[U-Boot] memcpy/memset on arm64 platforms

[Lokesh Vutla]

Hi All,
	I am trying to enable CONFIG_USE_ARCH_MEMSET/MEMCPY on arm64 platforms and 
realized that there is no arm64 specific memcpy available in u-boot. So I tried 
porting arm64 specific memcpy from kernel[1]. Memcpy stopped working after that 
and observed that if destination address is unaligned then system hangs.

After doing a bit more research, understood  that unaligned access to device or 
strongly ordered memories will fail. And the memory system (even normal RAM) 
behaves like strongly ordered memory when the MMU is disabled[2]. In u-boot MMU 
is enabled very late after relocation and SPL doesn't enable MMU at all.

Before I proceed any further wanted to hear from others if anyone have already 
tried and have any working solution. If not should we update the kernel memcpy 
to use unaligned destination address and use it in u-boot?

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/lib/memcpy.S
[2] 
https://community.arm.com/processors/f/discussions/7557/when-and-where-will-the-ldp-instruction-trigger-an-exception

Thanks and regards,
Lokesh