ARM: imx6: report soc info via soc device

The patch enables soc bus infrastructure and adds a function
imx_soc_device_init() to report soc info via soc device interface for
imx6qdl and imx6sl.  With the support, user space can get soc related
info by looking at sysfs like below.

  $ cat /sys/devices/soc0/machine
  Freescale i.MX6 Quad SABRE Smart Device Board
  $ cat /sys/devices/soc0/family
  Freescale i.MX
  $ cat /sys/devices/soc0/soc_id
  i.MX6Q
  $ cat /sys/devices/soc0/revision
  1.2

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/cpu.c

@@ -1,6 +1,9 @@
 
 #include <linux/module.h>
 #include <linux/io.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/sys_soc.h>
 
 #include "hardware.h"
 #include "common.h"
@@ -56,3 +59,81 @@ void __init imx_set_aips(void __iomem *base)
 	reg = __raw_readl(base + 0x50) & 0x00FFFFFF;
 	__raw_writel(reg, base + 0x50);
 }
+
+struct device * __init imx_soc_device_init(void)
+{
+	struct soc_device_attribute *soc_dev_attr;
+	struct soc_device *soc_dev;
+	struct device_node *root;
+	const char *soc_id;
+	int ret;
+
+	soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
+	if (!soc_dev_attr)
+		return NULL;
+
+	soc_dev_attr->family = "Freescale i.MX";
+
+	root = of_find_node_by_path("/");
+	ret = of_property_read_string(root, "model", &soc_dev_attr->machine);
+	of_node_put(root);
+	if (ret)
+		goto free_soc;
+
+	switch (__mxc_cpu_type) {
+	case MXC_CPU_MX1:
+		soc_id = "i.MX1";
+		break;
+	case MXC_CPU_MX21:
+		soc_id = "i.MX21";
+		break;
+	case MXC_CPU_MX25:
+		soc_id = "i.MX25";
+		break;
+	case MXC_CPU_MX27:
+		soc_id = "i.MX27";
+		break;
+	case MXC_CPU_MX31:
+		soc_id = "i.MX31";
+		break;
+	case MXC_CPU_MX35:
+		soc_id = "i.MX35";
+		break;
+	case MXC_CPU_MX51:
+		soc_id = "i.MX51";
+		break;
+	case MXC_CPU_MX53:
+		soc_id = "i.MX53";
+		break;
+	case MXC_CPU_IMX6SL:
+		soc_id = "i.MX6SL";
+		break;
+	case MXC_CPU_IMX6DL:
+		soc_id = "i.MX6DL";
+		break;
+	case MXC_CPU_IMX6Q:
+		soc_id = "i.MX6Q";
+		break;
+	default:
+		soc_id = "Unknown";
+	}
+	soc_dev_attr->soc_id = soc_id;
+
+	soc_dev_attr->revision = kasprintf(GFP_KERNEL, "%d.%d",
+					   (imx_soc_revision >> 4) & 0xf,
+					   imx_soc_revision & 0xf);
+	if (!soc_dev_attr->revision)
+		goto free_soc;
+
+	soc_dev = soc_device_register(soc_dev_attr);
+	if (IS_ERR(soc_dev))
+		goto free_rev;
+
+	return soc_device_to_device(soc_dev);
+
+free_rev:
+	kfree(soc_dev_attr->revision);
+free_soc:
+	kfree(soc_dev_attr);
+	return NULL;
+}