Re: [PATCH 13/23] ARM: i.MX8M: add support to pass BL3x bl_params

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

Hi,

On 11/10/25 9:34 PM, Marco Felsch wrote:
> Add support to handover the BL32 and BL33 entrypoints via the TF-A
> struct::bl_params in arg0. This eliminates the requirement to share the
> different load addresses between multiple binaries to lower the BSP
> integration effort.
>
> In addition to the entriespoints, this commit also adds the support to
> pass the builtin barebox DTB to OP-TEE if enabled.
>
> Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> ---


> +config ARCH_IMX_ATF_PASS_BL_PARAMS
> +	bool "Pass BL3x bl_params as arg0 to TF-A"
> +	depends on ARCH_IMX_ATF
> +	select ARM_ATF
> +	select ARCH_HAS_EARLY_FDT_SUPPORT
> +	help
> +	  Enable this option if you are using an upstream TF-A that uses
> +	  the struct::bl_params to handover all required BL32 and BL33
> +	  information required to start the BL32 and BL33 image.
> +
> +	  Since upstream TF-A v2.12 all i.MX8M support this feature except for
> +	  the i.MX8MQ.
I think the help text is misleading, because you still need to enable
the PBL_EARLY_FDT_LOAD option for this to actually work.

What you want instead is for the SoC symbols for i.MX8M[MNQ] to select
ARCH_HAS_EARLY_FDT_SUPPORT and then this symbol here would select
PBL_EARLY_FDT_LOAD.

PBL_EARLY_FDT_LOAD itself would lose its prompt, but you probably will
want to keep a

  prompt "Include Early FDT loading support" if COMPILE_TEST

So it has coverage from the static analyzers running for sandbox.

> +	if (!IS_ENABLED(CONFIG_ARCH_IMX_ATF_PASS_BL_PARAMS) || cpu_is_mx8mq()) {

Ok, good thing this is guarded, so I think that answers my questions
regarding the LIBFDT dependency.

> +		ret = pbl_load_fdt(fdt, buf, bufsz);

Did you consider replacing the uncompressed DT in the handoff data if we
already spent the time to decompress it here?

> +		if (!ret) {
> +			unsigned long mem_base = MX8M_DDR_CSD1_BASE_ADDR;
> +			unsigned long mem_sz;
> +
> +			if (cpu_is_mx8mn())
> +				mem_sz = imx8m_ddrc_sdram_size(16);
> +			else
> +				mem_sz = imx8m_ddrc_sdram_size(32);
> +
> +			fdt = buf;
> +			ret = fdt_fixup_mem(fdt, &mem_base, &mem_sz, 1);
> +			if (ret) {
> +				pr_warn("Failed to fixup FDT memory node, continue without\n");
> +				fdt = NULL;
> +			}

Ok, that answers my question about the memory being inaccurate.

Keep in mind that all this runs without MMU enabled, so it will be
slower. A FIXME comment may be apt to alert to this fact.

Thanks,
Ahmad


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