* LPDDR2 SDRAM memories compliant to JEDEC JESD209-2

Required properties:
- compatible : Should be one of - "jedec,lpddr2-nvm", "jedec,lpddr2-s2",
  "jedec,lpddr2-s4"

  "ti,jedec-lpddr2-s2" should be listed if the memory part is LPDDR2-S2 type

  "ti,jedec-lpddr2-s4" should be listed if the memory part is LPDDR2-S4 type

  "ti,jedec-lpddr2-nvm" should be listed if the memory part is LPDDR2-NVM type

- density  : <u32> representing density in Mb (Mega bits)

- io-width : <u32> representing bus width. Possible values are 8, 16, and 32

Optional properties:

The following optional properties represent the minimum value of some AC
timing parameters of the DDR device in terms of number of clock cycles.
These values shall be obtained from the device data-sheet.
- tRRD-min-tck
- tWTR-min-tck
- tXP-min-tck
- tRTP-min-tck
- tCKE-min-tck
- tRPab-min-tck
- tRCD-min-tck
- tWR-min-tck
- tRASmin-min-tck
- tCKESR-min-tck
- tFAW-min-tck

Child nodes:
- The lpddr2 node may have one or more child nodes of type "lpddr2-timings".
  "lpddr2-timings" provides AC timing parameters of the device for
  a given speed-bin. The user may provide the timings for as many
  speed-bins as is required. Please see Documentation/devicetree/
  bindings/lpddr2/lpddr2-timings.txt for more information on "lpddr2-timings"

Example:

elpida_ECB240ABACN : lpddr2 {
	compatible	= "Elpida,ECB240ABACN","jedec,lpddr2-s4";
	density		= <2048>;
	io-width	= <32>;

	tRPab-min-tck	= <3>;
	tRCD-min-tck	= <3>;
	tWR-min-tck	= <3>;
	tRASmin-min-tck	= <3>;
	tRRD-min-tck	= <2>;
	tWTR-min-tck	= <2>;
	tXP-min-tck	= <2>;
	tRTP-min-tck	= <2>;
	tCKE-min-tck	= <3>;
	tCKESR-min-tck	= <3>;
	tFAW-min-tck	= <8>;

	timings_elpida_ECB240ABACN_400mhz: lpddr2-timings@0 {
		compatible	= "jedec,lpddr2-timings";
		min-freq	= <10000000>;
		max-freq	= <400000000>;
		tRPab		= <21000>;
		tRCD		= <18000>;
		tWR		= <15000>;
		tRAS-min	= <42000>;
		tRRD		= <10000>;
		tWTR		= <7500>;
		tXP		= <7500>;
		tRTP		= <7500>;
		tCKESR		= <15000>;
		tDQSCK-max	= <5500>;
		tFAW		= <50000>;
		tZQCS		= <90000>;
		tZQCL		= <360000>;
		tZQinit		= <1000000>;
		tRAS-max-ns	= <70000>;
	};

	timings_elpida_ECB240ABACN_200mhz: lpddr2-timings@1 {
		compatible	= "jedec,lpddr2-timings";
		min-freq	= <10000000>;
		max-freq	= <200000000>;
		tRPab		= <21000>;
		tRCD		= <18000>;
		tWR		= <15000>;
		tRAS-min	= <42000>;
		tRRD		= <10000>;
		tWTR		= <10000>;
		tXP		= <7500>;
		tRTP		= <7500>;
		tCKESR		= <15000>;
		tDQSCK-max	= <5500>;
		tFAW		= <50000>;
		tZQCS		= <90000>;
		tZQCL		= <360000>;
		tZQinit		= <1000000>;
		tRAS-max-ns	= <70000>;
	};

}
