[PATCH v10 05/11] arm: armv8: mmu: add mem_map_from_dram_banks

[Ilias Apalodimas]

Hi Anshul,

On Fri, 10 Oct 2025 at 16:44, 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_from_dram_banks that
> modifies the static map in a similar way. Allowing the caller to map all
> dram banks by just passing the index to last entry in their mem_map and
> it's length.
>
> Reviewed-by: Dhruva Gole <d-gole at ti.com>
> Signed-off-by: Anshul Dalal <anshuld at ti.com>
> Tested-by: Wadim Egorov <w.egorov at phytec.de>
> ---
>  arch/arm/cpu/armv8/cache_v8.c    | 28 ++++++++++++++++++++++++++++
>  arch/arm/include/asm/armv8/mmu.h | 11 +++++++++++
>  2 files changed, 39 insertions(+)
>
> diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
> index 74c78cb2fb0..9b3c37dae82 100644
> --- a/arch/arm/cpu/armv8/cache_v8.c
> +++ b/arch/arm/cpu/armv8/cache_v8.c
> @@ -58,6 +58,34 @@ static int get_effective_el(void)
>         return el;
>  }
>
> +int mem_map_from_dram_banks(unsigned int index, unsigned int len, u64 attrs)
> +{
> +       unsigned int i;
> +       int ret = fdtdec_setup_memory_banksize();
> +
> +       if (ret) {
> +               log_err("%s: Failed to setup dram banks\n", __func__);
> +               return ret;
> +       }
> +
> +       if (index + CONFIG_NR_DRAM_BANKS >= len) {
> +               log_err("%s: Provided mem_map array has insufficient size for DRAM entries\n",
> +                       __func__);
> +               return -ENOMEM;
> +       }
> +
> +       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++;
> +       }
> +
> +       memset(&mem_map[index], 0, sizeof(mem_map[index]));
> +
> +       return 0;
> +}

Is there a reason we add all the memory maps now and remove them later
with mmu_unmap_reserved_mem(). IOW we could add the DT parsing in this
function and not map the 'no-map' addresses to begin with.
Unless someone changes the DTB on the fly ?

Thanks
/Ilias
>  u64 get_tcr(u64 *pips, u64 *pva_bits)
>  {
>         int el = get_effective_el();
> diff --git a/arch/arm/include/asm/armv8/mmu.h b/arch/arm/include/asm/armv8/mmu.h
> index 3807c702fb6..6e7a3366844 100644
> --- a/arch/arm/include/asm/armv8/mmu.h
> +++ b/arch/arm/include/asm/armv8/mmu.h
> @@ -194,8 +194,19 @@ struct mm_region {
>         u64 attrs;
>  };
>
> +/* Used as the memory map for MMU configuration by mmu_setup */
>  extern struct mm_region *mem_map;
>  void setup_pgtables(void);
> +
> +/**
> + * mem_map_from_dram_banks() - Populate mem_map with entries corresponding to
> + * dram banks as per the gd. This should be called prior to mmu_setup.
> + *
> + * @index: The entry in mem_map to start the over-write
> + * @len: The size of mem_map
> + */
> +int mem_map_from_dram_banks(unsigned int index, unsigned int len, u64 attrs);
> +
>  u64 get_tcr(u64 *pips, u64 *pva_bits);
>
>  /**
> --
> 2.51.0
>