[U-Boot] [PATCH 0/9] ARMv7: add PSCI support to u-boot

[Rob Herring]

On Thu, Nov 21, 2013 at 2:59 AM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> PSCI is an ARM standard that provides a generic interface that
> supervisory software can use to manage power in the following
> situations:
> - Core idle management
> - CPU hotplug
> - big.LITTLE migration models
> - System shutdown and reset
>
> It basically allows the kernel to offload these tasks to the firmware,
> and rely on common kernel side code.
>
> More importantly, it gives a way to ensure that CPUs enter the kernel
> at the appropriate exception level (ie HYP mode, to allow the use of
> the virtualization extensions), even across events like CPUs being
> powered off/on or suspended.
>
> The main idea here is to reuse some of the existing u-boot code to
> create a separate blob that can live in SRAM (or a reserved page of
> memory), containing a secure monitor that will implement the PSCI
> operations. This code will still be alive when u-boot is long gone,
> hence the need for a piece of memory that will not be touched by the
> OS.

Interesting. As a separate binary, I'm not sure this belongs or
benefits from being in u-boot. I would like to see this as a more
generic secure firmware loader or PSCI code be a part of u-boot code
directly. With the latter, you could extend it beyond PSCI to things
like env variable access (basically equivalent to UEFI runtime
services). I'm not saying we should do that though.

BTW, you will need to mark this region reserved in the dtb if in system RAM.

Rob