Re: [PATCH 14/23] ARM: i.MX: scratch: add OP-TEE FDTO support

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

Hello Marco,

On 11/10/25 9:34 PM, Marco Felsch wrote:
> OP-TEE has the support to write DTB overlay fragments if enabled via
> OP-TEE config switch CFG_EXTERNAL_DTB_OVERLAY.
> 
> The overlay fragments are added to the exisiting DTB if OP-TEE was
> started with a DTB provided via arg2 or written to a stand-alone DTB
> overlay.
> 
> This adds a dedicated storage slot which can be passed to OP-TEE or be
> used by barebox to extract the added overlay fragment into it.
> 
> Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> ---


> +config SCRATCH_FDTO_SIZE
> +	hex
> +	default 0x0
> +	default 0x4000 if PBL_EARLY_FDT_LOAD
> +	prompt "Scratch FDTO size"
> +	help
> +	  The size of possible FDT overlay areas used by BL3x binaries to store
> +	  runtime generated overlays. Can be 0x0 if early FDT support is not
> +	  requied e.g. during BL31 and BL32 stage.

I understand the need, but I dislike that we add such fine-grained
Kconfig symbols here. With Sascha's series to make barebox proper an
ELF, PBL will have more insight about how much space barebox proper
occupies and I intend to send a series after it to allow easier
allocation for hand-off data.

I will include provisions for passing around the device tree and an
overlay with that series, so please hold off sending your v2 until then.

Thanks,
Ahmad


> +
>  config MALLOC_ALIGNMENT
>  	hex
>  	default 8
> diff --git a/include/mach/imx/scratch.h b/include/mach/imx/scratch.h
> index 43bf55de48099f1662cd4331620a93303d4dd710..a9745a95732dd961dcae83ec46c3eaa078d62a16 100644
> --- a/include/mach/imx/scratch.h
> +++ b/include/mach/imx/scratch.h
> @@ -15,6 +15,7 @@ const struct optee_header *imx_scratch_get_optee_hdr(void);
>  void imx_scratch_save_optee_hdr(const struct optee_header *hdr);
>  
>  void imx_scratch_get_fdt(void **fdt, unsigned int *fdt_sz);
> +void imx_scratch_get_optee_fdto(void **fdto, unsigned int *fdto_sz);
>  
>  #define imx8mq_init_scratch_space() imx8m_init_scratch_space(32, true)
>  #define imx8mm_init_scratch_space() imx8m_init_scratch_space(32, true)
> 

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