On 1/11/19 5:13 PM, Tom Rini wrote: > On Mon, Jan 07, 2019 at 02:43:05PM +0530, Lokesh Vutla wrote: > >> 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.
Why do you want a custom memcpy() implementation in the first place ? >> 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. The ARM64 MMU table setup seems to be a mess, it could indeed use some improvement. >> 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 > > I suspect we should, yes. Adding in some custodians of other arm64 > platforms for comment. Does the unaligned access exception happen only before the MMU is enabled or even after ? -- Best regards, Marek Vasut _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
