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+======================================================================
+Device tree bindings for the Aspeed Low Pin Count (LPC) Bus Controller
+======================================================================
+
+The LPC bus is a means to bridge a host CPU to a number of low-bandwidth
+peripheral devices, replacing the use of the ISA bus in the age of PCI[0]. The
+primary use case of the Aspeed LPC controller is as a slave on the bus
+(typically in a Baseboard Management Controller SoC), but under certain
+conditions it can also take the role of bus master.
+
+The LPC controller is represented as a multi-function device to account for the
+mix of functionality it provides. The principle split is between the register
+layout at the start of the I/O space which is, to quote the Aspeed datasheet,
+"basically compatible with the [LPC registers from the] popular BMC controller
+H8S/2168[1]", and everything else, where everything else is an eclectic
+collection of functions with a esoteric register layout. "Everything else",
+here labeled the "host" portion of the controller, includes, but is not limited
+to:
+
+* An IPMI Block Transfer[2] Controller
+
+* An LPC Host Controller: Manages LPC functions such as host vs slave mode, the
+ physical properties of some LPC pins, configuration of serial IRQs, and
+ APB-to-LPC bridging amonst other functions.
+
+* An LPC Host Interface Controller: Manages functions exposed to the host such
+ as LPC firmware hub cycles, configuration of the LPC-to-AHB mapping, UART
+ management and bus snoop configuration.
+
+* A set of SuperIO[3] scratch registers: Enables implementation of e.g. custom
+ hardware management protocols for handover between the host and baseboard
+ management controller.
+
+Additionally the state of the LPC controller influences the pinmux
+configuration, therefore the host portion of the controller is exposed as a
+syscon as a means to arbitrate access.
+
+[0] http://www.intel.com/design/chipsets/industry/25128901.pdf
+[1] https://www.renesas.com/en-sg/doc/products/mpumcu/001/rej09b0078_h8s2168.pdf?key=7c88837454702128622bee53acbda8f4
+[2] https://www.intel.com/content/dam/www/public/us/en/documents/product-briefs/ipmi-second-gen-interface-spec-v2-rev1-1.pdf
+[3] https://en.wikipedia.org/wiki/Super_I/O
+
+Required properties
+===================
+
+- compatible: One of:
+ "aspeed,ast2400-lpc", "simple-mfd"
+ "aspeed,ast2500-lpc", "simple-mfd"
+
+- reg: contains the physical address and length values of the Aspeed
+ LPC memory region.
+
+- #address-cells: <1>
+- #size-cells: <1>
+- ranges: Maps 0 to the physical address and length of the LPC memory
+ region
+
+Required LPC Child nodes
+========================
+
+BMC Node
+--------
+
+- compatible: One of:
+ "aspeed,ast2400-lpc-bmc"
+ "aspeed,ast2500-lpc-bmc"
+
+- reg: contains the physical address and length values of the
+ H8S/2168-compatible LPC controller memory region
+
+Host Node
+---------
+
+- compatible: One of:
+ "aspeed,ast2400-lpc-host", "simple-mfd", "syscon"
+ "aspeed,ast2500-lpc-host", "simple-mfd", "syscon"
+
+- reg: contains the address and length values of the host-related
+ register space for the Aspeed LPC controller
+
+- #address-cells: <1>
+- #size-cells: <1>
+- ranges: Maps 0 to the address and length of the host-related LPC memory
+ region
+
+Example:
+
+lpc: lpc@1e789000 {
+ compatible = "aspeed,ast2500-lpc", "simple-mfd";
+ reg = <0x1e789000 0x1000>;
+
+ #address-cells = <1>;
+ #size-cells = <1>;
+ ranges = <0x0 0x1e789000 0x1000>;
+
+ lpc_bmc: lpc-bmc@0 {
+ compatible = "aspeed,ast2500-lpc-bmc";
+ reg = <0x0 0x80>;
+ };
+
+ lpc_host: lpc-host@80 {
+ compatible = "aspeed,ast2500-lpc-host", "simple-mfd", "syscon";
+ reg = <0x80 0x1e0>;
+ reg-io-width = <4>;
+
+ #address-cells = <1>;
+ #size-cells = <1>;
+ ranges = <0x0 0x80 0x1e0>;
+ };
+};
+
+BMC Node Children
+==================
+
+
+Host Node Children
+==================
+
+LPC Host Interface Controller
+-------------------
+
+The LPC Host Interface Controller manages functions exposed to the host such as
+LPC firmware hub cycles, configuration of the LPC-to-AHB mapping, UART
+management and bus snoop configuration.
+
+Required properties:
+
+- compatible: One of:
+ "aspeed,ast2400-lpc-ctrl";
+ "aspeed,ast2500-lpc-ctrl";
+
+- reg: contains offset/length values of the host interface controller
+ memory regions
+
+- clocks: contains a phandle to the syscon node describing the clocks.
+ There should then be one cell representing the clock to use
+
+Optional properties:
+
+- memory-region: A phandle to a reserved_memory region to be used for the LPC
+ to AHB mapping
+
+- flash: A phandle to the SPI flash controller containing the flash to
+ be exposed over the LPC to AHB mapping
+
+Example:
+
+lpc-host@80 {
+ lpc_ctrl: lpc-ctrl@0 {
+ compatible = "aspeed,ast2500-lpc-ctrl";
+ reg = <0x0 0x80>;
+ clocks = <&syscon ASPEED_CLK_GATE_LCLK>;
+ memory-region = <&flash_memory>;
+ flash = <&spi>;
+ };
+};
+
+LPC Host Controller
+-------------------
+
+The Aspeed LPC Host Controller configures the Low Pin Count (LPC) bus behaviour
+between the host and the baseboard management controller. The registers exist
+in the "host" portion of the Aspeed LPC controller, which must be the parent of
+the LPC host controller node.
+
+Required properties:
+
+- compatible: One of:
+ "aspeed,ast2400-lhc";
+ "aspeed,ast2500-lhc";
+
+- reg: contains offset/length values of the LHC memory regions. In the
+ AST2400 and AST2500 there are two regions.
+
+Example:
+
+lhc: lhc@20 {
+ compatible = "aspeed,ast2500-lhc";
+ reg = <0x20 0x24 0x48 0x8>;
+};
+
+LPC reset control
+-----------------
+
+The UARTs present in the ASPEED SoC can have their resets tied to the reset
+state of the LPC bus. Some systems may chose to modify this configuration.
+
+Required properties:
+
+ - compatible: "aspeed,ast2500-lpc-reset" or
+ "aspeed,ast2400-lpc-reset"
+ - reg: offset and length of the IP in the LHC memory region
+ - #reset-controller indicates the number of reset cells expected
+
+Example:
+
+lpc_reset: reset-controller@18 {
+ compatible = "aspeed,ast2500-lpc-reset";
+ reg = <0x18 0x4>;
+ #reset-cells = <1>;
+};