linux-kernel - Re: [PATCH v4 05/24] openrisc: head: refactor out tlb flush into it's own function

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Date:   Fri, 24 Feb 2017 10:57:19 +0100
From:   Jonas Bonn <jonas@...thpole.se>
To:     Stafford Horne <shorne@...il.com>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
Cc:     linux@...ck-us.net, openrisc@...ts.librecores.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 05/24] openrisc: head: refactor out tlb flush into it's
 own function

On 02/24/2017 05:32 AM, Stafford Horne wrote:
> From: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
>
> This brings it inline with the other setup oprations done like the cache
> enables _ic_enable and _dc_enable.  Also, this is going to make it
> easier to initialize additional cpu's when smp is introduced.

This patch confuses me.  The TLB flush is moved to a point after MMU's 
are enabled.  The TLB flush should happen before enabling the MMU, 
shouldn't it?

/Jonas

>
> Signed-off-by: Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>
> [shorne@...il.com: Added commit body]
> Signed-off-by: Stafford Horne <shorne@...il.com>
> ---
>   arch/openrisc/kernel/head.S | 38 ++++++++++++++++++++++----------------
>   1 file changed, 22 insertions(+), 16 deletions(-)
>
> diff --git a/arch/openrisc/kernel/head.S b/arch/openrisc/kernel/head.S
> index 63ba2d9..a22f1fc 100644
> --- a/arch/openrisc/kernel/head.S
> +++ b/arch/openrisc/kernel/head.S
> @@ -522,22 +522,8 @@ enable_dc:
>   	 l.nop
>   
>   flush_tlb:
> -	/*
> -	 *  I N V A L I D A T E   T L B   e n t r i e s
> -	 */
> -	LOAD_SYMBOL_2_GPR(r5,SPR_DTLBMR_BASE(0))
> -	LOAD_SYMBOL_2_GPR(r6,SPR_ITLBMR_BASE(0))
> -	l.addi	r7,r0,128 /* Maximum number of sets */
> -1:
> -	l.mtspr	r5,r0,0x0
> -	l.mtspr	r6,r0,0x0
> -
> -	l.addi	r5,r5,1
> -	l.addi	r6,r6,1
> -	l.sfeq	r7,r0
> -	l.bnf	1b
> -	 l.addi	r7,r7,-1
> -
> +	l.jal	_flush_tlb
> +	 l.nop
>   
>   /* The MMU needs to be enabled before or32_early_setup is called */
>   
> @@ -629,6 +615,26 @@ jump_start_kernel:
>   	l.jr    r30
>   	 l.nop
>   
> +_flush_tlb:
> +	/*
> +	 *  I N V A L I D A T E   T L B   e n t r i e s
> +	 */
> +	LOAD_SYMBOL_2_GPR(r5,SPR_DTLBMR_BASE(0))
> +	LOAD_SYMBOL_2_GPR(r6,SPR_ITLBMR_BASE(0))
> +	l.addi	r7,r0,128 /* Maximum number of sets */
> +1:
> +	l.mtspr	r5,r0,0x0
> +	l.mtspr	r6,r0,0x0
> +
> +	l.addi	r5,r5,1
> +	l.addi	r6,r6,1
> +	l.sfeq	r7,r0
> +	l.bnf	1b
> +	 l.addi	r7,r7,-1
> +
> +	l.jr	r9
> +	 l.nop
> +
>   /* ========================================[ cache ]=== */
>   
>   	/* aligment here so we don't change memory offsets with