[U-Boot] [PATCH v3 00/13] ARMv7: add PSCI support to u-boot

[Albert ARIBAUD]

Hi Marc,

On Thu, 17 Apr 2014 09:58:19 +0100, Marc Zyngier <marc.zyngier at arm.com>
wrote:

> On Thu, Apr 17 2014 at  9:34:24 am BST, Albert ARIBAUD <albert.u.boot at aribaud.net> wrote:
> > Hi Marc,
> >
> > On Wed, 16 Apr 2014 17:09:07 +0100, Marc Zyngier <marc.zyngier at arm.com>
> > wrote:
> >
> >> On 16/04/14 15:45, Albert ARIBAUD wrote:
> >> > Hi Marc,
> >> > 
> >> > On Sat, 15 Feb 2014 13:36:24 +0000, Marc Zyngier
> >> > <marc.zyngier-5wv7dgnIgG8 at public.gmane.org> 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 turn some of the existing u-boot code into a
> >> >> separate section that can live in secure RAM (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.
> >> >>
> >> >> This patch series contains 4 parts:
> >> >> - the first four patches are just bug fixes
> >> >> - the next two refactor the HYP/non-secure code to allow relocation
> >> >>   in secure memory
> >> >> - the next four contain the generic PSCI code and DT infrastructure
> >> >> - the last three implement the CPU_ON method of the Allwinner A20 (aka sun7i).
> >> >>
> >> >> I realize the A20 u-boot code is not upstream yet (BTW is anyone
> >> >> actively working on that?), but hopefully that should give a good idea
> >> >> of how things are structured so far. The patches are against the
> >> >> mainline u-boot tree as of today, merged with the sunxi u-boot tree
> >> >> of the day and the first 10 patches will directly apply to mainline
> >> >> u-boot.
> >> >>
> >> >> As for using this code, it goes like this:
> >> >> sun7i# ext2load mmc 0:1 0x40008000 zImage ; ext2load mmc 0:1 0x60000000 sun7i-a20-cubietruck.dtb
> >> >> 2270120 bytes read in 117 ms (18.5 MiB/s)
> >> >> 9138 bytes read in 3 ms (2.9 MiB/s)
> >> >> sun7i# fdt addr 0x60000000 ; fdt resize ; fdt set ethernet0 mac-address "[5a fe b0 07 b0 07]"
> >> >> sun7i# setenv bootargs console=ttyS0,115200 earlyprintk ip=dhcp root=/dev/nfs nfsroot=/backup/a20_root,tcp
> >> >> sun7i# bootz 0x40008000 - 0x60000000
> >> >>
> >> >> The kernel now boots in HYP mode, finds its secondary CPU without any
> >> >> SMP code present in the kernel, and runs KVM out of the box.
> >> >> I've been told the Xen/ARM guys managed to do the same fairly easily.
> >> >>
> >> >> This code has also been tested on a VExpress TC2, running KVM with all
> >> >> 5 CPUs, in order to make sure there was no obvious regression.
> >> >>
> >> >> I'm wildly cross-posting this patch series, including to lists I'm not
> >> >> subscribed to. Please keep me on Cc for any comment you may have.
> >> >>
> >> >> The code is also available at:
> >> >> git://git.kernel.org/pub/scm/linux/kernel/git/maz/u-boot.git wip/psci
> >> >>
> >> >> Cheers,
> >> >>
> >> >>         M.
> >> > 
> >> > Marc, I'm unclear what you want to do with this series. You mention
> >> > that its first 10 patches will apply to U-Boot, but I am not sure
> >> > whether you are just indicating that it is possible to apply them or
> >> > asking for these 10 patches to go in U-Boot mainline.  Or is it
> >> > something else yet?
> >> 
> >> Well, I rarely write code just for the sake of forking a critical
> >> project ;-)
> >> 
> >> So let's be 100% explicit: Yes, I'm hereby asking for these patches to
> >> be merged. They offer a service that is required by the Linux kernel as
> >> well as Xen. They are in active use on the Allwinner sun7i platform as
> >> well as Versatile Express (though the later doesn't have a PSCI
> >> implementation).
> >> 
> >> Now, given that two months have gone past without much comment other
> >> than the odd "hey, works great", I don't really know where to take that.
> >> 
> >> Are you willing to review the patches?
> >
> > Well, I rarely ask about patches just for the sake of conversation. O:-)
> >
> > So yes, I am willing to review them -- and I suspect others are, as
> > well. Nobody commented the V3 series on the U-Boot list -- save for
> > Jon's comment about the series needing a rebase -- which could mean no
> > one here is unhappy with them... or they were discussed and possibly
> > acted upon on linux-sunxi, where the replies were redirected. I don't
> > follow linux-sunx closely, so I couldn't tell. :)
> 
> No, so far there hasn't been much discussion, and people seem happy with
> it. I have a couple of fixes lined up, but nothing major.
> 
> Also, a number of the patches are actually fixes that should really make
> it into the U-Boot tree, no matter if the PSCI code is merged or
> not. Some of them make the kernel go completely bonkers, other introduce
> the risk of U-Boot falling over in style.
> 
> > Still, I am trying to figure out the whole Allwinner nebula and see how
> > things are supposed to work out between their various SoCs and make
> > sure to avoid duplicate/incompatible effort (you're mentioning the A20,
> > there seems to be A31 work underway too elsewhere). I am starting to
> > wonder whether an ARM allwinner sub-repo might make sense. Tom,
> > Wolfgang?
> 
> Ian Campbell (cc-ed) is actively pushing out patches to support the A20
> in mainline U-Boot (I believe you've been on the receiving end of
> these), and I plan to rebase my series on top of his. Still, the A20
> support is only a small part of the code, used as an example of how to
> implement PSCI on a rather simple platform. This can easily be split out
> and merged via different trees.

I have seen Ian's patches, but didn't have time until now to look at
them.

OK, so, to me, the best course of actions is to:

1) isolate those patches in your series which are fixes unrelated to
AllWinner SoCs and get them in. I'd prefer a separate series for this.

2) Get Ian's Allwinner-related patches (reviewed and) applied.

3) Get your Allwinner-related patches (reviewed and) applied.

> Thanks,
> 
> 	M.

Amicalement,
-- 
Albert.