memory: ti-aemif: add bindings for AEMIF driver

Add bindings for TI Async External Memory Interface (AEMIF) controller.

The Async External Memory Interface (EMIF16/AEMIF) controller is intended to
provide a glue-less interface to a variety of asynchronous memory devices like
ASRA M, NOR and NAND memory. A total of 256M bytes of any of these memories
can be accessed via 4 chip selects with 64M byte access per chip select.

We are not encoding CS number in reg property, it's memory partition number.
The CS number is encoded for Davinci NAND node using standalone property
"ti,davinci-chipselect" and we need to provide two memory ranges to it,
as result we can't encode CS number in "reg" for AEMIF child devices
(NAND/NOR/etc), as it will break bindings compatibility.

In this patch, NAND node is used just as an example of child node.
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: NIvan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/memory-controllers/ti-aemif.txt

+* Device tree bindings for Texas instruments AEMIF controller
+
+The Async External Memory Interface (EMIF16/AEMIF) controller is intended to
+provide a glue-less interface to a variety of asynchronous memory devices like
+ASRA M, NOR and NAND memory. A total of 256M bytes of any of these memories
+can be accessed at any given time via four chip selects with 64M byte access
+per chip select. Synchronous memories such as DDR1 SD RAM, SDR SDRAM
+and Mobile SDR are not supported.
+
+Documentation:
+Davinci DM646x - http://www.ti.com/lit/ug/sprueq7c/sprueq7c.pdf
+OMAP-L138 (DA850) - http://www.ti.com/lit/ug/spruh77a/spruh77a.pdf
+Kestone - http://www.ti.com/lit/ug/sprugz3a/sprugz3a.pdf
+
+Required properties:
+
+- compatible:		"ti,davinci-aemif"
+			"ti,keystone-aemif"
+			"ti,da850-aemif"
+
+- reg:			contains offset/length value for AEMIF control registers
+			space.
+
+- #address-cells:	Must be 2. The partition number has to be encoded in the
+			first address cell and it may accept values 0..N-1
+			(N - total number of partitions). It's recommended to
+			assign N-1 number for the control partition. The second
+			cell is the offset into the partition.
+
+- #size-cells:		Must be set to 1.
+
+- ranges:		Contains memory regions. There are two types of
+			ranges/partitions:
+			- CS-specific partition/range. If continuous, must be
+			set up to reflect the memory layout for 4 chipselects,
+			if not then additional range/partition can be added and
+			child device can select the proper one.
+			- control partition which is common for all CS
+			interfaces.
+
+- clocks:		the clock feeding the controller clock. Required only
+			if clock tree data present in device tree.
+			See clock-bindings.txt
+
+- clock-names:		clock name. It has to be "aemif". Required only if clock
+			tree data present in device tree, in another case don't
+			use it.
+			See clock-bindings.txt
+
+- clock-ranges:		Empty property indicating that child nodes can inherit
+			named clocks. Required only if clock tree data present
+			in device tree.
+			See clock-bindings.txt
+
+
+Child chip-select (cs) nodes contain the memory devices nodes connected to
+such as NOR (e.g. cfi-flash) and NAND (ti,davinci-nand, see davinci-nand.txt).
+There might be board specific devices like FPGAs.
+
+Required child cs node properties:
+
+- #address-cells:	Must be 2.
+
+- #size-cells:		Must be 1.
+
+- ranges:		Empty property indicating that child nodes can inherit
+			memory layout.
+
+- clock-ranges:		Empty property indicating that child nodes can inherit
+			named clocks. Required only if clock tree data present
+			in device tree.
+
+- ti,cs-chipselect:	number of chipselect. Indicates on the aemif driver
+			which chipselect is used for accessing the memory. For
+			compatibles "ti,davinci-aemif" and "ti,keystone-aemif"
+			it can be in range [0-3]. For compatible
+			"ti,da850-aemif" range is [2-5].
+
+Optional child cs node properties:
