Hello Ilias, On Fri Oct 17, 2025 at 5:39 PM IST, Ilias Apalodimas wrote: > Hi Anshul, > > On Fri, 10 Oct 2025 at 16:44, Anshul Dalal <[email protected]> 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 <[email protected]> >> Signed-off-by: Anshul Dalal <[email protected]> >> Tested-by: Wadim Egorov <[email protected]> >> --- >> 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 ? >
There are two reasons for doing it this way: 1. Modifying mem_map directly makes creating multiple carveouts quite complex with the logic for handling all the edge cases, for example see v4[1] of this series. It's much simpler to use the MMU APIs instead after calling mmu_setup with everything mapped in mem_map. 2. We can't blindly unmap all 'no-map' regions since some regions that would be 'no-map' in the kernel's context are required at U-Boot, like the memory pools for remote cores that rely on U-Boot to load their firmware. Regards, Anshul
