A).

Required properties for "emc-timings" nodes :
- nvidia,ram-code : Should contain the value of RAM_CODE this timing set
  is used for.

Each "emc-timings" node should contain a "timing" subnode for every supported
EMC clock rate.

Required properties for "timing" nodes :
- clock-frequency : Should contain the memory clock rate to which this timing
relates.
- nvidia,parent-clock-frequency : Should contain the rate at which the current
parent of the EMC clock should be running at this timing.
- clocks : Must contain an entry for each entry in clock-names.
  See ../clocks/clock-bindings.txt for details.
- clock-names : Must include the following entries:
  - emc-parent : the clock that should be the parent of the EMC clock at this
timing.

Example SoC include file:

/ {
	tegra_car: clock@60006000 {
		compatible = "nvidia,tegra124-car";
		reg = <0x60006000 0x1000>;
		#clock-cells = <1>;
		#reset-cells = <1>;
		nvidia,external-memory-controller = <&emc>;
	};

	usb@c5004000 {
		clocks = <&tegra_car TEGRA124_CLK_USB2>;
	};
};

Example board file:

/ {
	clocks {
		compatible = "simple-bus";
		#address-cells = <1>;
		#size-cells = <0>;

		osc: clock@0 {
			compatible = "fixed-clock";
			reg = <0>;
			#clock-cells = <0>;
			clock-frequency = <112400000>;
		};

		clk_32k: clock@1 {
			compatible = "fixed-clock";
			reg = <1>;
			#clock-cells = <0>;
			clock-frequency = <32768>;
		};
	};

	&tegra_car {
		clocks = <&clk_32k> <&osc>;
	};

	clock@60006000 {
		emc-timings-3 {
			nvidia,ram-code = <3>;

			timing-12750000 {
				clock-frequency = <12750000>;
				nvidia,parent-clock-frequency = <408000000>;
				clocks = <&tegra_car TEGRA124_CLK_PLL_P>;
				clock-names = "emc-parent";
			};
			timing-20400000 {
				clock-frequency = <20400000>;
				nvidia,parent-clock-frequency = <408000000>;
				clocks = <&tegra_car TEGRA124_CLK_PLL_P>;
				clock-names = "emc-parent";
			};
		};
	};
};