Hi Simon, Thanks for this.
On Sat, 9 May 2026 at 00:33, Simon Glass <[email protected]> wrote: > > The bcm2712 memory map only covers the first 1 GiB of DRAM, but Pi 5 > models ship with up to 16 GiB. Accesses above 1 GiB fault because the > range is not present in the MMU page tables. > > Allocations above 1 GiB used to be blocked at the lmb layer because > memory above ram_top was reserved as no-overwrite. Commit 0efb6bc3e36d > ("lmb: Reinstate access to memory above ram_top") removed that > reservation, so callers like tftp now route allocations into the > unmapped range and trigger a fault. > > Extend the first DRAM entry to 16 GiB to cover the largest addressable > range for any production Pi 5 model. Smaller models are unaffected > because aarch64 only faults on actual access of unbacked memory, and > no peripheral region lies between 1 GiB and 64 GiB on this SoC > (peripherals start at 0x1000000000). So a couple of questions: 1) Do we need to do this for the Pi4 (bcm2711) too? It's currently at ~4Gb. 2) On the bcm2711 it sits at just under 4gb, initially that was 4Gb-16Mb AFAICT (917a1e9a78fe) and then it was reduced in a followup commit (c44b3f523c48) because of overlap with "device's IO area" 3) why doesn't the rpi5 have the overlap issues? Peter > Fixes: 0efb6bc3e36d ("lmb: Reinstate access to memory above ram_top") > Signed-off-by: Simon Glass <[email protected]> > --- > > arch/arm/mach-bcm283x/init.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mach-bcm283x/init.c b/arch/arm/mach-bcm283x/init.c > index 7a1de22e0ae..3d11c9e5c3b 100644 > --- a/arch/arm/mach-bcm283x/init.c > +++ b/arch/arm/mach-bcm283x/init.c > @@ -69,10 +69,10 @@ static struct mm_region > bcm2711_mem_map[MEM_MAP_MAX_ENTRIES] = { > > static struct mm_region bcm2712_mem_map[MEM_MAP_MAX_ENTRIES] = { > { > - /* First 1GB of DRAM */ > + /* DRAM, up to the 16 GiB maximum supported by Pi 5 models */ > .virt = 0x00000000UL, > .phys = 0x00000000UL, > - .size = 0x40000000UL, > + .size = 0x400000000UL, > .attrs = PTE_BLOCK_MEMTYPE(MT_NORMAL) | > PTE_BLOCK_INNER_SHARE > }, { > --- > base-commit: 3cdd19089f1b1b7cd08530f33ff4708abcfd426c > branch: rpi-us > > -- > 2.43.0 >
