[U-Boot] [PATCH v2 3/4] image: fdt: copy possible optee nodes to a loaded devicetree

[Patrick DELAUNAY]

Hi Jens and Heiko,

> From: U-Boot <u-boot-bounces at lists.denx.de> On Behalf Of Jens Wiklander
> Sent: mercredi 23 octobre 2019 08:46
> 
> On Tue, Oct 22, 2019 at 09:04:27PM +0200, Heiko Stuebner wrote:
> > From: Heiko Stuebner <heiko.stuebner at theobroma-systems.com>
> >
> > The loading convention for optee or any other tee on arm64 is as bl32
> > parameter to the trusted-firmware. So TF-A gets invoked with the TEE
> > as
> > bl32 and main u-boot as bl33. Once it has done its startup TF-A jumps
> > into the bl32 for the TEE startup, returns to TF-A and then jumps to bl33.
> >
> > All of them get passed a devicetree as parameter and all components
> > often get loaded from a FIT image.
> >
> > OP-TEE will create additional nodes in that devicetree namely a
> > firmware node and possibly multiple reserved-memory nodes.
> >
> > While this devicetree is used in main u-boot, in most cases it won't
> > be the one passed to the actual kernel. Instead most boot commands
> > will load a new devicetree from somewhere like mass storage of the
> > network, so if that happens u-boot should transfer the optee nodes to that new
> devicetree.
> >
> > To make that happen introduce optee_copy_fdt_nodes() called from the
> > dt setup function in image-fdt which after checking for the optee
> > presence in the u-boot dt will make sure a optee node is present in
> > the kernel dt and transfer any reserved-memory regions it can find.
> >
> > Signed-off-by: Heiko Stuebner <heiko.stuebner at theobroma-systems.com>
> > ---
> > changes in v2:
> > - don't create a new optee firmware-node, but instead copy the
> >   compatible+method properties from the old fdt blob.
> >
> >  common/image-fdt.c  |   8 +++
> >  include/tee/optee.h |   9 +++
> >  lib/optee/optee.c   | 132 ++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 149 insertions(+)
> >
> [snip]

On STM32MP1 platform (armv7 with TF-A support), 
we can use BL32 = OP-TEE or spmin provide by TF-A

So we are plan to have the same type of feature but with an inversed logical:

- Op-Tee nodes (firmwares and reserved) are present in kernel device tree
- U-Boot deactivated these nodes when TEE is not present, with the next function called in ft_system_setup:

static void stm32_fdt_disable_optee(void *blob)
{
	int off, node;

	off = fdt_node_offset_by_compatible(blob, -1, "linaro,optee-tz");
	if (off >= 0 && fdtdec_get_is_enabled(blob, off))
		fdt_status_disabled(blob, off);

	/* Disabled "optee at ..." reserved-memory node */
	off = fdt_path_offset(blob, "/reserved-memory/");
	if (off < 0)
		return;
	for (node = fdt_first_subnode(blob, off);
	     node >= 0;
	     node = fdt_next_subnode(blob, node)) {
		if (!strncmp(fdt_get_name(blob, node, NULL), "optee@", 6))
			fdt_status_disabled(blob, node);
	}
}

What is  the better for you ?
1/ Copy the U-Boot op-tee nodes in kernel device tree (where op-tee nodes was present)
or 
2/ Deactivate the op-tee nodes in kernel device tree (where op-tee nodes are present)

The advantage of us is to upstream a Linux Kernel device tree with the correct op-tee nodes...

Regards

> Looks good to me:
> Reviewed-by: Jens Wiklander <jens.wiklander at linaro.org>
> 
> Cheers,
> Jens

Patrick