Usually ARMv8 platforms allow unaligned access for Normal memory. But some chips might not allow it by default, having SCTLR.A bit set to 1 before U-Boot execution. One such example is Exynos850 SoC. As allow_unaligned() is not implemented for ARMv8 at the moment, its __weak implementation is used, which does nothing. That might lead to unaligned access abort, for example when running EFI selftest. Fix that by implementing allow_unaligned() for ARMv8.
The issue was found when running EFI selftest on E850-96 board (Exynos850 based):
=> bootefi selftest $fdtcontroladdr
... Executing 'HII database protocols' "Synchronous Abort" handler, esr 0x96000021, far 0xbaac0991 ... resetting ...
Unaligned abort happens in u16_strnlen(), which is called from efi_hii_sibt_string_ucs2_block_next():
u16_strlen(blk->string_text)
where 'blk' type is struct efi_hii_sibt_string_ucs2_block. Because this struct is packed, doing "->string_text" makes 'blk' address incremented by 1 byte, which makes it unaligned. Although allow_unaligned() was called in efi_init_early() before EFI selftest execution, it wasn't implemented for ARMv8 CPUs, so data abort happened.
Signed-off-by: Sam Protsenko semen.protsenko@linaro.org --- arch/arm/cpu/armv8/cpu.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/arch/arm/cpu/armv8/cpu.c b/arch/arm/cpu/armv8/cpu.c index d568efa427ab..82ecf02f4b03 100644 --- a/arch/arm/cpu/armv8/cpu.c +++ b/arch/arm/cpu/armv8/cpu.c @@ -94,3 +94,8 @@ void armv8_setup_psci(void) secure_ram_addr(psci_arch_init)(); } #endif + +void allow_unaligned(void) +{ + set_sctlr(get_sctlr() & ~CR_A); +}