dt-bindings: ddr: Add bindings for LPDDR3 memories

Specifies the AC timing parameters of the LPDDR3 memory device.
Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

Documentation/devicetree/bindings/ddr/lpddr3-timings.txt

+* AC timing parameters of LPDDR3 memories for a given speed-bin.
+
+The structures are based on LPDDR2 and extended where needed.
+
+Required properties:
+- compatible : Should be "jedec,lpddr3-timings"
+- min-freq : minimum DDR clock frequency for the speed-bin. Type is <u32>
+- reg : maximum DDR clock frequency for the speed-bin. Type is <u32>
+
+Optional properties:
+
+The following properties represent AC timing parameters from the memory
+data-sheet of the device for a given speed-bin. All these properties are
+of type <u32> and the default unit is ps (pico seconds).
+- tRFC
+- tRRD
+- tRPab
+- tRPpb
+- tRCD
+- tRC
+- tRAS
+- tWTR
+- tWR
+- tRTP
+- tW2W-C2C
+- tR2R-C2C
+- tFAW
+- tXSR
+- tXP
+- tCKE
+- tCKESR
+- tMRD
+
+Example:
+
+timings_samsung_K3QF2F20DB_800mhz: lpddr3-timings@800000000 {
+	compatible	= "jedec,lpddr3-timings";
+	reg		= <800000000>; /* workaround: it shows max-freq */
+	min-freq	= <100000000>;
+	tRFC		= <65000>;
+	tRRD		= <6000>;
+	tRPab		= <12000>;
+	tRPpb		= <12000>;
+	tRCD		= <10000>;
+	tRC		= <33750>;
+	tRAS		= <23000>;
+	tWTR		= <3750>;
+	tWR		= <7500>;
+	tRTP		= <3750>;
+	tW2W-C2C	= <0>;
+	tR2R-C2C	= <0>;
+	tFAW		= <25000>;
+	tXSR		= <70000>;
+	tXP		= <3750>;
+	tCKE		= <3750>;
+	tCKESR		= <3750>;
+	tMRD		= <7000>;
+};

Documentation/devicetree/bindings/ddr/lpddr3.txt

+* LPDDR3 SDRAM memories compliant to JEDEC JESD209-3C
+
+Required properties:
+- compatible : Should be  - "jedec,lpddr3"
+- density  : <u32> representing density in Mb (Mega bits)
+- io-width : <u32> representing bus width. Possible values are 8, 16, 32, 64
+- #address-cells: Must be set to 1
+- #size-cells: Must be set to 0
+
+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.
+- tRFC-min-tck
+- tRRD-min-tck
+- tRPab-min-tck
+- tRPpb-min-tck
+- tRCD-min-tck
+- tRC-min-tck
+- tRAS-min-tck
+- tWTR-min-tck
+- tWR-min-tck
+- tRTP-min-tck
+- tW2W-C2C-min-tck
+- tR2R-C2C-min-tck
+- tWL-min-tck
+- tDQSCK-min-tck
+- tRL-min-tck
+- tFAW-min-tck
+- tXSR-min-tck
+- tXP-min-tck
+- tCKE-min-tck
+- tCKESR-min-tck
+- tMRD-min-tck
+
+Child nodes:
+- The lpddr3 node may have one or more child nodes of type "lpddr3-timings".
+  "lpddr3-timings" provides AC timing parameters of the device for
+  a given speed-bin. Please see Documentation/devicetree/
+  bindings/ddr/lpddr3-timings.txt for more information on "lpddr3-timings"
+
+Example:
+
+samsung_K3QF2F20DB: lpddr3 {
+	compatible	= "Samsung,K3QF2F20DB", "jedec,lpddr3";
+	density		= <16384>;
+	io-width	= <32>;
+	#address-cells	= <1>;
+	#size-cells	= <0>;
+
+	tRFC-min-tck		= <17>;
+	tRRD-min-tck		= <2>;
+	tRPab-min-tck		= <2>;
+	tRPpb-min-tck		= <2>;
+	tRCD-min-tck		= <3>;
+	tRC-min-tck		= <6>;
+	tRAS-min-tck		= <5>;
+	tWTR-min-tck		= <2>;
+	tWR-min-tck		= <7>;
+	tRTP-min-tck		= <2>;
+	tW2W-C2C-min-tck	= <0>;
+	tR2R-C2C-min-tck	= <0>;
+	tWL-min-tck		= <8>;
+	tDQSCK-min-tck		= <5>;
+	tRL-min-tck		= <14>;
+	tFAW-min-tck		= <5>;
+	tXSR-min-tck		= <12>;
+	tXP-min-tck		= <2>;
+	tCKE-min-tck		= <2>;
+	tCKESR-min-tck		= <2>;
+	tMRD-min-tck		= <5>;
+
+	timings_samsung_K3QF2F20DB_800mhz: lpddr3-timings@800000000 {
+		compatible	= "jedec,lpddr3-timings";
+		reg		= <800000000>; /* workaround: it shows max-freq */
+		min-freq	= <100000000>;
+		tRFC		= <65000>;
+		tRRD		= <6000>;
+		tRPab		= <12000>;
+		tRPpb		= <12000>;
+		tRCD		= <10000>;
+		tRC		= <33750>;
+		tRAS		= <23000>;
+		tWTR		= <3750>;
+		tWR		= <7500>;
+		tRTP		= <3750>;
+		tW2W-C2C	= <0>;
+		tR2R-C2C	= <0>;
+		tFAW		= <25000>;
+		tXSR		= <70000>;
+		tXP		= <3750>;
+		tCKE		= <3750>;
+		tCKESR		= <3750>;
+		tMRD		= <7000>;
+	};
+}