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Diffstat (limited to 'Documentation/devicetree/bindings/bus/uniphier-system-bus.txt')
| -rw-r--r-- | Documentation/devicetree/bindings/bus/uniphier-system-bus.txt | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/bus/uniphier-system-bus.txt b/Documentation/devicetree/bindings/bus/uniphier-system-bus.txt new file mode 100644 index 000000000000..68ef80afff16 --- /dev/null +++ b/Documentation/devicetree/bindings/bus/uniphier-system-bus.txt @@ -0,0 +1,66 @@ +UniPhier System Bus + +The UniPhier System Bus is an external bus that connects on-board devices to +the UniPhier SoC. It is a simple (semi-)parallel bus with address, data, and +some control signals. It supports up to 8 banks (chip selects). + +Before any access to the bus, the bus controller must be configured; the bus +controller registers provide the control for the translation from the offset +within each bank to the CPU-viewed address. The needed setup includes the base +address, the size of each bank. Optionally, some timing parameters can be +optimized for faster bus access. + +Required properties: +- compatible: should be "socionext,uniphier-system-bus". +- reg: offset and length of the register set for the bus controller device. +- #address-cells: should be 2. The first cell is the bank number (chip select). + The second cell is the address offset within the bank. +- #size-cells: should be 1. +- ranges: should provide a proper address translation from the System Bus to + the parent bus. + +Note: +The address region(s) that can be assigned for the System Bus is implementation +defined. Some SoCs can use 0x00000000-0x0fffffff and 0x40000000-0x4fffffff, +while other SoCs can only use 0x40000000-0x4fffffff. There might be additional +limitations depending on SoCs and the boot mode. The address translation is +arbitrary as long as the banks are assigned in the supported address space with +the required alignment and they do not overlap one another. +For example, it is possible to map: + bank 0 to 0x42000000-0x43ffffff, bank 5 to 0x46000000-0x46ffffff +It is also possible to map: + bank 0 to 0x48000000-0x49ffffff, bank 5 to 0x44000000-0x44ffffff +There is no reason to stick to a particular translation mapping, but the +"ranges" property should provide a "reasonable" default that is known to work. +The software should initialize the bus controller according to it. + +Example: + + system-bus { + compatible = "socionext,uniphier-system-bus"; + reg = <0x58c00000 0x400>; + #address-cells = <2>; + #size-cells = <1>; + ranges = <1 0x00000000 0x42000000 0x02000000 + 5 0x00000000 0x46000000 0x01000000>; + + ethernet@1,01f00000 { + compatible = "smsc,lan9115"; + reg = <1 0x01f00000 0x1000>; + interrupts = <0 48 4> + phy-mode = "mii"; + }; + + uart@5,00200000 { + compatible = "ns16550a"; + reg = <5 0x00200000 0x20>; + interrupts = <0 49 4> + clock-frequency = <12288000>; + }; + }; + +In this example, + - the Ethernet device is connected at the offset 0x01f00000 of CS1 and + mapped to 0x43f00000 of the parent bus. + - the UART device is connected at the offset 0x00200000 of CS5 and + mapped to 0x46200000 of the parent bus. |