mtd: mediatek: device tree bindings for MTK

Documentation support for Smart Device Gen1 type of NAND controllers
Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Documentation/devicetree/bindings/mtd/mtk-nand.txt

+MTK SoCs NAND FLASH controller (NFC) DT binding
+
+This file documents the device tree bindings for MTK SoCs NAND controllers.
+The functional split of the controller requires two drivers to operate:
+the nand controller interface driver and the ECC engine driver.
+
+The hardware description for both devices must be captured as device
+tree nodes.
+
+1) NFC NAND Controller Interface (NFI):
+=======================================
+
+The first part of NFC is NAND Controller Interface (NFI) HW.
+Required NFI properties:
+- compatible:			Should be "mediatek,mtxxxx-nfc".
+- reg:				Base physical address and size of NFI.
+- interrupts:			Interrupts of NFI.
+- clocks:			NFI required clocks.
+- clock-names:			NFI clocks internal name.
+- status:			Disabled default. Then set "okay" by platform.
+- ecc-engine:			Required ECC Engine node.
+- #address-cells:		NAND chip index, should be 1.
+- #size-cells:			Should be 0.
+
+Example:
+
+	nandc: nfi@1100d000 {
+		compatible = "mediatek,mt2701-nfc";
+		reg = <0 0x1100d000 0 0x1000>;
+		interrupts = <GIC_SPI 56 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&pericfg CLK_PERI_NFI>,
+			 <&pericfg CLK_PERI_NFI_PAD>;
+		clock-names = "nfi_clk", "pad_clk";
+		status = "disabled";
+		ecc-engine = <&bch>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+        };
+
+Platform related properties, should be set in {platform_name}.dts:
+- children nodes:	NAND chips.
+
+Children nodes properties:
+- reg:			Chip Select Signal, default 0.
+			Set as reg = <0>, <1> when need 2 CS.
+Optional:
+- nand-on-flash-bbt:	Store BBT on NAND Flash.
+- nand-ecc-mode:	the NAND ecc mode (check driver for supported modes)
+- nand-ecc-step-size:	Number of data bytes covered by a single ECC step.
+			valid values: 512 and 1024.
+			1024 is recommended for large page NANDs.
+- nand-ecc-strength:	Number of bits to correct per ECC step.
+			The valid values that the controller supports are: 4, 6,
+			8, 10, 12, 14, 16, 18, 20, 22, 24, 28, 32, 36, 40, 44,
+			48, 52, 56, 60.
+			The strength should be calculated as follows:
+			E = (S - F) * 8 / 14
+			S = O / (P / Q)
+				E :	nand-ecc-strength.
+				S :	spare size per sector.
+				F :	FDM size, should be in the range [1,8].
+					It is used to store free oob data.
+				O :	oob size.
+				P :	page size.
+				Q :	nand-ecc-step-size.
+			If the result does not match any one of the listed
+			choices above, please select the smaller valid value from
+			the list.
+			(otherwise the driver will do the adjustment at runtime)
+- pinctrl-names:	Default NAND pin GPIO setting name.
+- pinctrl-0:		GPIO setting node.
+
+Example:
+	&pio {
+		nand_pins_default: nanddefault {
+			pins_dat {
+				pinmux = <MT2701_PIN_111_MSDC0_DAT7__FUNC_NLD7>,
+					 <MT2701_PIN_112_MSDC0_DAT6__FUNC_NLD6>,
+					 <MT2701_PIN_114_MSDC0_DAT4__FUNC_NLD4>,
+					 <MT2701_PIN_118_MSDC0_DAT3__FUNC_NLD3>,
+					 <MT2701_PIN_121_MSDC0_DAT0__FUNC_NLD0>,
+					 <MT2701_PIN_120_MSDC0_DAT1__FUNC_NLD1>,
+					 <MT2701_PIN_113_MSDC0_DAT5__FUNC_NLD5>,
+					 <MT2701_PIN_115_MSDC0_RSTB__FUNC_NLD8>,
+					 <MT2701_PIN_119_MSDC0_DAT2__FUNC_NLD2>;
+				input-enable;
+				drive-strength = <MTK_DRIVE_8mA>;
+				bias-pull-up;
+			};
+
+			pins_we {
+				pinmux = <MT2701_PIN_117_MSDC0_CLK__FUNC_NWEB>;
+				drive-strength = <MTK_DRIVE_8mA>;
+				bias-pull-up = <MTK_PUPD_SET_R1R0_10>;
+			};
+
+			pins_ale {
+				pinmux = <MT2701_PIN_116_MSDC0_CMD__FUNC_NALE>;
+				drive-strength = <MTK_DRIVE_8mA>;
+				bias-pull-down = <MTK_PUPD_SET_R1R0_10>;
+			};
+		};
+	};
+
+	&nandc {
+		status = "okay";
+		pinctrl-names = "default";
+		pinctrl-0 = <&nand_pins_default>;
+		nand@0 {
+			reg = <0>;
+			nand-on-flash-bbt;
+			nand-ecc-mode = "hw";
+			nand-ecc-strength = <24>;
+			nand-ecc-step-size = <1024>;
+		};
+	};
+
+NAND chip optional subnodes:
+- Partitions, see Documentation/devicetree/bindings/mtd/partition.txt
+
+Example:
+	nand@0 {
+		partitions {
+			compatible = "fixed-partitions";
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			preloader@0 {
+				label = "pl";
+				read-only;
+				reg = <0x00000000 0x00400000>;
+			};
+			android@0x00400000 {
+				label = "android";
+				reg = <0x00400000 0x12c00000>;
+			};
+		};
+	};
+
+2) ECC Engine:
+==============
+
+Required BCH properties:
+- compatible:	Should be "mediatek,mtxxxx-ecc".
+- reg:		Base physical address and size of ECC.
+- interrupts:	Interrupts of ECC.
+- clocks:	ECC required clocks.
+- clock-names:	ECC clocks internal name.
+- status:	Disabled default. Then set "okay" by platform.
+
+Example:
+
+	bch: ecc@1100e000 {
+		compatible = "mediatek,mt2701-ecc";
+		reg = <0 0x1100e000 0 0x1000>;
+		interrupts = <GIC_SPI 55 IRQ_TYPE_LEVEL_LOW>;
+		clocks = <&pericfg CLK_PERI_NFI_ECC>;
+		clock-names = "nfiecc_clk";
+		status = "disabled";
+	};