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Re: [PATCH 2/6] TXx9: Microoptimize interrupt handlers

To: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Subject: Re: [PATCH 2/6] TXx9: Microoptimize interrupt handlers
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Wed, 03 Sep 2008 14:13:26 +0400
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to: <1220275361-5001-2-git-send-email-anemo@mba.ocn.ne.jp>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1220275361-5001-2-git-send-email-anemo@mba.ocn.ne.jp>
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Hello.

Atsushi Nemoto wrote:

The IOC interrupt status register on RBTX49XX only have 8 bits.  Use
8-bit version of __fls() to optimize interrupt handlers.

But doesn't the patch also change the result of toshiba_rbtx49{27|38}_irq_nested() if the register reads back as 0?

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 arch/mips/txx9/rbtx4927/irq.c   |    6 +++---
 arch/mips/txx9/rbtx4938/irq.c   |    8 ++++----
 include/asm-mips/txx9/generic.h |   18 ++++++++++++++++++
 3 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/arch/mips/txx9/rbtx4927/irq.c b/arch/mips/txx9/rbtx4927/irq.c
index 22076e3..9c14ebb 100644
--- a/arch/mips/txx9/rbtx4927/irq.c
+++ b/arch/mips/txx9/rbtx4927/irq.c
@@ -133,9 +133,9 @@ static int toshiba_rbtx4927_irq_nested(int sw_irq)
        u8 level3;
level3 = readb(rbtx4927_imstat_addr) & 0x1f;
-       if (level3)
-               sw_irq = RBTX4927_IRQ_IOC + fls(level3) - 1;
-       return sw_irq;
+       if (unlikely(!level3))
+               return -1;
+       return RBTX4927_IRQ_IOC + __fls8(level3);
 }
static void __init toshiba_rbtx4927_irq_ioc_init(void)
diff --git a/arch/mips/txx9/rbtx4938/irq.c b/arch/mips/txx9/rbtx4938/irq.c
index ca2f830..7d21bef 100644
--- a/arch/mips/txx9/rbtx4938/irq.c
+++ b/arch/mips/txx9/rbtx4938/irq.c
@@ -85,10 +85,10 @@ static int toshiba_rbtx4938_irq_nested(int sw_irq)
        u8 level3;
level3 = readb(rbtx4938_imstat_addr);
-       if (level3)
-               /* must use fls so onboard ATA has priority */
-               sw_irq = RBTX4938_IRQ_IOC + fls(level3) - 1;
-       return sw_irq;
+       if (unlikely(!level3))
+               return -1;
+       /* must use fls so onboard ATA has priority */
+       return RBTX4938_IRQ_IOC + __fls8(level3);
 }
static void __init

WBR, Sergei



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