[U-Boot] u-boot on raspberry 2: booting in SVC secure mode

[Stephen Warren <swarren@wwwdotorg.org>]

On 02/25/2015 02:30 AM, Vincent wrote:
> Hi,
> as explained here http://community.arm.com/message/25127, it is possible to
> boot the raspberry 2 in secure mode, by adding the kernel_old=1 option in
> config.txt. The main effects of this option are:
> - all 4 cores start executing in secure SVC mode instead of non-secure SVC
> mode
> - all 4 cores start at 0x0000 instead of 0x8000
> - the initial boot code that setup SMP and exits secure mode is not
> executed
>
> After browsing u-boot's source code, it seems that their boot code is more
> or less extracted from what u-boot is doing. However I didn't manage to
> compile u-boot for the raspberry 2 supporting this secure mode.
>
> Could anyone explain me what options I need to configure in rpi_2_defconfig
> so that u-boot supports secure boot for the raspberry 2 and what the boot
> sequence will be in this case ? I don't mind fixing the code if necessary
> but I'm a bit lost in the order of events in the initialization.

(Luckily I just happened to notice this message while looking at another 
one nearby. CCing the relevant board maintainer(s) explicitly would help 
your messages be noticed)

To modify U-Boot to support the alternate entry point/load address, 
you'd hopefully only need to change the definition of 
CONFIG_SYS_TEXT_BASE in include/configs/rpi*.h.

I wasn't aware of the thread/option you mention, so I have not attempted 
to boot the RPi2 U-Boot in secure mode. If you're lucky, U-Boot itself 
will "just work" once TEXT_BASE is fixed.

To boot a kernel, you'll probably need to at least configure the ARM 
architected timers CNTFRQ register for the kernel. Perhaps there are a 
few other things like that missing?

It might be interesting to enable U-Boot's PSCI support on the RPi2, so 
that an upstream kernel could gain SMP support without the need for 
explicit BCM2836 SMP support code.

So far, I haven't attempted anything with an (upstream) kernel on RPi2, 
just U-Boot.