[U-Boot] [linux-sunxi] [RFC PATCH 8/8] sunxi: enable PSCI for A83T SoC

[icenowy at aosc.io]

在 2017-06-23 21:35，Maxime Ripard 写道：
> On Fri, Jun 23, 2017 at 09:24:25PM +0800, icenowy at aosc.io wrote:
>> 在 2017-06-07 20:51，Marc Zyngier 写道：
>> > On 07/06/17 13:12, Icenowy Zheng wrote:
>> > >
>> > >
>> > > 于 2017年6月7日 GMT+08:00 下午8:11:12, Marc Zyngier
>> > > <marc.zyngier at arm.com> 写到:
>> > > > On 07/06/17 08:00, Chen-Yu Tsai wrote:
>> > > > > On Wed, Jun 7, 2017 at 2:50 PM, Maxime Ripard
>> > > > > <maxime.ripard at free-electrons.com> wrote:
>> > > > > > On Wed, Jun 07, 2017 at 11:47:24AM +0800, Chen-Yu Tsai wrote:
>> > > > > > > On Wed, Jun 7, 2017 at 11:40 AM, Icenowy Zheng <icenowy at aosc.io>
>> > > > wrote:
>> > > > > > > >
>> > > > > > > >
>> > > > > > > > 于 2017年6月7日 GMT+08:00 上午11:36:27, Chen-Yu
>> > > > > > > > Tsai <wens at csie.org> 写到:
>> > > > > > > > > On Wed, Jun 7, 2017 at 8:47 AM, Icenowy Zheng <icenowy at aosc.io>
>> > > > wrote:
>> > > > > > > > > > As we have now a basical implementation
>> > > > > > > > > > of PSCI for A83T, enable
>> > > > > > > > > > non-secure boot support and PSCI on A83T now.
>> > > > > > > > > >
>> > > > > > > > > > Signed-off-by: Icenowy Zheng <icenowy at aosc.io>
>> > > > > > > > > > ---
>> > > > > > > > > >  arch/arm/mach-sunxi/Kconfig | 4 ++++
>> > > > > > > > > >  1 file changed, 4 insertions(+)
>> > > > > > > > > >
>> > > > > > > > > > diff --git a/arch/arm/mach-sunxi/Kconfig
>> > > > > > > > > b/arch/arm/mach-sunxi/Kconfig
>> > > > > > > > > > index 7ced838d6a..31d29de428 100644
>> > > > > > > > > > --- a/arch/arm/mach-sunxi/Kconfig
>> > > > > > > > > > +++ b/arch/arm/mach-sunxi/Kconfig
>> > > > > > > > > > @@ -98,8 +98,12 @@ config MACH_SUN8I_A33
>> > > > > > > > > >  config MACH_SUN8I_A83T
>> > > > > > > > > >         bool "sun8i (Allwinner A83T)"
>> > > > > > > > > >         select CPU_V7
>> > > > > > > > > > +       select CPU_V7_HAS_NONSEC
>> > > > > > > > > > +       select CPU_V7_HAS_VIRT
>> > > > > > > > > > +       select ARCH_SUPPORT_PSCI
>> > > > > > > > > >         select SUNXI_GEN_SUN6I
>> > > > > > > > > >         select SUPPORT_SPL
>> > > > > > > > > > +       select ARMV7_BOOT_SEC_DEFAULT if
>> > > > > > > > > > OLD_SUNXI_KERNEL_COMPAT
>> > > > > > > > >
>> > > > > > > > > The kernel does not work yet. Please have it boot to secure by
>> > > > default
>> > > > > > > > > regardless of the kernel. We can have it
>> > > > > > > > > boot non-secure once the
>> > > > > > > > > kernel
>> > > > > > > > > has been working for a reasonable amount of time.
>> > > > > > > > >
>> > > > > > > > > I don't want clueless users coming and asking why it suddenly
>> > > > stopped
>> > > > > > > > > working. This should be an experimental feature.
>> > > > > > > >
>> > > > > > > > Maybe you should send out the fix, and tag them to also apply to
>> > > > > > > > stable tree.
>> > > > > > > >
>> > > > > > > > GIC is really broken, UP systems only work by chance. We
>> > > > > > > > shouldn't depend on this behavior.
>> > > > > > >
>> > > > > > > As I previously explained, it is not the GIC that is broken. I
>> > > > believe
>> > > > > > > the GIC is working exactly as it is supposed to with
>> > > > > > > regards to its
>> > > > > > > input signals.
>> > > > > > >
>> > > > > > > Allwinner's security extensions implementation simply does not
>> > > > properly
>> > > > > > > forward the AXI secure bit when the e-fuse's secure bit isn't
>> > > > burned.
>> > > >
>> > > > Arghh. Puke. Now I remember this, and I wish I didn't...
>> > > >
>> > > > > > Is that on all revisions, or just the revB ?
>> > > > >
>> > > > > It's the A80, but I'm guessing the same applies to the A83T. It's
>> > > > more
>> > > > > of a guess really, but I think it's a logical one. If the e-fuse
>> > > > isn't
>> > > > > programmed, the TZPC doesn't work, and access to all secure
>> > > > peripherals
>> > > > > still work, even from non-secure mode. The only one that
>> > > > > does work is
>> > > > > the secure SRAM.
>> > > > >
>> > > > > The GIC still has the banked secure/non-secure registers, just that
>> > > > all
>> > > > > cores access the secure bank, even when in non-secure mode. The
>> > > > workaround
>> > > > > is to use the alias set of non-secure registers in Linux.
>> > > >
>> > > > That's a pretty dire workaround. Also, I expect that secure writes to
>> > > > GICV/GICH will not do the right thing. At this point, what is the
>> > > > requirement for running non-secure?
>> > >
>> > > Write Secure Boot eFUSE, which will break *all* existing softwares.
>> >
>> > Don't do it, then.
>> >
>> > Any other *real* use case for running non-secure? As in "Stuff that
>> > would benefit to a user"? Because if the answer is "none" as I suspect
>> > it is, you might as well keep the system in secure mode.
>> 
>> Maybe we should then use legacy SMP bringup method (code in kernel)
>> rather than PSCI?
> 
> I guess it all depends on the answer to Marc's question. If
> virtualization doesn't work, then we don't have any incentive anymore
> to use PSCI and that would be a sensible option, yes.

I remember non-secure is a dependency for virtualization (HYP mode).

So if we do not do the workaround on GIC, we won't have stable
non-secure, then we won't have HYP mode, then we can drop PSCI.

> 
> Maxime
> 
> --
> Maxime Ripard, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com