sparc64: Add some more commentary to __raw_local_irq_save()
Suggested by Peter Zijlstra
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/include/asm/irqflags_64.h b/arch/sparc/include/asm/irqflags_64.h
index a16e94c..bfa1ea4 100644
--- a/arch/sparc/include/asm/irqflags_64.h
+++ b/arch/sparc/include/asm/irqflags_64.h
@@ -80,6 +80,13 @@
/* Disable interrupts to PIL_NORMAL_MAX unless we already
* are using PIL_NMI, in which case PIL_NMI is retained.
+ *
+ * The only values we ever program into the %pil are 0,
+ * PIL_NORMAL_MAX and PIL_NMI.
+ *
+ * Since PIL_NMI is the largest %pil value and all bits are
+ * set in it (0xf), it doesn't matter what PIL_NORMAL_MAX
+ * actually is.
*/
__asm__ __volatile__(
"rdpr %%pil, %0\n\t"