linux-kernel - Re: [PATCH v2] powerpc 8xx: Fixing issue with CONFIG_PIN

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Date:	Thu, 12 Sep 2013 13:44:29 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Christophe Leroy <christophe.leroy@....fr>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>,
	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
Subject: Re: [PATCH v2] powerpc 8xx: Fixing issue with CONFIG_PIN_TLB

On Thu, 2013-09-12 at 20:25 +0200, Christophe Leroy wrote:
> This is a reorganisation of the setup of the TLB at kernel startup, in order
> to handle the CONFIG_PIN_TLB case in accordance with chapter 8.10.3 of MPC866
> and MPC885 reference manuals.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> 
> diff -ur linux-3.11.org/arch/powerpc/kernel/head_8xx.S linux-3.11/arch/powerpc/kernel/head_8xx.S
> --- linux-3.11.org/arch/powerpc/kernel/head_8xx.S	2013-09-02 22:46:10.000000000 +0200
> +++ linux-3.11/arch/powerpc/kernel/head_8xx.S	2013-09-09 11:28:54.000000000 +0200
> @@ -785,27 +785,24 @@
>   * these mappings is mapped by page tables.
>   */
>  initial_mmu:
> -	tlbia			/* Invalidate all TLB entries */
> -/* Always pin the first 8 MB ITLB to prevent ITLB
> -   misses while mucking around with SRR0/SRR1 in asm
> -*/
> -	lis	r8, MI_RSV4I@h
> -	ori	r8, r8, 0x1c00
> -
> +	lis	r8, MI_RESETVAL@h
>  	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */
>  
> -#ifdef CONFIG_PIN_TLB
> -	lis	r10, (MD_RSV4I | MD_RESETVAL)@h
> -	ori	r10, r10, 0x1c00
> -	mr	r8, r10
> -#else
>  	lis	r10, MD_RESETVAL@h
> -#endif
>  #ifndef CONFIG_8xx_COPYBACK
>  	oris	r10, r10, MD_WTDEF@h
>  #endif
>  	mtspr	SPRN_MD_CTR, r10	/* Set data TLB control */
>  
> +	tlbia			/* Invalidate all TLB entries */

Is this change to make sure we invalidate everything even if the
bootloader set RSV4I?

> +	ori	r8, r8, 0x1c00
> +	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */
> +#ifdef CONFIG_PIN_TLB
> +	ori	r10, r10, 0x1c00
> +	mtspr	SPRN_MD_CTR, r10	/* Set data TLB control */
> +#endif

Still 0x1c00?

>  	/* Now map the lower 8 Meg into the TLBs.  For this quick hack,
>  	 * we can load the instruction and data TLB registers with the
>  	 * same values.
> @@ -825,6 +822,12 @@
>  	mtspr	SPRN_MI_AP, r8
>  	mtspr	SPRN_MD_AP, r8
>  
> +	/* Always pin the first 8 MB ITLB to prevent ITLB
> +	 * misses while mucking around with SRR0/SRR1 in asm
> +	 */
> +	lis	r8, (MI_RSV4I | MI_RESETVAL)@h
> +	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */

Entry 0 is not pinnable.

-Scott



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