Re: [PATCH 3/3] ARM: rockchip: pack the device tree passed to TF-A and OP-TEE

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Sascha,

On 10/1/26 9:42 AM, Sascha Hauer wrote:
> rockchip_create_optee_fdt() builds a device tree with just the memory
> nodes, but fdt_create_empty_tree() sets its totalsize to the size of the
> whole scratch buffer, i.e. CONFIG_ARCH_ROCKCHIP_ATF_FDT_SIZE (384 KiB).
> 
> TF-A and OP-TEE both call fdt_open_into() on the device tree, which
> copies totalsize bytes regardless of the actual content. TF-A does this
> with the MMU disabled and OP-TEE through an uncached mapping. On an
> RK3588 this takes 185 ms in TF-A and another 182 ms in OP-TEE.
> 
> Pack the device tree so that totalsize matches its content. OP-TEE can
> still expand it in place, the scratch buffer keeps its size.

While I don't object to the patch, for future reference it would be good
to point out what the implication is for fixups onto the device tree.

Do both TF-A and OP-TEE apply fixups on this platforms? Are these fixups
no longer possible now?

Thanks,
Ahmad

> 
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  arch/arm/mach-rockchip/atf.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/mach-rockchip/atf.c b/arch/arm/mach-rockchip/atf.c
> index e1ca197430..4b88de8317 100644
> --- a/arch/arm/mach-rockchip/atf.c
> +++ b/arch/arm/mach-rockchip/atf.c
> @@ -172,7 +172,7 @@ static int rockchip_create_optee_fdt(void *buf, int bufsize)
>  {
>  	unsigned long base[ROCKCHIP_MAX_DRAM_RESOURCES];
>  	unsigned long size[ARRAY_SIZE(base)];
> -	int i, root;
> +	int i, root, ret;
>  
>  	if (fdt_create_empty_tree(buf, bufsize) != 0)
>  		return -EINVAL;
> @@ -187,7 +187,12 @@ static int rockchip_create_optee_fdt(void *buf, int bufsize)
>  		size[i] = memsize[i];
>  	}
>  
> -	return fdt_fixup_mem(buf, base, size, n_mem_resources);
> +	ret = fdt_fixup_mem(buf, base, size, n_mem_resources);
> +	if (ret)
> +		return ret;
> +
> +	/* TF-A and OP-TEE copy the whole totalsize, keep it small */
> +	return fdt_pack(buf);
>  }
>  
>  static void rockchip_atf_load_bl31(void *fdt)
> 

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