[U-Boot] [U-Boot, v4, 07/11] spl: add support to booting with OP-TEE

[Tom Rini]

On Fri, Feb 02, 2018 at 04:56:57PM +0100, Dr. Philipp Tomsich wrote:
> Bryan,
> 
> > On 2 Feb 2018, at 16:37, Bryan O'Donoghue <bryan.odonoghue at linaro.org> wrote:
> > 
> > 
> > 
> > On 02/02/18 15:02, Dr. Philipp Tomsich wrote:
> >> Where do we stand on this: can we reuse IH_TYPE_TEE, will be use IH_TYPE_OPTEE or will there be a new IH_TYPE_OPTEE_SPL?
> > 
> > I think because you aren't doing anything different with the image type you can reuse IH_TYPE_TEE
> > 
> > This
> > 
> > +#if CONFIG_IS_ENABLED(OPTEE)
> > +	case IH_OS_OP_TEE:
> > +		debug("Jumping to U-Boot via OP-TEE\n");
> > +		spl_optee_entry(NULL, NULL, spl_image->fdt_addr,
> > +				(void *)spl_image.entry_point);
> > +		break;
> > +#endif
> > 
> > could just as easily be this
> > 
> > +#if CONFIG_IS_ENABLED(OPTEE)
> > +	case IH_TYPE_TEE:
> > +		debug("Jumping to U-Boot via OP-TEE\n");
> > +		spl_optee_entry(NULL, NULL, spl_image->fdt_addr,
> > +				(void *)spl_image.entry_point);
> > +		break;
> > +#endif
> > 
> > should be a matter of just replacing the call to mkimage to use
> > 
> > mkimage -A arm -T tee
> > 
> > instead of
> > 
> > mkimage -A arm -T optee
> > 
> > and the suggested change above.. case IH_OS_OP_TEE -> case IH_TYPE_TEE
> 
> Thanks for summarising your suggestion.
> 
> However, my mail was intended to test the waters to see what the consensus was.
> A it appears that none has yet emerged between all the involved parties (including
> our colleagues from TI that had also chimed in on the discussion).
> So for now, I’ll sit back and wait until some sort of consensus (or at least a majority
> for one solution or the other) emerges.
> 
> Personally, I am not happy with having a ‘tee’ and an ‘optee’ both refering to OP-TEE
> and the upstream OP-TEE documentation suggesting that their envisioned boot
> process was to boot through the OP-TEE (i.e. what the ‘tee’ image type does).
> However, with the ‘tee’ image type already being defined, we seem to have already
> backed ourselves into a situation where the naming is non-intuitive. 

Alright, I'm a little confused here.  I guess first, there's a
disconnect in upstream OP-TEE land about how 32bit ARM should be done?
I guess we have three different implemented and upstreamed flows:
- SPL->U-Boot->OP-TEE->U-Boot->Linux
- SPL->U-Boot->OP-TEE->Linux
- SPL->OP-TEE->U-Boot->Linux

And in this last case we have a combined image that is passed from SPL
to OP-TEE.

Since all 3 of these flows are in upstream OP-TEE, we need to support
them all.  The biggest constraint is that we have the first flow already
in and named "tee" (my fault, I should have made sure everyone would use
the same flow).  So we need to have descriptive enough names for the
other flows that we're going to add so that it's clear what's what.  How
about "tee-standalone" for "U-Boot starts OP-TEE, and is done" and
"tee-combo" for "SPL gives OP-TEE an image to deal with".  This could
even in theory I suspect be SPL gives OP-TEE a Linux kernel to boot.
I'm also happy to hear better suffixes but I don't want "tee" and
"optee".  And if we can cover two flows under the same name, that's good
too, we just need to name the last flow "tee-something".  Thanks all!

-- 
Tom
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