From: David S. Miller <davem@davemloft.net>
Date: Tue, 13 Apr 2010 08:50:43 +0000 (-0700)
Subject: sparc64: Add some more commentary to __raw_local_irq_save()
X-Git-Tag: v5.15~29841^2
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=c011f80ba0912486fe51dd2b3f71d9b33a151188;p=mirror_ubuntu-kernels.git

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 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"