On Mon, Aug 04, 2008 at 05:40:57PM -0600, Paul Walmsley wrote:
>
> Add the MT_MEMORY_STRONGLY_ORDERED memory type for ARM strongly ordered
> memory.
>
> This is used on OMAP3 for on-board SRAM. On OMAP, SRAM is used for code
> that changes the SDRAM controller's clock, temporarily blocking access to
> SDRAM. During this period, as code executes from SRAM, the ARM cache
> controller can attempt to write dirty cache lines back to SDRAM to make
> room for SRAM cache lines, causing the MPU subsystem to hang. To avoid
> this, we mark SRAM as strongly- ordered memory.
Is the controller allowed to write dirty cache lines out at any time it
likes? Surely a better fix is to drain the cache of the changes before
changing the clock for the SDRAM?
> Problem noted by Richard Woodruff <r-woodruff2@xxxxxx>. Fix derived
> from the TI CDP codebase.
>
> Signed-off-by: Paul Walmsley <paul@xxxxxxxxx>
> ---
>
> arch/arm/mm/mmu.c | 5 +++++
> include/asm-arm/mach/map.h | 13 +++++++------
> 2 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 2d6d682..5b56539 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -239,6 +239,11 @@ static struct mem_type mem_types[] = {
> .prot_sect = PMD_TYPE_SECT,
> .domain = DOMAIN_KERNEL,
> },
> + [MT_MEMORY_STRONGLY_ORDERED] = {
> + .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE |
> + PMD_SECT_UNCACHED,
> + .domain = DOMAIN_KERNEL,
> + },
> };
>
> const struct mem_type *get_mem_type(unsigned int type)
> diff --git a/include/asm-arm/mach/map.h b/include/asm-arm/mach/map.h
> index 7ef3c83..8cb46b7 100644
> --- a/include/asm-arm/mach/map.h
> +++ b/include/asm-arm/mach/map.h
> @@ -19,12 +19,13 @@ struct map_desc {
> };
>
> /* types 0-3 are defined in asm/io.h */
> -#define MT_CACHECLEAN 4
> -#define MT_MINICLEAN 5
> -#define MT_LOW_VECTORS 6
> -#define MT_HIGH_VECTORS 7
> -#define MT_MEMORY 8
> -#define MT_ROM 9
> +#define MT_CACHECLEAN 4
> +#define MT_MINICLEAN 5
> +#define MT_LOW_VECTORS 6
> +#define MT_HIGH_VECTORS 7
> +#define MT_MEMORY 8
> +#define MT_ROM 9
> +#define MT_MEMORY_STRONGLY_ORDERED 10
>
> #define MT_NONSHARED_DEVICE MT_DEVICE_NONSHARED
> #define MT_IXP2000_DEVICE MT_DEVICE_IXP2000
>
>
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--
--
Ben
Q: What's a light-year?
A: One-third less calories than a regular year.
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