[U-Boot] [PATCH v5 09/16] arm: Add control over cachability of memory regions

[R Sricharan]

Hi,

> Add support for adjusting the cachability of an L1 section by updating
> the MMU. The mmu_set_region_dcache() function allows drivers to make
> these changes after the MMU is set up.
>
> It is implemented only for ARMv7 at present.
>
> This is needed for LCD support, where we want to make the LCD frame buffer
> write-through (or off) rather than write-back.
>
   This is a much needed support. I was looking for a way to change
   the permissions to avoid speculative aborts for non executable
   regions. This should help.
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
> Changes in v4:
> - Use system bit values for enum dcache_option instead of arbitrary numbers
>
>   arch/arm/cpu/armv7/cache_v7.c |   11 +++++++++
>   arch/arm/include/asm/system.h |   30 ++++++++++++++++++++++++
>   arch/arm/lib/cache-cp15.c     |   50 ++++++++++++++++++++++++++++++++---------
>   3 files changed, 80 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/cpu/armv7/cache_v7.c b/arch/arm/cpu/armv7/cache_v7.c
> index 1b4e808..5f6d039 100644
> --- a/arch/arm/cpu/armv7/cache_v7.c
> +++ b/arch/arm/cpu/armv7/cache_v7.c
> @@ -297,6 +297,12 @@ void arm_init_before_mmu(void)
>   	v7_inval_tlb();
>   }
>
> +void mmu_page_table_flush(unsigned long start, unsigned long stop)
> +{
> +	flush_dcache_range(start, stop);
> +	v7_inval_tlb();
> +}
> +
>   /*
>    * Flush range from all levels of d-cache/unified-cache used:
>    * Affects the range [start, start + size - 1]
> @@ -329,6 +335,11 @@ void arm_init_before_mmu(void)
>   void  flush_cache(unsigned long start, unsigned long size)
>   {
>   }
> +
> +void mmu_page_table_flush(unsigned long start, unsigned long stop)
> +{
> +}
> +
>   #endif /* #ifndef CONFIG_SYS_DCACHE_OFF */
>
>   #ifndef CONFIG_SYS_ICACHE_OFF
> diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
> index 2b28a26..9a05211 100644
> --- a/arch/arm/include/asm/system.h
> +++ b/arch/arm/include/asm/system.h
> @@ -75,6 +75,36 @@ static inline void set_cr(unsigned int val)
>   	isb();
>   }
>
> +/* options available for data cache on each page */
> +enum dcache_option {
> +	DCACHE_OFF = 0x12,
> +	DCACHE_WRITETHROUGH = 0x1a,
> +	DCACHE_WRITEBACK = 0x1e,
> +};
> +
> +/* Size of an MMU section */
> +enum {
> +	MMU_SECTION_SHIFT	= 20,
> +	MMU_SECTION_SIZE	= 1 << MMU_SECTION_SHIFT,
> +};
> +
> +/**
> + * Change the cache settings for a region.
> + *
> + * \param start		start address of memory region to change
> + * \param size		size of memory region to change
> + * \param option	dcache option to select
> + */
> +void mmu_set_region_dcache(u32 start, int size, enum dcache_option option);
> +
> +/**
> + * Register an update to the page tables, and flush the TLB
> + *
> + * \param start		start address of update in page table
> + * \param stop		stop address of update in page table
> + */
> +void mmu_page_table_flush(unsigned long start, unsigned long stop);
> +
>   #endif /* __ASSEMBLY__ */
>
>   #define arch_align_stack(x) (x)
> diff --git a/arch/arm/lib/cache-cp15.c b/arch/arm/lib/cache-cp15.c
> index 939de10..c9bee42 100644
> --- a/arch/arm/lib/cache-cp15.c
> +++ b/arch/arm/lib/cache-cp15.c
> @@ -26,12 +26,6 @@
>
>   #if !(defined(CONFIG_SYS_ICACHE_OFF) && defined(CONFIG_SYS_DCACHE_OFF))
>
> -#if defined(CONFIG_SYS_ARM_CACHE_WRITETHROUGH)
> -#define CACHE_SETUP	0x1a
> -#else
> -#define CACHE_SETUP	0x1e
> -#endif
> -
>   DECLARE_GLOBAL_DATA_PTR;
>
>   void __arm_init_before_mmu(void)
> @@ -50,9 +44,40 @@ static void cp_delay (void)
>   	asm volatile("" : : : "memory");
>   }
>
> -static inline void dram_bank_mmu_setup(int bank)
> +void set_section_dcache(int section, enum dcache_option option)
>   {
>   	u32 *page_table = (u32 *)gd->tlb_addr;
> +	u32 value;
> +
> +	value = (section << MMU_SECTION_SHIFT) | (3 << 10);
   Nit.. How about avoiding this magic value (3 << 10).

> +	value |= option;
> +	page_table[section] = value;
> +}
> +
> +void __mmu_page_table_flush(unsigned long start, unsigned long stop)
> +{
> +	debug("%s: Warning: not implemented\n", __func__);
> +}
> +
> +void mmu_page_table_flush(unsigned long start, unsigned long stop)
> +	__attribute__((weak, alias("__mmu_page_table_flush")));
> +
> +void mmu_set_region_dcache(u32 start, int size, enum dcache_option option)
> +{
> +	u32 *page_table = (u32 *)gd->tlb_addr;
> +	u32 upto, end;
> +
> +	end = ALIGN(start + size, MMU_SECTION_SIZE) >> MMU_SECTION_SHIFT;
> +	start = start >> MMU_SECTION_SHIFT;
> +	debug("mmu_set_region_dcache start=%x, size=%x, option=%d\n",
> +	      start, size, option);
> +	for (upto = start; upto < end; upto++)
> +		set_section_dcache(upto, option);
> +	mmu_page_table_flush((u32)&page_table[start], (u32)&page_table[end]);
> +}
      Should this be page_table[end + 1] instead, to ensure that the
      last entry is also flushed ?