drivers: Add AXI uclass

Add a uclass for AXI (Advanced eXtensible Interface) busses, and a
driver for the gdsys IHS AXI bus on IHS FPGAs.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/axi.h

@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * (C) Copyright 2017
+ * Mario Six,  Guntermann & Drunck GmbH, mario.six@gdsys.cc
+ */
+
+#ifndef _AXI_H_
+#define _AXI_H_
+
+enum axi_size_t {
+	AXI_SIZE_8,
+	AXI_SIZE_16,
+	AXI_SIZE_32,
+};
+
+/**
+ * struct axi_ops - driver operations for AXI uclass
+ *
+ * Drivers should support these operations unless otherwise noted. These
+ * operations are intended to be used by uclass code, not directly from
+ * other code.
+ */
+struct axi_ops {
+	/**
+	 * read() - Read a single value from a specified address on a AXI bus
+	 *
+	 * @dev:	AXI bus to read from.
+	 * @address:	The address to read from.
+	 * @data:	Pointer to a variable that takes the data value read
+	 *		from the address on the AXI bus.
+	 * @size:	The size of the data to be read.
+	 * @return 0 if OK, -ve on error.
+	 */
+	int (*read)(struct udevice *dev, ulong address, void *data,
+		    enum axi_size_t size);
+
+	/**
+	 * write() - Write a single value to a specified address on a AXI bus
+	 *
+	 * @dev:	AXI bus to write to.
+	 * @address:	The address to write to.
+	 * @data:	Pointer to the data value to be written to the address
+	 *		on the AXI bus.
+	 * @size:	The size of the data to write.
+	 * @return 0 if OK, -ve on error.
+	 */
+	int (*write)(struct udevice *dev, ulong address, void *data,
+		     enum axi_size_t size);
+};
+
+#define axi_get_ops(dev)	((struct axi_ops *)(dev)->driver->ops)
+
+/**
+ * axi_read() - Read a single value from a specified address on a AXI bus
+ *
+ * @dev:	AXI bus to read from.
+ * @address:	The address to read from.
+ * @data:	Pointer to a variable that takes the data value read from the
+ *              address on the AXI bus.
+ * @size:	The size of the data to write.
+ * @return 0 if OK, -ve on error.
+ */
+int axi_read(struct udevice *dev, ulong address, void *data,
+	     enum axi_size_t size);
+
+/**
+ * axi_write() - Write a single value to a specified address on a AXI bus
+ *
+ * @dev:	AXI bus to write to.
+ * @address:	The address to write to.
+ * @data:	Pointer to the data value to be written to the address on the
+ *		AXI bus.
+ * @size:	The size of the data to write.
+ * @return 0 if OK, -ve on error.
+ */
+int axi_write(struct udevice *dev, ulong address, void *data,
+	      enum axi_size_t size);
+#endif