sparc64: Add some more commentary to __raw_local_irq_save()

Suggested by Peter Zijlstra

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/sparc/include/asm/irqflags_64.h b/arch/sparc/include/asm/irqflags_64.h
index a16e94c4b149..bfa1ea45b4cd 100644
--- a/arch/sparc/include/asm/irqflags_64.h
+++ b/arch/sparc/include/asm/irqflags_64.h
@@ -80,6 +80,13 @@ static inline unsigned long __raw_local_irq_save(void)
 
         /* 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"