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SubjectRe: [RFC 1/3] arm: mm: reordering memory type table
On Mon, Sep 10, 2018 at 05:50:11PM +0100, Catalin Marinas wrote:
> On Thu, Sep 06, 2018 at 07:22:10PM +0900, Minchan Kim wrote:
> > diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h
> > index 92fd2c8a9af0..91b99fadcba1 100644
> > --- a/arch/arm/include/asm/pgtable-2level.h
> > +++ b/arch/arm/include/asm/pgtable-2level.h
> > @@ -164,14 +164,23 @@
> > #define L_PTE_MT_BUFFERABLE (_AT(pteval_t, 0x01) << 2) /* 0001 */
> > #define L_PTE_MT_WRITETHROUGH (_AT(pteval_t, 0x02) << 2) /* 0010 */
> > #define L_PTE_MT_WRITEBACK (_AT(pteval_t, 0x03) << 2) /* 0011 */
> > +#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */
> > #define L_PTE_MT_MINICACHE (_AT(pteval_t, 0x06) << 2) /* 0110 (sa1100, xscale) */
> > #define L_PTE_MT_WRITEALLOC (_AT(pteval_t, 0x07) << 2) /* 0111 */
> > -#define L_PTE_MT_DEV_SHARED (_AT(pteval_t, 0x04) << 2) /* 0100 */
> > -#define L_PTE_MT_DEV_NONSHARED (_AT(pteval_t, 0x0c) << 2) /* 1100 */
> > +#if defined(CONFIG_CPU_V7) || defined(CONFIG_CPU_V7M) || \
> > + defined (CONFIG_CPU_V6) || defined(CONFIG_CPU_V6K)
> > +#define L_PTE_MT_DEV_WC L_PTE_MT_BUFFERABLE
> > +#define L_PTE_MT_DEV_CACHED L_PTE_MT_WRITEBACK
> > +#define L_PTE_MT_DEV_NONSHARED L_PTE_MT_MINICACHE
>
> I think you can just ignore v7M here, it doesn't have an MMU.

I didn't know that. Will fix.

>
> You are defining L_PTE_MT_DEV_NONSHARED to L_PTE_MT_MINICACHE but what I
> think you just meant is index 6 in the cpu_v6_mt_table which I would use
> explicitly to avoid confusion.
>
> Anyway, on ARMv7 or ARMv6+LPAE, the non-shared device gets mapped to
> shared device in hardware. Looking through the arm32 code, it seems that

Thanks for the information. I didn't know that.

> MT_DEVICE_NONSHARED is used by arch/arm/mach-shmobile/setup-r8a7779.c
> and IIUC that's a v7 platform (R-Car H1, Cortex-A9). I think the above
> should be defined to L_PTE_MT_DEV_SHARED, unless I miss any place where
> DEV_NONSHARED is relevant on ARMv6 (adding Simon to confirm on
> shmobile).

Simon, could you confirm this?

>
> > diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> > index 81d0efb055c6..f896a30653fa 100644
> > --- a/arch/arm/mm/proc-macros.S
> > +++ b/arch/arm/mm/proc-macros.S
> > @@ -134,21 +134,21 @@
> > .macro armv6_mt_table pfx
> > \pfx\()_mt_table:
>
> Since you changed the MT index, you'd have to fix proc-v7-*levels.S as
> well. If you define DEV_NONSHARED to SHARED, I think you only need to
> update the index for L_PTE_MT_VECTORS.

Good idea. I will try it on.

Thanks for the review, Catalin.

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