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Re: [PATCH 1/3] fixed mtc0_tlbw_hazard

To: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Subject: Re: [PATCH 1/3] fixed mtc0_tlbw_hazard
From: Sergei Shtylyov <sshtylyov@dev.rtsoft.ru>
Date: Thu, 21 Sep 2006 20:22:02 +0400
Cc: Ralf Baechle <ralf@linux-mips.org>, linux-mips <linux-mips@linux-mips.org>
In-reply-to: <20060922010713.657f2861.yoichi_yuasa@tripeaks.co.jp>
Organization: RTSoft, Inc.
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20060922010713.657f2861.yoichi_yuasa@tripeaks.co.jp>
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Hello.

Yoichi Yuasa wrote:

Some mtc0_tlbw_hazard() were broken by "[MIPS] Cleanup hazard handling" patch.
Please apply this patch.

tlb-r4k.o disassemble:

8009018c <local_flush_tlb_all>:
8009018c:       40066000        mfc0    a2,$12
80090190:       34c1001f        ori     at,a2,0x1f
80090194:       3821001f        xori    at,at,0x1f
80090198:       40816000        mtc0    at,$12
8009019c:       00000040        ssnop
800901a0:       00000040        ssnop
800901a4:       00000040        ssnop

   Hm, why there are ssnop's here...

800901a8:       40075000        mfc0    a3,$10
800901ac:       40801000        mtc0    zero,$2
800901b0:       40801800        mtc0    zero,$3
800901b4:       40043000        mfc0    a0,$6
800901b8:       3c028035        lui     v0,0x8035
800901bc:       8c457ac0        lw      a1,31424(v0)
800901c0:       0085182a        slt     v1,a0,a1
800901c4:       1060000b        beqz    v1,800901f4 <local_flush_tlb_all+0x68>
800901c8:       00044340        sll     t0,a0,0xd
800901cc:       3c098000        lui     t1,0x8000
800901d0:       01091821        addu    v1,t0,t1
800901d4:       40835000        mtc0    v1,$10
800901d8:       10000002        b       800901e4 <local_flush_tlb_all+0x58> <-- 
mtc0_tlbw_hazard()
800901dc:       40840000        mtc0    a0,$0
800901e0:       42000002        tlbwi

Yoichi

Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>

diff -pruN -X mips/Documentation/dontdiff mips-orig/include/asm-mips/hazards.h 
mips/include/asm-mips/hazards.h
--- mips-orig/include/asm-mips/hazards.h        2006-09-21 18:21:11.793973750 
+0900
+++ mips/include/asm-mips/hazards.h     2006-09-21 18:55:07.569201750 +0900
@@ -138,7 +138,7 @@ ASMMACRO(back_to_back_c0_hazard,
  * Mostly like R4000 for historic reasons
  */
 ASMMACRO(mtc0_tlbw_hazard,
-        b      . + 8
+        nop; nop; nop; nop; nop; nop

   ... and nop's there? This looks inconsistent.

        )
 ASMMACRO(tlbw_use_hazard,
         nop; nop; nop; nop; nop; nop
@@ -169,7 +169,7 @@ ASMMACRO(back_to_back_c0_hazard,
  * processors.
  */
 ASMMACRO(mtc0_tlbw_hazard,
-        b      . + 8
+        nop; nop; nop; nop; nop; nop
        )
 ASMMACRO(tlbw_use_hazard,
         nop; nop; nop; nop; nop; nop

WBR, Sergei

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