dm: Implement a CPU uclass

It is useful to be able to keep track of the available CPUs in a multi-CPU
system. This uclass is mostly intended for use with SMP systems.

The uclass provides methods for getting basic information about each CPU.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/cpu/Kconfig

@@ -0,0 +1,8 @@
+config CPU
+	bool "Enable CPU drivers using Driver Model"
+	help
+	  This allows drivers to be provided for CPUs and their type to be
+	  specified in the board's device tree. For boards which support
+	  multiple CPUs, then normally have to be set up in U-Boot so that
+	  they can work correctly in the OS. This provides a framework for
+	  finding out information about available CPUs and making changes.

drivers/cpu/Makefile

@@ -0,0 +1,7 @@
+#
+# Copyright (c) 2015 Google, Inc
+# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
+#
+# SPDX-License-Identifier:      GPL-2.0+
+#
+obj-$(CONFIG_CPU) += cpu-uclass.o

drivers/cpu/cpu-uclass.c

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <cpu.h>
+#include <dm.h>
+#include <dm/lists.h>
+#include <dm/root.h>
+
+int cpu_get_desc(struct udevice *dev, char *buf, int size)
+{
+	struct cpu_ops *ops = cpu_get_ops(dev);
+
+	if (!ops->get_desc)
+		return -ENOSYS;
+
+	return ops->get_desc(dev, buf, size);
+}
+
+int cpu_get_info(struct udevice *dev, struct cpu_info *info)
+{
+	struct cpu_ops *ops = cpu_get_ops(dev);
+
+	if (!ops->get_desc)
+		return -ENOSYS;
+
+	return ops->get_info(dev, info);
+}
+
+U_BOOT_DRIVER(cpu_bus) = {
+	.name	= "cpu_bus",
+	.id	= UCLASS_SIMPLE_BUS,
+	.per_child_platdata_auto_alloc_size = sizeof(struct cpu_platdata),
+};
+
+static int uclass_cpu_init(struct uclass *uc)
+{
+	struct udevice *dev;
+	int node;
+	int ret;
+
+	node = fdt_path_offset(gd->fdt_blob, "/cpus");
+	if (node < 0)
+		return 0;
+
+	ret = device_bind_driver_to_node(dm_root(), "cpu_bus", "cpus", node,
+					 &dev);
+
+	return ret;
+}
+
+UCLASS_DRIVER(cpu) = {
+	.id		= UCLASS_CPU,
+	.name		= "cpu",
+	.flags		= DM_UC_FLAG_SEQ_ALIAS,
+	.init		= uclass_cpu_init,
+};