diff options
| -rw-r--r-- | Documentation/devicetree/bindings/bus/nvidia,tegra20-gmi.txt | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/bus/nvidia,tegra20-gmi.txt b/Documentation/devicetree/bindings/bus/nvidia,tegra20-gmi.txt new file mode 100644 index 000000000000..83b0e54f727c --- /dev/null +++ b/Documentation/devicetree/bindings/bus/nvidia,tegra20-gmi.txt @@ -0,0 +1,132 @@ +Device tree bindings for NVIDIA Tegra Generic Memory Interface bus + +The Generic Memory Interface bus enables memory transfers between internal and +external memory. Can be used to attach various high speed devices such as +synchronous/asynchronous NOR, FPGA, UARTS and more. + +The actual devices are instantiated from the child nodes of a GMI node. + +Required properties: + - compatible : Should contain one of the following: + For Tegra20 must contain "nvidia,tegra20-gmi". + For Tegra30 must contain "nvidia,tegra30-gmi". + - reg: Should contain GMI controller registers location and length. + - clocks: Must contain an entry for each entry in clock-names. + - clock-names: Must include the following entries: "gmi" + - resets : Must contain an entry for each entry in reset-names. + - reset-names : Must include the following entries: "gmi" + - #address-cells: The number of cells used to represent physical base + addresses in the GMI address space. Should be 2. + - #size-cells: The number of cells used to represent the size of an address + range in the GMI address space. Should be 1. + - ranges: Must be set up to reflect the memory layout with three integer values + for each chip-select line in use (only one entry is supported, see below + comments): + <cs-number> <offset> <physical address of mapping> <size> + +Note that the GMI controller does not have any internal chip-select address +decoding, because of that chip-selects either need to be managed via software +or by employing external chip-select decoding logic. + +If external chip-select logic is used to support multiple devices it is assumed +that the devices use the same timing and so are probably the same type. It also +assumes that they can fit in the 256MB address range. In this case only one +child device is supported which represents the active chip-select line, see +examples for more insight. + +The chip-select number is decoded from the child nodes second address cell of +'ranges' property, if 'ranges' property is not present or empty chip-select will +then be decoded from the first cell of the 'reg' property. + +Optional child cs node properties: + + - nvidia,snor-data-width-32bit: Use 32bit data-bus, default is 16bit. + - nvidia,snor-mux-mode: Enable address/data MUX mode. + - nvidia,snor-rdy-active-before-data: Assert RDY signal one cycle before data. + If omitted it will be asserted with data. + - nvidia,snor-rdy-active-high: RDY signal is active high + - nvidia,snor-adv-active-high: ADV signal is active high + - nvidia,snor-oe-active-high: WE/OE signal is active high + - nvidia,snor-cs-active-high: CS signal is active high + + Note that there is some special handling for the timing values. + From Tegra TRM: + Programming 0 means 1 clock cycle: actual cycle = programmed cycle + 1 + + - nvidia,snor-muxed-width: Number of cycles MUX address/data asserted on the + bus. Valid values are 0-15, default is 1 + - nvidia,snor-hold-width: Number of cycles CE stays asserted after the + de-assertion of WR_N (in case of SLAVE/MASTER Request) or OE_N + (in case of MASTER Request). Valid values are 0-15, default is 1 + - nvidia,snor-adv-width: Number of cycles during which ADV stays asserted. + Valid values are 0-15, default is 1. + - nvidia,snor-ce-width: Number of cycles before CE is asserted. + Valid values are 0-15, default is 4 + - nvidia,snor-we-width: Number of cycles during which WE stays asserted. + Valid values are 0-15, default is 1 + - nvidia,snor-oe-width: Number of cycles during which OE stays asserted. + Valid values are 0-255, default is 1 + - nvidia,snor-wait-width: Number of cycles before READY is asserted. + Valid values are 0-255, default is 3 + +Example with two SJA1000 CAN controllers connected to the GMI bus. We wrap the +controllers with a simple-bus node since they are all connected to the same +chip-select (CS4), in this example external address decoding is provided: + +gmi@70090000 { + compatible = "nvidia,tegra20-gmi"; + reg = <0x70009000 0x1000>; + #address-cells = <2>; + #size-cells = <1>; + clocks = <&tegra_car TEGRA20_CLK_NOR>; + clock-names = "gmi"; + resets = <&tegra_car 42>; + reset-names = "gmi"; + ranges = <4 0 0xd0000000 0xfffffff>; + + status = "okay"; + + bus@4,0 { + compatible = "simple-bus"; + #address-cells = <1>; + #size-cells = <1>; + ranges = <0 4 0 0x40100>; + + nvidia,snor-mux-mode; + nvidia,snor-adv-active-high; + + can@0 { + reg = <0 0x100>; + ... + }; + + can@40000 { + reg = <0x40000 0x100>; + ... + }; + }; +}; + +Example with one SJA1000 CAN controller connected to the GMI bus +on CS4: + +gmi@70090000 { + compatible = "nvidia,tegra20-gmi"; + reg = <0x70009000 0x1000>; + #address-cells = <2>; + #size-cells = <1>; + clocks = <&tegra_car TEGRA20_CLK_NOR>; + clock-names = "gmi"; + resets = <&tegra_car 42>; + reset-names = "gmi"; + ranges = <4 0 0xd0000000 0xfffffff>; + + status = "okay"; + + can@4,0 { + reg = <4 0 0x100>; + nvidia,snor-mux-mode; + nvidia,snor-adv-active-high; + ... + }; +}; |