[PATCH 0/3] rpi: Tidy up booting

[Tom Rini]

On Fri, Dec 06, 2024 at 05:10:39PM -0700, Simon Glass wrote:
> Hi Tom,
> 
> On Fri, 6 Dec 2024 at 17:00, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Fri, Dec 06, 2024 at 04:56:31PM -0700, Simon Glass wrote:
> > > Hi Tom,
> > >
> > > On Fri, 6 Dec 2024 at 16:52, Tom Rini <trini at konsulko.com> wrote:
> > > >
> > > > On Fri, Dec 06, 2024 at 04:41:37PM -0700, Simon Glass wrote:
> > > > > Hi Tom,
> > > > >
> > > > > On Fri, 6 Dec 2024 at 12:41, Tom Rini <trini at konsulko.com> wrote:
> > > > > >
> > > > > > On Fri, Dec 06, 2024 at 12:17:49PM -0700, Simon Glass wrote:
> > > > > > > Hi Tom,
> > > > > > >
> > > > > > > On Fri, 6 Dec 2024 at 07:08, Tom Rini <trini at konsulko.com> wrote:
> > > > > > > >
> > > > > > > > On Fri, Dec 06, 2024 at 06:11:10AM -0700, Simon Glass wrote:
> > > > > > > >
> > > > > > > > > This series allows rpi to boot a compressed Ubuntu kernel with ~100MB
> > > > > > > > > ramdisk, by expanding the available space.
> > > > > > > > >
> > > > > > > > > It also tidies up some strange behaviour with the provided FDT, where a
> > > > > > > > > separate pointer is maintained to it, even though U-Boot has copied it
> > > > > > > > > and placed it in its own space. This avoids strange bugs where it
> > > > > > > > > accidentally gets overwritten when loading a file into memory.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Simon Glass (3):
> > > > > > > > >   rpi: Update environment to support booti and large initrd
> > > > > > > > >   fdt: Allow expanding the devicetree during relocation
> > > > > > > > >   rpi: Use the U-Boot control FDT for fdt_addr
> > > > > > > > >
> > > > > > > > >  board/raspberrypi/rpi/rpi.c   | 20 ++++++++------------
> > > > > > > > >  board/raspberrypi/rpi/rpi.env | 10 ++++++----
> > > > > > > > >  common/board_f.c              |  6 ++++--
> > > > > > > > >  dts/Kconfig                   | 11 +++++++++++
> > > > > > > > >  4 files changed, 29 insertions(+), 18 deletions(-)
> > > > > > > >
> > > > > > > > My feedback here is the same feedback I gave the last person that wanted
> > > > > > > > to update the Pi addresses, and I forget if they came back and did that
> > > > > > > > (and it's in Peter / Matthias' queue) or not. Disabling device tree
> > > > > > > > relocation is a bug and must be removed.
> > > > > > > >
> > > > > > > > After that, given the range of memory sizes available on Pi platforms,
> > > > > > > > allocating the kernel / initrd / kernel decompression buffer at run
> > > > > > > > time, ala mach-apple would make life easier in the long run.
> > > > > > >
> > > > > > > Yes, of course, but for now, this resolves the problem and I don't
> > > > > > > believe it creates any other problem.
> > > > > >
> > > > > > Yes. I think you missed that:
> > > > > > https://patchwork.ozlabs.org/project/uboot/patch/20240723193430.3050251-1-walter.lozano@collabora.com/
> > > > > > is also outstanding and should solve the problem.
> > > > >
> > > > > No, it doesn't support decompression, although I have to wonder why
> > > > > that patch was never applied.
> > > >
> > > > See Peter's response elsewhere about having a lot of things to do and
> > > > not a lot of time. I know he's intended to pick up and post a Pi PR for
> > > > a while.
> > >
> > > OK, but let's drop that patch since it doesn't support decompression, right?
> >
> > No? No one has done all of the work required (remove fdt_high /
> > initrd_high) and this also solves the larger kernel issue.
> 
> No, that is a separate issue. We need kernel_comp_addr and kernel_comp_size

Yes, those are required for automatic decompression, which is handy. But
the highest priority is removing fdt_high / initrd_high because those
lead to so much time being wasted by everyone. Your time digging in to
and making patch #2 for example.

> > > > > > > The solution should not be board-specific though. Once I have the
> > > > > > > bootstd files stuff is finished, I believe that bootstd will be able
> > > > > > > to do this and I plan to do this. Then the variables will be unused
> > > > > > > for rpi and we can just drop them for any bootstd boards.
> > > > > > >
> > > > > > > As of now, we have 390 boards using bootstd and 381 using distro
> > > > > > > scripts, so it is progress!
> > > > > >
> > > > > > Yes, it will be interesting to see what the future holds, and any of the
> > > > > > solutions handle some of the trickier corner cases that lead to the
> > > > > > current situation. Or perhaps the best outcome is that in current times,
> > > > > > those corner cases don't really appear anymore (with 512MiB DDR being
> > > > > > the lower bound for example on all the Pi families).
> > > > >
> > > > > Well rpi is a bit unusual...
> > > >
> > > > Sure, but not in this case? Lots of examples of multiple models with
> > > > different memory sizes, and especially with 32bit platforms smaller (by
> > > > current standards) overall DDR.
> > >
> > > I mean in the sense that it puts the devicetree in the middle of RAM.
> >
> > Which and where? Or do you mean it being exacerbated by disabling
> > relocation (which is why I keep going on and on about removing that from
> > platforms that do it)? Most platforms will load to the "middle" and
> > that's why you must not disable relocation because it's only a problem
> > when, well, relocation is disabled and U-Boot says "Gee, you're going to
> > break but you told me you want that, so, alright then."
> 
> No, the rpi relocates. I just mean that it puts the DT at about 512MB
> in RAM, which is annoying.

I guess we've once again lost some details. With fdt_high=0xffffffff we
do not relocate the device tree we're going to pass to the OS from
wherever it happens to be at the time. That is what I mean by
relocation. Looking at a Pi 4 here real quick, it has
fdtcontroladdr=3aea8b30. But if you mean fdt_addr, yes, that's around
512MiB (fdt_addr=2eff2d00) and likely the previous stage throwing it
there for the OS as a likely always accessible option.

-- 
Tom
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