diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index 05728894..16ee6ce 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -452,6 +452,7 @@
 	NULL,				/* v */
 	&sysrq_showstate_blocked_op,	/* w */
 	/* x: May be registered on ppc/powerpc for xmon */
+	/* x: May be registered on sparc64 for global PMU dump */
 	NULL,				/* x */
 	/* y: May be registered on sparc64 for global register dump */
 	NULL,				/* y */