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Re: [PATCH 1/3] fixed mtc0_tlbw_hazard

To: Sergei Shtylyov <sshtylyov@dev.rtsoft.ru>
Subject: Re: [PATCH 1/3] fixed mtc0_tlbw_hazard
From: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Date: Fri, 22 Sep 2006 01:41:42 +0900
Cc: yoichi_yuasa@tripeaks.co.jp, ralf@linux-mips.org, linux-mips@linux-mips.org
In-reply-to: <4512BC2A.6040003@dev.rtsoft.ru>
Organization: TriPeaks Corporation
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20060922010713.657f2861.yoichi_yuasa@tripeaks.co.jp> <4512BC2A.6040003@dev.rtsoft.ru>
Sender: linux-mips-bounce@linux-mips.org
Hi Sergei,

On Thu, 21 Sep 2006 20:22:02 +0400
Sergei Shtylyov <sshtylyov@dev.rtsoft.ru> wrote:

> 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...

ssnop is a part of dvpe().

> > 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.

previous mtc0_tlbw_hazard() for C used nop.
"b . + 8" is trick for R4000/R4400, see comment in old hazard.h .

Yoichi

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