reset: Introduce TI System Control Interface (TI SCI) reset driver

Some TI Keystone 2 and K3 family of SoCs contain a system controller
(like the Power Management Micro Controller (PMMC) on 66AK2G SoCs and
the Device Management and Security Controller on AM65x SoCs) that manage
the low-level device control (like clocks, resets etc) for the various
hardware modules present on the SoC. These device control operations are
provided to the host processor OS through a communication protocol
called the TI System Control Interface (TI SCI) protocol.

This patch adds a reset driver that communicates to the system
controller over the TI SCI protocol for performing reset management of
various devices present on the SoC. Various reset functionalities are
achieved by the means of different TI SCI device operations provided by
the TI SCI framework.

This code is loosely based on the drivers/reset/reset-ti-sci.c driver of
the Linux kernel.

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>

1 files changed, 54 insertions, 0 deletions

diff --git a/doc/device-tree-bindings/reset/ti,sci-reset.txt b/doc/device-tree-bindings/reset/ti,sci-reset.txt
new file mode 100644
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+Texas Instruments TI SCI Reset Controller
+=========================================
+
+Some TI SoCs contain a system controller (like the SYSFW, etc...) that is
+responsible for controlling the state of the IPs that are present.
+Communication between the host processor running an OS and the system
+controller happens through a protocol known as TI SCI [1].
+
+[1] http://processors.wiki.ti.com/index.php/TISCI
+
+Reset Controller Node
+=====================
+The reset controller node represents the resets of various hardware modules
+present on the SoC managed by the SYSFW. Because this relies on the TI SCI
+protocol to communicate with the SYSFW it must be a child of the sysfw node.
+
+Required Properties:
+--------------------
+ - compatible: Must be "ti,sci-reset"
+ - #reset-cells: Must be 2. Please see the reset consumer node below for
+		 usage details.
+
+Example (AM65x):
+----------------
+	sysfw: sysfw {
+		compatible = "ti,am654-system-controller";
+		...
+		k3_reset: reset-controller {
+			compatible = "ti,sci-reset";
+			#reset-cells = <2>;
+		};
+	};
+
+Reset Consumers
+===============
+Each of the reset consumer nodes should have the following properties,
+in addition to their own properties.
+
+Required Properties:
+--------------------
+ - resets: A phandle and reset specifier pair, one pair for each reset signal
+	   that affects the device, or that the device manages. The phandle
+	   should point to the TI SCI reset controller node, and the reset
+	   specifier should have 2 cell-values. The first cell should contain
+	   the device ID. The second cell should contain the reset mask value
+	   used by system controller.
+
+Example (AM65x):
+----------------
+	uart2: serial@02800000 {
+		compatible = "ti,omap4-uart";
+		...
+		resets = <&k3_reset 5 1>;
+	};