[U-Boot] [PATCH 2/2] sunxi: Set the AUXCR L2EN bit for sun4i/sun5i in FEL boot mode

[Siarhei Siamashka <siarhei.siamashka@gmail.com>]

On Mon, 21 Jul 2014 21:59:51 +0100
Ian Campbell <ijc@hellion.org.uk> wrote:

> On Mon, 2014-07-21 at 22:39 +0200, Jeroen Hofstee wrote:
> > Hello Ian,
> > 
> > On 21-07-14 22:07, Ian Campbell wrote:
> > > On Fri, 2014-07-18 at 20:47 +0200, Jeroen Hofstee wrote:
> > >> Hello Siarhei,
> > >>
> > >> On 18-07-14 19:09, Siarhei Siamashka wrote:
> > >>> This is needed to have feature parity with the normal boot mode,
> > >>> where the L2EN bit in the CP15 Auxiliary Control Register is set
> > >>> by the BROM code right from the start.
> > >>>
> > >>> If this is not done, the Linux system ends up booted with the L2 cache
> > >>> disabled.
> > >>>
> > >> I don't know a single about the sunxi, but shouldn't linux
> > >> be patched instead. The commit message seems to indicate
> > >> it is not an u-boot issue.
> > > The ACTLR may not be writeable from NS mode so it has to be setup in the
> > > bootloader before dropping to NS mode.
> > mmm, I guess there is something wrong with the boot sequence
> > if the kernel itself can't access raw hw.
> 
> Do you know what ARM Secure and Non-Secure worlds are?
> 
> The kernel expects to be launched in NS mode and simply cannot access
> this register. This is a feature not a bug.

Just curious. Is there a modern consensus about how this all is
supposed to be done nowadays?

The last time I read anything about this subject was the following
longish and already old discussion thread (which has probably
already lost relevance):
    http://lists.linaro.org/pipermail/boot-architecture/2011-August/000060.html

Since the Allwinner BROM does not forcefully drop us to the non-secure
mode, we have the absolute freedom of choice and may implement any
policy.

-- 
Best regards,
Siarhei Siamashka