Re: [PATCH 20/23] ARM: i.MX8M: Add support to extract OP-TEE provided informations

[Marco Felsch <m.felsch@pengutronix.de>]

On 26-01-16, Marco Felsch wrote:
> Hi Ahmad,
> 
> On 26-01-15, Ahmad Fatoum wrote:
> > Hello,
> > 
> > On 1/15/26 4:19 PM, Marco Felsch wrote:
> > > On 26-01-15, Ahmad Fatoum wrote:
> > >>>> +		pr_warn("Failed to extract OP-TEE FDTO, continue without FDTO\n");
> > >>>> +		/*
> > >>>> +		 * Don't BUG() because the system may have compile-time config
> > >>>> +		 * support
> > >>>> +		 */
> > >>>> +		return;
> > >>>> +	}
> > >>>> +
> > >>>> +	handoff_data_add(HANDOFF_DATA_BL32_DT_OVL, fdto_dst, fdto_size);
> > >>>
> > >>> The overlay isn't used in barebox itself, but only for the Kernel.
> > > 
> > > This is not true. This patchset adds to support to use the overlay
> > > within barebox too. With the patches Fabian provided, it would eliminate
> > > the need for i.MX6(ULL) boards to have this strange initcall which
> > > checks a magic memory location for an overlay to apply it.
> > > >>>
> > >>> You Could just pick up the overlay from the i.MX scratch space in
> > >>> barebox proper and pass it to optee_register_overlay().
> > >>
> > >> Agreed. There seems to be no need to do this in the PBL.
> > > 
> > > The early barebox code checks for HANDOFF_DATA_BL32_DT_OVL and applies
> > > the overlay. Do you suggest that I shall extract the data within barebox
> > > common code rather? I'm not sure if this is even possible.
> > 
> > Isn't this basically what virt_board_driver_init() is doing? Would this
> > not work for your purposes?
> > 
> > I am generally not a friend of putting logic that can equally well be
> > located in barebox proper into the PBL. It's slow, it's code duplication
> > and if we do it, there should be a strong reason why it needs to be in
> > the PBL. There might very well be a reason here that this needs to be
> > absolutely done in the PBL (e.g. I can understand fixing up memory size
> > in PBL, because firmware needs it that early), but I don't yet see it
> > here for application of the overlay.
> 
> I see and you're completely right, if something can be done in barebox
> proper we should do it there. I have to check the
> virt_board_driver_init() and how this approach can be re-used for the
> this common abbroach.

I've checked the virt_board_driver_init() and have to disagree. What I
do here is to extract the overlay-fragments into a overlay-only FDT to
not cause any issues while applying the overlay later on. The
virt_board_driver_init() is applying a builtin overlay-only devicetree.

That beeing said, I wasn't sure if we need to extract the
overlay-fragments before applying the overlay. Applying the FDT provided
by OP-TEE which contains both the complete FDT and the overlay-fragments
should work too, but doesn't feel right. Therefore I went the way of
extract them into a dedicated overlay which can be applied later on
without worries (like the virt_board_driver_init() does).

I could check if applying the completed FDT (incl. the
overlay-fragments9 provided by OP-TEE as of-overlay works too.

IMHO this doesn't feel right, but the appending OP-TEE does doesn't feel
right too.

Regards,
  Marco