+
+- ti,cs-bus-width:		width of the asynchronous device's data bus
+				8 or 16 if not preset 8
+
+- ti,cs-select-strobe-mode:	enable/disable select strobe mode
+				In select strobe mode chip select behaves as
+				the strobe and is active only during the strobe
+				period. If present then enable.
+
+- ti,cs-extended-wait-mode:	enable/disable extended wait mode
+				if set, the controller monitors the EMIFWAIT pin
+				mapped to that chip select to determine if the
+				device wants to extend the strobe period. If
+				present then enable.
+
+- ti,cs-min-turnaround-ns:	minimum turn around time, ns
+				Time between the end of one asynchronous memory
+				access and the start of another asynchronous
+				memory access. This delay is not incurred
+				between a read followed by read or a write
+				followed by a write to same chip select.
+
+- ti,cs-read-setup-ns:		read setup width, ns
+				Time between the beginning of a memory cycle
+				and the activation of read strobe.
+				Minimum value is 1 (0 treated as 1).
+
+- ti,cs-read-strobe-ns:		read strobe width, ns
+				Time between the activation and deactivation of
+				the read strobe.
+				Minimum value is 1 (0 treated as 1).
+
+- ti,cs-read-hold-ns:		read hold width, ns
+				Time between the deactivation of the read
+				strobe and the end of the cycle (which may be
+				either an address change or the deactivation of
+				the chip select signal.
+				Minimum value is 1 (0 treated as 1).
+
+- ti,cs-write-setup-ns:		write setup width, ns
+				Time between the beginning of a memory cycle
+				and the activation of write strobe.
+				Minimum value is 1 (0 treated as 1).
+
+- ti,cs-write-strobe-ns:	write strobe width, ns
+				Time between the activation and deactivation of
+				the write strobe.
+				Minimum value is 1 (0 treated as 1).
+
+- ti,cs-write-hold-ns:		write hold width, ns
+				Time between the deactivation of the write
+				strobe and the end of the cycle (which may be
+				either an address change or the deactivation of
+				the chip select signal.
+				Minimum value is 1 (0 treated as 1).
+
+If any of the above parameters are absent, current parameter value will be taken
+from the corresponding HW reg.
+
+Example for aemif, davinci nand and nor flash chip select shown below.
+
+memory-controller@21000A00 {
+	compatible = "ti,davinci-aemif";
+	#address-cells = <2>;
+	#size-cells = <1>;
+	clocks = <&clkaemif 0>;
+	clock-names = "aemif";
+	clock-ranges;
+	reg = <0x21000A00 0x00000100>;
+	ranges = <0 0 0x70000000 0x10000000
+		  1 0 0x21000A00 0x00000100>;
+		  /*
+		   * Partition0: CS-specific memory range which is
+		   * implemented as continuous physical memory region
+		   * Partition1: control memory range
+		   */
+
+	nand:cs2 {
+		#address-cells = <2>;
+		#size-cells = <1>;
+		clock-ranges;
+		ranges;
+
+		ti,cs-chipselect = <2>;
+		/* all timings in nanoseconds */
+		ti,cs-min-turnaround-ns = <0>;
+		ti,cs-read-hold-ns = <7>;
+		ti,cs-read-strobe-ns = <42>;
+		ti,cs-read-setup-ns = <14>;
+		ti,cs-write-hold-ns = <7>;
+		ti,cs-write-strobe-ns = <42>;
+		ti,cs-write-setup-ns = <14>;
+
+		nand@0,0x8000000 {
+			compatible = "ti,davinci-nand";
+			reg = <0 0x8000000 0x4000000
+			       1 0x0000000 0x0000100>;
+			/*
+			 * Partition0, offset 0x8000000, size 0x4000000
+			 * Partition1, offset 0x0000000, size 0x0000100
+			 */
+
+			.. see davinci-nand.txt
+		};
+	};
+
+	nor:cs0 {
+		#address-cells = <2>;
+		#size-cells = <1>;
+		clock-ranges;
+		ranges;
+
+		ti,cs-chipselect = <0>;
+		/* all timings in nanoseconds */
+		ti,cs-min-turnaround-ns = <0>;
+		ti,cs-read-hold-ns = <8>;
+		ti,cs-read-strobe-ns = <40>;
+		ti,cs-read-setup-ns = <14>;
+		ti,cs-write-hold-ns = <7>;
+		ti,cs-write-strobe-ns = <40>;
+		ti,cs-write-setup-ns = <14>;
+		ti,cs-bus-width = <16>;
+
+		flash@0,0x0000000 {
+			compatible = "cfi-flash";
+			reg = <0 0x0000000 0x4000000>;
+
+			...
+		};
+	};
+};