Hi Udit,
On 4/25/25 12:35, Kumar, Udit wrote:
> On 4/25/2025 11:09 AM, Ahmad Fatoum wrote:
>> Thinking about it, I am wondering whether U-Boot go is inherently broken,
>> even for the jump-table use case, if caches are enabled:
>
> Correct, this is what I think . Before jumping to new program go command
> should make sure
>
> things are in correct order by cache flush. Kind of below
>
> diff --git a/cmd/boot.c b/cmd/boot.c
> index 23496cafdf5..e6bb1d94a1c 100644
> --- a/cmd/boot.c
> +++ b/cmd/boot.c
> @@ -18,6 +18,7 @@ __attribute__((weak))
> unsigned long do_go_exec(ulong (*entry)(int, char * const []), int argc,
> char *const argv[])
> {
> + flush_cache(...)
yes, even with MMU left enabled, it looks like there should be an
I-Cache invalidate and D-Cache flush/clean here[1].
> I see even ARM64, few board choose to over-ride default option (board/
> xilinx/versal/board.c)
>
> do_go_exec does dcache_disable()
I think __weak is a fundamental mistake and upstream boards abusing it
to not have to fix things generally shows that.
> Sorry I was not clear in previous message,
>
> Here OS take care of caching , irrespective of how boot is done through fit
Yes, but with the assumption that MMU was disabled at start.
> or kind of efi or other method.
Interestingly, with EFI MMU should be left enabled. Linux even
warns about the case that MMU was disabled when entering the stub.
Cheers,
Ahmad
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