[PATCH 5/5] arm64/efi: adapt to relaxed FDT placement requirements

[Mark Rutland]

On Tue, Mar 03, 2015 at 11:03:50AM +0000, Ard Biesheuvel wrote:
> With the relaxed FDT placement requirements in place, we can change
> the allocation strategy used by the stub to put the FDT image higher
> up in memory. At the same time, reduce the minimal alignment to a
> power of 2 upper bound of the size: this way, we are still guaranteed
> not to cross a 2 MB boundary, but will potentially waste less memory
> doing so.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
>  arch/arm64/include/asm/efi.h            | 9 ++++-----
>  drivers/firmware/efi/libstub/arm-stub.c | 2 +-
>  drivers/firmware/efi/libstub/fdt.c      | 7 ++-----
>  3 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
> index ef572206f1c3..68f7bb2ddad7 100644
> --- a/arch/arm64/include/asm/efi.h
> +++ b/arch/arm64/include/asm/efi.h
> @@ -39,12 +39,11 @@ extern void efi_init(void);
>  /* arch specific definitions used by the stub code */
>  
>  /*
> - * AArch64 requires the DTB to be 8-byte aligned in the first 512MiB from
> - * start of kernel and may not cross a 2MiB boundary. We set alignment to
> - * 2MiB so we know it won't cross a 2MiB boundary.
> + * AArch64 requires the DTB to be 8-byte aligned and not cross a 2MiB boundary.
> + * So align to a power of 2 upper bound of the FDT size.
>   */
> -#define EFI_FDT_ALIGN	SZ_2M   /* used by allocate_new_fdt_and_exit_boot() */
> -#define MAX_FDT_OFFSET	SZ_512M
> +#define EFI_FDT_ALIGN(x)	roundup_pow_of_two(x)
> +#define MAX_FDT_OFFSET		ULONG_MAX
>  
>  #define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
>  
> diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
> index dcae482a9a17..c58c21c22dbe 100644
> --- a/drivers/firmware/efi/libstub/arm-stub.c
> +++ b/drivers/firmware/efi/libstub/arm-stub.c
> @@ -269,7 +269,7 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
>  
>  	new_fdt_addr = fdt_addr;
>  	status = allocate_new_fdt_and_exit_boot(sys_table, handle,
> -				&new_fdt_addr, dram_base + MAX_FDT_OFFSET,
> +				&new_fdt_addr, MAX_FDT_OFFSET,

Do we still need the max_addr parameter and MAX_FDT_OFFSET, or can we
just have allocate_new_fdt_and_exit_boot assume it can allocate anywhere
in the physical address space (or ULONG_MAX if we want to allocate below
4GB whenever we get 32-bit EFI stub support).

Otherwise this looks fine.

Mark.