[PATCH -next v6 05/10] arm: armv8: mmu: add mem_map_fix_dram_banks

[Ilias Apalodimas]

Hi Anshul,

On Fri, 5 Sept 2025 at 11:19, Anshul Dalal <anshuld at ti.com> wrote:
>
> For armv8, U-Boot uses a static map defined as 'mem_map' for configuring
> the MMU as part of mmu_setup.
>
> But since the exact configuration of memory banks might not be known at
> build time, many platforms such as imx9, versal2 etc. utilize
> gd->bd->bi_dram to configure the static map at runtime.
>
> Therefore this patch adds a new API mem_map_fix_dram_banks that modifies
> the static map in a similar way. Allowing for anyone to map all dram
> banks by just passing the index to last entry in their mem_map and it's
> length.
>
> Signed-off-by: Anshul Dalal <anshuld at ti.com>
> ---
>  arch/arm/cpu/armv8/cache_v8.c    | 27 +++++++++++++++++++++++++++
>  arch/arm/include/asm/armv8/mmu.h | 10 ++++++++++
>  2 files changed, 37 insertions(+)
>
> diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
> index 6e662395a83..edb895da1f2 100644
> --- a/arch/arm/cpu/armv8/cache_v8.c
> +++ b/arch/arm/cpu/armv8/cache_v8.c
> @@ -58,6 +58,33 @@ static int get_effective_el(void)
>         return el;
>  }
>
> +int mem_map_fix_dram_banks(unsigned int index, unsigned int len, u64 attrs)
> +{
> +       unsigned int i;
> +       int ret = fdtdec_setup_memory_banksize();
> +
> +       if (ret) {
> +               printf("%s: Failed to setup dram banks\n", __func__);
> +               return ret;
> +       }
> +
> +       if (index + CONFIG_NR_DRAM_BANKS >= len) {
> +               printf("%s: Not sufficient space in memory map\n", __func__);
> +               return -ENOMEM;
> +       }

The length of the mem_map array is configured at compile time.
So this is going to fail for all existing boards unless someone
explicitly changes the size of their struct mm_region.
I think if we go down that path, we need to change the error message
as well and point them to the right direction

> +
> +       for (i = 0; i < CONFIG_NR_DRAM_BANKS; i++) {
> +               mem_map[index].virt = gd->bd->bi_dram[i].start;
> +               mem_map[index].phys = gd->bd->bi_dram[i].start;
> +               mem_map[index].size = gd->bd->bi_dram[i].size;
> +               mem_map[index].attrs = attrs;
> +               index++;
> +       }
> +
> +       mem_map[index] = (const struct mm_region){ 0 };

Why do you need the const?
Can we do
memset(&mem_map[index], 0, sizeof(mem_map[index]));
instead?

[...]

Thanks
/Ilias