From 4a3390f1d3b71f0645eb281176f00cd0d5ac2dcb Mon Sep 17 00:00:00 2001 From: Sean Anderson Date: Wed, 24 Jun 2020 06:41:12 -0400 Subject: dm: Add support for simple-pm-bus This type of bus is used in Linux to designate buses which have power domains and/or clocks which need to be enabled before their child devices can be used. Because power domains are automatically enabled before probing in U-Boot, we just need to enable any clocks present. Signed-off-by: Sean Anderson Reviewed-by: Simon Glass --- doc/device-tree-bindings/bus/simple-pm-bus.txt | 44 ++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 doc/device-tree-bindings/bus/simple-pm-bus.txt (limited to 'doc') diff --git a/doc/device-tree-bindings/bus/simple-pm-bus.txt b/doc/device-tree-bindings/bus/simple-pm-bus.txt new file mode 100644 index 0000000000..6f15037131 --- /dev/null +++ b/doc/device-tree-bindings/bus/simple-pm-bus.txt @@ -0,0 +1,44 @@ +Simple Power-Managed Bus +======================== + +A Simple Power-Managed Bus is a transparent bus that doesn't need a real +driver, as it's typically initialized by the boot loader. + +However, its bus controller is part of a PM domain, or under the control of a +functional clock. Hence, the bus controller's PM domain and/or clock must be +enabled for child devices connected to the bus (either on-SoC or externally) +to function. + +While "simple-pm-bus" follows the "simple-bus" set of properties, as specified +in the Devicetree Specification, it is not an extension of "simple-bus". + + +Required properties: + - compatible: Must contain at least "simple-pm-bus". + Must not contain "simple-bus". + It's recommended to let this be preceded by one or more + vendor-specific compatible values. + - #address-cells, #size-cells, ranges: Must describe the mapping between + parent address and child address spaces. + +Optional platform-specific properties for clock or PM domain control (at least +one of them is required): + - clocks: Must contain a reference to the functional clock(s), + - power-domains: Must contain a reference to the PM domain. +Please refer to the binding documentation for the clock and/or PM domain +providers for more details. + + +Example: + + bsc: bus@fec10000 { + compatible = "renesas,bsc-sh73a0", "renesas,bsc", + "simple-pm-bus"; + #address-cells = <1>; + #size-cells = <1>; + ranges = <0 0 0x20000000>; + reg = <0xfec10000 0x400>; + interrupts = <0 39 IRQ_TYPE_LEVEL_HIGH>; + clocks = <&zb_clk>; + power-domains = <&pd_a4s>; + }; -- cgit v1.2.3