On Fri, 17 Oct 2025 at 15:47, Anshul Dalal <[email protected]> wrote: > > 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.
Fair enough. Since you'll send a V11 adding this on the description helps. Also mention that this should all happen before enabling the caches, so mapping memory that is marked as no-map; shouldn't cause any crashes Thanks /Ilias > > Regards, > Anshul
