arm64: perf: add debug patch logging framework

Provide a mechanism to track which msm perf patches
are present in a kernel. Some kernel branches do not
include all patches which causes problems trying
to debug perf issues. This framework provides a way
to keep track of which patches have been included
in a build.

Change-Id: I7d3e3022dcdec6204f8d2ba3c49fc37c674db221
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>
[satyap: trivial merge conflict resolution]
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>

2 files changed, 65 insertions, 1 deletions

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 474691f8b13a..55345faded87 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -31,7 +31,7 @@ arm64-obj-$(CONFIG_COMPAT)		+= sys32.o kuser32.o signal32.o 	\
 arm64-obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace.o entry-ftrace.o
 arm64-obj-$(CONFIG_MODULES)		+= arm64ksyms.o module.o
 arm64-obj-$(CONFIG_PERF_EVENTS)		+= perf_regs.o perf_callchain.o
-arm64-obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event.o
+arm64-obj-$(CONFIG_HW_PERF_EVENTS)	+= perf_event.o perf_debug.o
 arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)	+= hw_breakpoint.o
 arm64-obj-$(CONFIG_CPU_PM)		+= sleep.o suspend.o
 arm64-obj-$(CONFIG_CPU_IDLE)		+= cpuidle.o
diff --git a/arch/arm64/kernel/perf_debug.c b/arch/arm64/kernel/perf_debug.c
new file mode 100644
index 000000000000..bbcfb8c9b2f9
--- /dev/null
+++ b/arch/arm64/kernel/perf_debug.c
@@ -0,0 +1,64 @@
+/* Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <linux/debugfs.h>
+
+/*
+ * Subsequent patches should add an entry to end of this string.
+ * Format is incrementing sequence number followed by text of
+ * patch commit title with newline.
+ * Note trailing ';' is on its own line to simplify addition of
+ * future strings.
+ */
+static char *descriptions =
+	" 0 arm64: perf: add debug patch logging framework\n"
+;
+
+static ssize_t desc_read(struct file *fp, char __user *buf,
+			 size_t count, loff_t *pos)
+{
+	return simple_read_from_buffer(buf, count, pos, descriptions,
+				       strlen(descriptions));
+}
+
+static const struct file_operations perf_debug_desc_fops = {
+	.read = desc_read,
+};
+
+static int perf_debugfs_init(void)
+{
+	int ret = 0;
+	struct dentry *dir;
+	struct dentry *file;
+
+	dir = debugfs_create_dir("msm-perf-patches", NULL);
+	if (IS_ERR_OR_NULL(dir)) {
+		pr_err("failed to create msm-perf-patches dir in debugfs\n");
+		ret = PTR_ERR(dir);
+		goto init_exit;
+	}
+
+	file = debugfs_create_file("descriptions", 0444, dir, NULL,
+				   &perf_debug_desc_fops);
+	if (IS_ERR_OR_NULL(file)) {
+		debugfs_remove(dir);
+		pr_err("failed to create descriptions file for msm-perf-patches\n");
+		ret = PTR_ERR(file);
+		goto init_exit;
+	}
+
+init_exit:
+	return ret;
+}
+late_initcall(perf_debugfs_init);