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Diffstat (limited to 'Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt')
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diff --git a/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt new file mode 100644 index 000000000000..653c90c34a71 --- /dev/null +++ b/Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt @@ -0,0 +1,156 @@ +Device tree bindings for MVEBU Device Bus controllers + +The Device Bus controller available in some Marvell's SoC allows to control +different types of standard memory and I/O devices such as NOR, NAND, and FPGA. +The actual devices are instantiated from the child nodes of a Device Bus node. + +Required properties: + + - compatible: Currently only Armada 370/XP SoC are supported, + with this compatible string: + + marvell,mvebu-devbus + + - reg: A resource specifier for the register space. + This is the base address of a chip select within + the controller's register space. + (see the example below) + + - #address-cells: Must be set to 1 + - #size-cells: Must be set to 1 + - ranges: Must be set up to reflect the memory layout with four + integer values for each chip-select line in use: + 0 <physical address of mapping> <size> + +Mandatory timing properties for child nodes: + +Read parameters: + + - devbus,turn-off-ps: Defines the time during which the controller does not + drive the AD bus after the completion of a device read. + This prevents contentions on the Device Bus after a read + cycle from a slow device. + + - devbus,bus-width: Defines the bus width (e.g. <16>) + + - devbus,badr-skew-ps: Defines the time delay from from A[2:0] toggle, + to read data sample. This parameter is useful for + synchronous pipelined devices, where the address + precedes the read data by one or two cycles. + + - devbus,acc-first-ps: Defines the time delay from the negation of + ALE[0] to the cycle that the first read data is sampled + by the controller. + + - devbus,acc-next-ps: Defines the time delay between the cycle that + samples data N and the cycle that samples data N+1 + (in burst accesses). + + - devbus,rd-setup-ps: Defines the time delay between DEV_CSn assertion to + DEV_OEn assertion. If set to 0 (default), + DEV_OEn and DEV_CSn are asserted at the same cycle. + This parameter has no affect on <acc-first-ps> parameter + (no affect on first data sample). Set <rd-setup-ps> + to a value smaller than <acc-first-ps>. + + - devbus,rd-hold-ps: Defines the time between the last data sample to the + de-assertion of DEV_CSn. If set to 0 (default), + DEV_OEn and DEV_CSn are de-asserted at the same cycle + (the cycle of the last data sample). + This parameter has no affect on DEV_OEn de-assertion. + DEV_OEn is always de-asserted the next cycle after + last data sampled. Also this parameter has no + affect on <turn-off-ps> parameter. + Set <rd-hold-ps> to a value smaller than <turn-off-ps>. + +Write parameters: + + - devbus,ale-wr-ps: Defines the time delay from the ALE[0] negation cycle + to the DEV_WEn assertion. + + - devbus,wr-low-ps: Defines the time during which DEV_WEn is active. + A[2:0] and Data are kept valid as long as DEV_WEn + is active. This parameter defines the setup time of + address and data to DEV_WEn rise. + + - devbus,wr-high-ps: Defines the time during which DEV_WEn is kept + inactive (high) between data beats of a burst write. + DEV_A[2:0] and Data are kept valid (do not toggle) for + <wr-high-ps> - <tick> ps. + This parameter defines the hold time of address and + data after DEV_WEn rise. + + - devbus,sync-enable: Synchronous device enable. + 1: True + 0: False + +An example for an Armada XP GP board, with a 16 MiB NOR device as child +is showed below. Note that the Device Bus driver is in charge of allocating +the mbus address decoding window for each of its child devices. +The window is created using the chip select specified in the child +device node together with the base address and size specified in the ranges +property. For instance, in the example below the allocated decoding window +will start at base address 0xf0000000, with a size 0x1000000 (16 MiB) +for chip select 0 (a.k.a DEV_BOOTCS). + +This address window handling is done in this mvebu-devbus only as a temporary +solution. It will be removed when the support for mbus device tree binding is +added. + +The reg property implicitly specifies the chip select as this: + + 0x10400: DEV_BOOTCS + 0x10408: DEV_CS0 + 0x10410: DEV_CS1 + 0x10418: DEV_CS2 + 0x10420: DEV_CS3 + +Example: + + devbus-bootcs@d0010400 { + status = "okay"; + ranges = <0 0xf0000000 0x1000000>; /* @addr 0xf0000000, size 0x1000000 */ + #address-cells = <1>; + #size-cells = <1>; + + /* Device Bus parameters are required */ + + /* Read parameters */ + devbus,bus-width = <8>; + devbus,turn-off-ps = <60000>; + devbus,badr-skew-ps = <0>; + devbus,acc-first-ps = <124000>; + devbus,acc-next-ps = <248000>; + devbus,rd-setup-ps = <0>; + devbus,rd-hold-ps = <0>; + + /* Write parameters */ + devbus,sync-enable = <0>; + devbus,wr-high-ps = <60000>; + devbus,wr-low-ps = <60000>; + devbus,ale-wr-ps = <60000>; + + flash@0 { + compatible = "cfi-flash"; + + /* 16 MiB */ + reg = <0 0x1000000>; + bank-width = <2>; + #address-cells = <1>; + #size-cells = <1>; + + /* + * We split the 16 MiB in two partitions, + * just as an example. + */ + partition@0 { + label = "First"; + reg = <0 0x800000>; + }; + + partition@800000 { + label = "Second"; + reg = <0x800000 0x800000>; + }; + }; + }; |