dt-bindings: mtd: add Marvell NAND controller documentation
Document the legacy and the new bindings for Marvell NAND controller. The pxa3xx_nand.c driver does only support legacy bindings, which are incomplete and inaccurate. A rework of this controller (called marvell_nand.c) does support both. Signed-off-by: Miquel Raynal <miquel.raynal@free-electrons.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
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Miquel Raynal
Boris Brezillon
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Marvell NAND Flash Controller (NFC)
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Required properties:
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- compatible: can be one of the following:
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* "marvell,armada-8k-nand-controller"
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* "marvell,armada370-nand-controller"
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* "marvell,pxa3xx-nand-controller"
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* "marvell,armada-8k-nand" (deprecated)
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* "marvell,armada370-nand" (deprecated)
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* "marvell,pxa3xx-nand" (deprecated)
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Compatibles marked deprecated support only the old bindings described
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at the bottom.
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- reg: NAND flash controller memory area.
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- #address-cells: shall be set to 1. Encode the NAND CS.
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- #size-cells: shall be set to 0.
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- interrupts: shall define the NAND controller interrupt.
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- clocks: shall reference the NAND controller clock.
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- marvell,system-controller: Set to retrieve the syscon node that handles
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NAND controller related registers (only required with the
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"marvell,armada-8k-nand[-controller]" compatibles).
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Optional properties:
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- label: see partition.txt. New platforms shall omit this property.
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- dmas: shall reference DMA channel associated to the NAND controller.
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This property is only used with "marvell,pxa3xx-nand[-controller]"
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compatible strings.
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- dma-names: shall be "rxtx".
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This property is only used with "marvell,pxa3xx-nand[-controller]"
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compatible strings.
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Optional children nodes:
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Children nodes represent the available NAND chips.
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Required properties:
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- reg: shall contain the native Chip Select ids (0-3).
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- nand-rb: see nand.txt (0-1).
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Optional properties:
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- marvell,nand-keep-config: orders the driver not to take the timings
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from the core and leaving them completely untouched. Bootloader
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timings will then be used.
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- label: MTD name.
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- nand-on-flash-bbt: see nand.txt.
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- nand-ecc-mode: see nand.txt. Will use hardware ECC if not specified.
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- nand-ecc-algo: see nand.txt. This property is essentially useful when
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not using hardware ECC. Howerver, it may be added when using hardware
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ECC for clarification but will be ignored by the driver because ECC
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mode is chosen depending on the page size and the strength required by
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the NAND chip. This value may be overwritten with nand-ecc-strength
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property.
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- nand-ecc-strength: see nand.txt.
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- nand-ecc-step-size: see nand.txt. Marvell's NAND flash controller does
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use fixed strength (1-bit for Hamming, 16-bit for BCH), so the actual
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step size will shrink or grow in order to fit the required strength.
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Step sizes are not completely random for all and follow certain
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patterns described in AN-379, "Marvell SoC NFC ECC".
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See Documentation/devicetree/bindings/mtd/nand.txt for more details on
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generic bindings.
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Example:
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nand_controller: nand-controller@d0000 {
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compatible = "marvell,armada370-nand-controller";
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reg = <0xd0000 0x54>;
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#address-cells = <1>;
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#size-cells = <0>;
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interrupts = <GIC_SPI 84 IRQ_TYPE_LEVEL_HIGH>;
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clocks = <&coredivclk 0>;
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nand@0 {
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reg = <0>;
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label = "main-storage";
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nand-rb = <0>;
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nand-ecc-mode = "hw";
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marvell,nand-keep-config;
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nand-on-flash-bbt;
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nand-ecc-strength = <4>;
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nand-ecc-step-size = <512>;
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partitions {
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compatible = "fixed-partitions";
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#address-cells = <1>;
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#size-cells = <1>;
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partition@0 {
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label = "Rootfs";
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reg = <0x00000000 0x40000000>;
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};
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};
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};
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};
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Note on legacy bindings: One can find, in not-updated device trees,
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bindings slightly different than described above with other properties
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described below as well as the partitions node at the root of a so
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called "nand" node (without clear controller/chip separation).
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Legacy properties:
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- marvell,nand-enable-arbiter: To enable the arbiter, all boards blindly
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used it, this bit was set by the bootloader for many boards and even if
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it is marked reserved in several datasheets, it might be needed to set
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it (otherwise it is harmless) so whether or not this property is set,
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the bit is selected by the driver.
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- num-cs: Number of chip-select lines to use, all boards blindly set 1
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to this and for a reason, other values would have failed. The value of
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this property is ignored.
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Example:
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nand0: nand@43100000 {
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compatible = "marvell,pxa3xx-nand";
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reg = <0x43100000 90>;
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interrupts = <45>;
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dmas = <&pdma 97 0>;
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dma-names = "rxtx";
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#address-cells = <1>;
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marvell,nand-keep-config;
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marvell,nand-enable-arbiter;
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num-cs = <1>;
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/* Partitions (optional) */
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};
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