[PATCH v2 0/4] Relocate U-Boot in the last bank

[Ilias Apalodimas]

Hi,
This is v2 of [1]

There was a discussion recently on the mailing lists regarding our
management of memory above ram_top [0]. The tl;dr is that we have two problems.

The first one is that U-Boot always relocates to the top of the first available
bank unless there's special board code to sidestep that. The second is we don't
successfully deal with devices that can only do 32-bit DMA.

This patch series deals with the first problem by adding a Kconfig option
allowing platforms to relocate to the top of the last discovered bank.

It's worth noting that this is easily testable with QEMU

qemu-system-aarch64 -m 8192 -smp 2 -nographic -cpu cortex-a57 \
    -machine virt,secure=off \
    -bios u-boot.bin \
    -device virtio-rng-pci \
    -drive id=os,if=none,file="$image" \
    -device virtio-blk-device,drive=os \
    -object memory-backend-ram,id=ram0,size=4G \
    -object memory-backend-ram,id=ram1,size=4G \
    -numa node,memdev=ram0 \
    -numa node,memdev=ram1

# RELOCATE_LAST_BANK not set
Hit any key to stop autoboot: 0
=> bdinfo
[...]
relocaddr   = 0x000000013f66c000
reloc off   = 0x000000013f66c000
[...]
lmb_dump_all:
 memory.count = 0x1
 memory[0]	[0x40000000-0x23fffffff], 0x200000000 bytes, flags: none
 reserved.count = 0x2
 reserved[0]	[0x13d507000-0x13d509fff], 0x3000 bytes, flags: no-notify, no-overwrite
 reserved[1]	[0x13d50aff0-0x23fffffff], 0x102af5010 bytes, flags: no-overwrite
devicetree  = board
[...]
TLB addr    = 0x000000013ffe0000
irq_sp      = 0x000000013e50aff0
sp start    = 0x000000013e50aff0
Early malloc usage: e88 / 2000
=>

# RELOCATE_LAST_BANK enabled

=> bdinfo
[...]
relocaddr   = 0x000000023f66c000
reloc off   = 0x000000023f66c000
[...]
lmb_dump_all:
 memory.count = 0x1
 memory[0]	[0x40000000-0x23fffffff], 0x200000000 bytes, flags: none
 reserved.count = 0x2
 reserved[0]	[0x23d507000-0x23d509fff], 0x3000 bytes, flags: no-notify, no-overwrite
 reserved[1]	[0x23d50aff0-0x23fffffff], 0x2af5010 bytes, flags: no-overwrite
devicetree  = board
[...]
TLB addr    = 0x000000023ffe0000
irq_sp      = 0x000000023e50aff0
sp start    = 0x000000023e50aff0
Early malloc usage: e88 / 2000
=>

[1] https://lore.kernel.org/u-boot/20260326115111.1631261-1-ilias.apalodimas@linaro.org/

Changes since v1:
- Adjusted the commit message of patch #4 and explain potential
  breakages
- ram_size recalculation is now split in its own function
- Slighly better description of the Kconfig option
- error checking on fdtdec_setup_mem_ram_top()

Ilias Apalodimas (2):
  fdtdec: Introduce fdtdec_setup_ram_size() to determine the memory size
  common: Allow relocations on the top of the last bank

Marek Vasut (2):
  fdtdec: Deduplicate iterator function
  fdtdec: Introduce fdtdec_setup_mem_ram_top() to determine end of
    topmost DRAM bank

 Kconfig          |   7 ++++
 common/board_f.c |  15 +++++++
 include/fdtdec.h |  31 ++++++++++++++
 lib/fdtdec.c     | 105 ++++++++++++++++++++++++++++-------------------
 4 files changed, 115 insertions(+), 43 deletions(-)

--
2.53.0