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 <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 44 insertions, 0 deletions

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 00000000000..6f15037131e
--- /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>;
+	};