[PATCH 08/10] arm64: dts: Make sure that all DTBs are 64bit aligned for 64bit systems

[Andre Przywara]

On 8/19/21 12:19 PM, Michal Simek wrote:

Hi Michal,

> DTBs for 64bit systems should be also 64bit aligned.

What does "align" mean here, exactly? This is about generating .dtb 
*files*, right? dtc makes sure that the internal structures are properly 
aligned, so what else should be aligned here?

> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
> ---
> 
>   arch/arm/dts/Makefile | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
> index 537c96bf5b35..8d4fc333ea7a 100644
> --- a/arch/arm/dts/Makefile
> +++ b/arch/arm/dts/Makefile
> @@ -1,5 +1,9 @@
>   # SPDX-License-Identifier: GPL-2.0+
>   
> +ifdef CONFIG_PHYS_64BIT
> +DTC_FLAGS += -a 0x8

By looking into the dtc source this looks like to make sure the *size* 
of the DTB is 8-byte aligned, is that the intention here, or even 
useful? If it is, it should apply unconditionally, not only to 64-bit 
systems.

Cheers,
Andre

> +endif
> +
>   dtb-$(CONFIG_TARGET_SMARTWEB) += at91sam9260-smartweb.dtb
>   dtb-$(CONFIG_TARGET_TAURUS) += at91sam9g20-taurus.dtb
>   dtb-$(CONFIG_TARGET_CORVUS) += at91sam9g45-corvus.dtb
>