powerpc/pseries/htmdump: Add htm start support to htmdump module

Support starting of Hardware Trace Macro (HTM) function
via debugfs interface. Under debugfs folder
"/sys/kernel/debug/powerpc/htmdump", add file "htmstart".
The interface allows starting of htm via this file by
writing value "1". Also allows stopping of htm tracing by
writing value "0" to this file. Any other value returns
-EINVAL.

Signed-off-by: Athira Rajeev <[email protected]>
Tested-by: Venkat Rao Bagalkote <[email protected]>
Signed-off-by: Madhavan Srinivasan <[email protected]>
Link: https://patch.msgid.link/[email protected]

Author: Athira Rajeev

arch/powerpc/platforms/pseries/htmdump.c

@@ -17,6 +17,7 @@ static u32 nodalchipindex;
 static u32 coreindexonchip;
 static u32 htmtype;
 static u32 htmconfigure;
+static u32 htmstart;
 static struct dentry *htmdump_debugfs_dir;
 #define	HTM_ENABLE	1
 #define	HTM_DISABLE	0
@@ -157,7 +158,55 @@ static int htmconfigure_get(void *data, u64 *val)
 	return 0;
 }
 
+static int  htmstart_set(void *data, u64 val)
+{
+	long rc, ret;
+
+	/*
+	 * value as 1: start HTM
+	 * value as 0: stop HTM
+	 * Return -EINVAL for other values.
+	 */
+	if (val == HTM_ENABLE) {
+		/*
+		 * Invoke H_HTM call with:
+		 * - operation as htm start (H_HTM_OP_START)
+		 * - last three values are unused, hence set to zero
+		 */
+		rc = htm_hcall_wrapper(nodeindex, nodalchipindex, coreindexonchip,
+			   htmtype, H_HTM_OP_START, 0, 0, 0);
+
+	} else if (val == HTM_DISABLE) {
+		/*
+		 * Invoke H_HTM call with:
+		 * - operation as htm stop (H_HTM_OP_STOP)
+		 * - last three values are unused, hence set to zero
+		 */
+		rc = htm_hcall_wrapper(nodeindex, nodalchipindex, coreindexonchip,
+				htmtype, H_HTM_OP_STOP, 0, 0, 0);
+	} else
+		return -EINVAL;
+
+	ret = htm_return_check(rc);
+	if (ret <= 0) {
+		pr_debug("H_HTM hcall failed, returning %ld\n", ret);
+		return ret;
+	}
+
+	/* Set htmstart if H_HTM_OP_START/H_HTM_OP_STOP operation succeeds */
+	htmstart = val;
+
+	return 0;
+}
+
+static int htmstart_get(void *data, u64 *val)
+{
+	*val = htmstart;
+	return 0;
+}
+
 DEFINE_SIMPLE_ATTRIBUTE(htmconfigure_fops, htmconfigure_get, htmconfigure_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(htmstart_fops, htmstart_get, htmstart_set, "%llu\n");
 
 static int htmdump_init_debugfs(void)
 {
@@ -184,6 +233,7 @@ static int htmdump_init_debugfs(void)
 	 * Debugfs interface files to control HTM operations:
 	 */
 	debugfs_create_file("htmconfigure", 0600, htmdump_debugfs_dir, NULL, &htmconfigure_fops);
+	debugfs_create_file("htmstart", 0600, htmdump_debugfs_dir, NULL, &htmstart_fops);
 
 	return 0;
 }