[PATCH v3] MIPS: Make CP0 config registers readable via sysfs.

["Steven J. Hill" <sjhill@mips.com>]

From: "Steven J. Hill" <sjhill@mips.com>

Allow reading of CP0 config registers via sysfs for each core
in the system. The registers will show up in sysfs at the path:

   /sys/devices/system/cpu/cpuX/configX

Only CP0 config registers 0 through 7 are currently supported.

Signed-off-by: Steven J. Hill <sjhill@mips.com>
---
 arch/mips/kernel/Makefile |    1 +
 arch/mips/kernel/sysfs.c  |   68 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)
 create mode 100644 arch/mips/kernel/sysfs.c

diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index cc5eec6..0c3eb97 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -97,6 +97,7 @@ obj-$(CONFIG_PERF_EVENTS)     += perf_event.o
 obj-$(CONFIG_HW_PERF_EVENTS)   += perf_event_mipsxx.o
 
 obj-$(CONFIG_JUMP_LABEL)       += jump_label.o
+obj-y                          += sysfs.o
 
 ifeq ($(CONFIG_CPU_MIPS32), y)
 #
diff --git a/arch/mips/kernel/sysfs.c b/arch/mips/kernel/sysfs.c
new file mode 100644
index 0000000..4f26349
--- /dev/null
+++ b/arch/mips/kernel/sysfs.c
@@ -0,0 +1,68 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2012 MIPS Technologies, Inc.  All rights reserved.
+ */
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/cpu.h>
+#include <linux/percpu.h>
+
+#include <asm/page.h>
+
+/* Convenience macro */
+#define read_c0_config0()      read_c0_config()
+
+#define __BUILD_CP0_SYSFS(reg)                                 \
+static ssize_t show_config##reg(struct device *dev,            \
+               struct device_attribute *attr, char *buf)       \
+{                                                              \
+       int n = snprintf(buf, PAGE_SIZE-2, "%x\n",              \
+               read_c0_config##reg());                         \
+       return n;                                               \
+}                                                              \
+static DEVICE_ATTR(config##reg, 0444, show_config##reg, NULL);
+
+__BUILD_CP0_SYSFS(0)
+__BUILD_CP0_SYSFS(1)
+__BUILD_CP0_SYSFS(2)
+__BUILD_CP0_SYSFS(3)
+__BUILD_CP0_SYSFS(4)
+__BUILD_CP0_SYSFS(5)
+__BUILD_CP0_SYSFS(6)
+__BUILD_CP0_SYSFS(7)
+
+#define __CHECK_CONFIG_EXIST(reg)                      \
+if (ok)        {                                               \
+       device_create_file(dev, &dev_attr_config##reg); \
+       ok = read_c0_config##reg() & MIPS_CONF_M;       \
+}
+
+static void read_c0_registers(void *arg)
+{
+       struct device *dev = get_cpu_device(smp_processor_id());
+       int ok = 1;
+
+       __CHECK_CONFIG_EXIST(0);
+       __CHECK_CONFIG_EXIST(1);
+       __CHECK_CONFIG_EXIST(2);
+       __CHECK_CONFIG_EXIST(3);
+       __CHECK_CONFIG_EXIST(4);
+       __CHECK_CONFIG_EXIST(5);
+       __CHECK_CONFIG_EXIST(6);
+       __CHECK_CONFIG_EXIST(7);
+}
+
+static int __init mips_sysfs_registers(void)
+{
+       /* Not CPU hotplug safe. */
+#ifndef CONFIG_HOTPLUG_CPU
+       on_each_cpu(read_c0_registers, NULL, 1);
+       return 0;
+#else
+       return 1;
+#endif
+}
+late_initcall(mips_sysfs_registers);
-- 
1.7.9.5