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/Kconfig

@@ -2,6 +2,8 @@ menu "Device Drivers"
 
 source "drivers/core/Kconfig"
 
+source "drivers/cpu/Kconfig"
+
 source "drivers/demo/Kconfig"
 
 source "drivers/pci/Kconfig"

drivers/Makefile

@@ -3,6 +3,7 @@ obj-$(CONFIG_DM_DEMO) += demo/
 obj-$(CONFIG_BIOSEMU) += bios_emulator/
 obj-y += block/
 obj-$(CONFIG_BOOTCOUNT_LIMIT) += bootcount/
+obj-$(CONFIG_CPU) += cpu/
 obj-y += crypto/
 obj-$(CONFIG_FPGA) += fpga/
 obj-y += hwmon/

drivers/cpu/Kconfig

+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

+#
+# 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

+/*
+ * 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,
+};

include/cpu.h

+/*
+ * Copyright (c) 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __CPU_H
+#define __CPU_H
+
+/**
+ * struct cpu_platdata - platform data for a CPU
+ *
+ * This can be accessed with dev_get_parent_platdata() for any UCLASS_CPU
+ * device.
+ *
+ * @cpu_id:	Platform-specific way of identifying the CPU.
+ */
+struct cpu_platdata {
+	int cpu_id;
+};
+
+/* CPU features - mostly just a placeholder for now */
+enum {
+	CPU_FEAT_L1_CACHE	= 0,	/* Supports level 1 cache */
+	CPU_FEAT_MMU		= 1,	/* Supports virtual memory */
+
+	CPU_FEAT_COUNT,
+};
+
+/**
+ * struct cpu_info - Information about a CPU
+ *
+ * @cpu_freq:	Current CPU frequency in Hz
+ * @features:	Flags for supported CPU features
+ */
+struct cpu_info {
+	ulong cpu_freq;
+	ulong features;
+};
+
+struct cpu_ops {
+	/**
+	 * get_desc() - Get a description string for a CPU
+	 *
+	 * @dev:	Device to check (UCLASS_CPU)
+	 * @buf:	Buffer to place string
+	 * @size:	Size of string space
+	 * @return 0 if OK, -ENOSPC if buffer is too small, other -ve on error
+	 */
+	int (*get_desc)(struct udevice *dev, char *buf, int size);
+
+	/**
+	 * get_info() - Get information about a CPU
+	 *
+	 * @dev:	Device to check (UCLASS_CPU)
+	 * @info:	Returns CPU info
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*get_info)(struct udevice *dev, struct cpu_info *info);
+};
+
+#define cpu_get_ops(dev)        ((struct cpu_ops *)(dev)->driver->ops)
+
+/**
+ * cpu_get_desc() - Get a description string for a CPU
+ *
+ * @dev:	Device to check (UCLASS_CPU)
+ * @buf:	Buffer to place string
+ * @size:	Size of string space
+ * @return 0 if OK, -ENOSPC if buffer is too small, other -ve on error
+ */
+int cpu_get_desc(struct udevice *dev, char *buf, int size);
+
+/**
+ * cpu_get_info() - Get information about a CPU
+ *
+ * @dev:	Device to check (UCLASS_CPU)
+ * @info:	Returns CPU info
+ * @return 0 if OK, -ve on error
+ */
+int cpu_get_info(struct udevice *dev, struct cpu_info *info);
+
+#endif

include/dm/uclass-id.h

@@ -45,6 +45,7 @@ enum uclass_id {
 	UCLASS_USB_HUB,		/* USB hub */
 	UCLASS_USB_DEV_GENERIC,	/* USB generic device */
 	UCLASS_MASS_STORAGE,	/* Mass storage device */
+	UCLASS_CPU,		/* CPU, typically part of an SoC */
 
 	UCLASS_COUNT,
 	UCLASS_INVALID = -1,