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Date:	Thu, 21 Sep 2006 20:22:02 +0400
From:	Sergei Shtylyov <sshtylyov@dev.rtsoft.ru>
Organization: RTSoft, Inc.
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To:	Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
CC:	Ralf Baechle <ralf@linux-mips.org>,
	linux-mips <linux-mips@linux-mips.org>
Subject: Re: [PATCH 1/3] fixed mtc0_tlbw_hazard
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