drivers: soc: sunxi: Introduce SoC driver to map SRAMs

The Allwinner SoCs have a handful of SRAM that can be either mapped to be
accessible by devices or the CPU.

That mapping is controlled by an SRAM controller, and that mapping might
not be set by the bootloader, for example if the device wasn't used at all,
or if we're using solutions like the U-Boot's Falcon Boot.

We could also imagine changing this at runtime for example to change the
mapping of these SRAMs to use them for suspend/resume or runtime memory
rate change, if that ever happens.

These use cases require some API in the kernel to control that mapping,
exported through a drivers/soc driver.

This driver also implement a debugfs file that shows the SRAM found in the
system, the current mapping and the SRAM that have been claimed by some
drivers in the kernel.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 72 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/soc/sunxi/sram.txt b/Documentation/devicetree/bindings/soc/sunxi/sram.txt
new file mode 100644
index 0000000..0676981
--- /dev/null
+++ b/Documentation/devicetree/bindings/soc/sunxi/sram.txt
@@ -0,0 +1,72 @@
+Allwinnner SoC SRAM controllers
+-----------------------------------------------------
+
+The SRAM controller found on most Allwinner devices is represented by
+a regular node for the SRAM controller itself, with sub-nodes
+reprensenting the SRAM handled by the SRAM controller.
+
+Controller Node
+---------------
+
+Required properties:
+- compatible : "allwinner,sun4i-a10-sram-controller"
+- reg : sram controller register offset + length
+
+SRAM nodes
+----------
+
+Each SRAM is described using the mmio-sram bindings documented in
+Documentation/devicetree/bindings/misc/sram.txt
+
+Each SRAM will have SRAM sections that are going to be handled by the
+SRAM controller as subnodes. These sections are represented following
+once again the representation described in the mmio-sram binding.
+
+The valid sections compatible are:
+    - allwinner,sun4i-a10-sram-a3-a4
+    - allwinner,sun4i-a10-sram-d
+
+Devices using SRAM sections
+---------------------------
+
+Some devices need to request to the SRAM controller to map an SRAM for
+their exclusive use.
+
+The relationship between such a device and an SRAM section is
+expressed through the allwinner,sram property, that will take a
+phandle and an argument.
+
+This valid values for this argument are:
+  - 0: CPU
+  - 1: Device
+
+Example
+-------
+sram-controller@01c00000 {
+	compatible = "allwinner,sun4i-a10-sram-controller";
+	reg = <0x01c00000 0x30>;
+	#address-cells = <1>;
+	#size-cells = <1>;
+	ranges;
+
+	sram_a: sram@00000000 {
+		compatible = "mmio-sram";
+		reg = <0x00000000 0xc000>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges = <0 0x00000000 0xc000>;
+
+		emac_sram: sram-section@8000 {
+			compatible = "allwinner,sun4i-a10-sram-a3-a4";
+			reg = <0x8000 0x4000>;
+			status = "disabled";
+		};
+	};
+};
+
+emac: ethernet@01c0b000 {
+	compatible = "allwinner,sun4i-a10-emac";
+	...
+
+	allwinner,sram = <&emac_sram 1>;
+};