Re: [PATCH] board: rpi: Update memory layout for Aarch64

[Tom Rini <trini@konsulko.com>]

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On Wed, Jul 17, 2024 at 03:32:00PM -0300, Walter Lozano wrote:
> 
> 
> On 7/17/24 12:44, Tom Rini wrote:
> > On Wed, Jul 17, 2024 at 11:59:50AM +0100, Peter Robinson wrote:
> > > On Tue, 16 Jul 2024 at 18:21, Tom Rini <trini@konsulko.com> wrote:
> > > > 
> > > > On Tue, Jul 16, 2024 at 02:16:02PM -0300, Walter Lozano wrote:
> > > > 
> > > > > ARM and Aarch64 have different restrictions and trying to accommodate
> > > > > larger kernels like the ones used in distros can be challenging. For this
> > > > > reason, separate the layout and rearrange the map for Aarch64 to support
> > > > > kernels larger than 36 MB.
> > > > > 
> > > > > Signed-off-by: Walter Lozano <walter.lozano@collabora.com>
> > > > > ---
> > > > > 
> > > > >   board/raspberrypi/rpi/rpi.env | 25 ++++++++++++++++++-------
> > > > >   1 file changed, 18 insertions(+), 7 deletions(-)
> > > > > 
> > > > > diff --git a/board/raspberrypi/rpi/rpi.env b/board/raspberrypi/rpi/rpi.env
> > > > > index 30228285edd..37c7f6a920e 100644
> > > > > --- a/board/raspberrypi/rpi/rpi.env
> > > > > +++ b/board/raspberrypi/rpi/rpi.env
> > > > > @@ -42,13 +42,19 @@ dfu_alt_info+=zImage fat 0 1
> > > > >    *   For Aarch64, the kernel image is uncompressed and must be loaded at
> > > > >    *   text_offset bytes (specified in the header of the Image) into a 2MB
> > > > >    *   boundary. The 'booti' command relocates the image if necessary. Linux uses
> > > > > - *   a default text_offset of 0x80000.  In summary, loading at 0x80000
> > > > > - *   satisfies all these constraints and reserving memory up to 0x02400000
> > > > > - *   permits fairly large (roughly 36M) kernels.
> > > > > + *   a default text_offset of 0x80000.  However, loading it at 0x80000
> > > > > + *   will allow to reserve only up to 0x02400000 which permits medium size
> > > > > + *   kernels (roughly 36M). This is good enough for customized kernels but
> > > > > + *   not for distros which by default enable drivers for many different
> > > > > + *   boards. Under these circumstances, using 0x00200000 provides room for
> > > > > + *   larger kernels.
> > > > >    *
> > > > >    * scriptaddr and pxefile_addr_r can be pretty much anywhere that doesn't
> > > > >    * conflict with something else. Reserving 1M for each of them at
> > > > > - * 0x02400000-0x02500000 and 0x02500000-0x02600000 should be plenty.
> > > > > + * 0x02400000-0x02500000 and 0x02500000-0x02600000 should be plenty for ARM.
> > > > > + *
> > > > > + *   For Aarch64, since the kernel is placed in different location,
> > > > > + *   accommodate them to reserver 1M for each of them.
> > > > >    *
> > > > >    * On ARM, both the DTB and any possible initrd must be loaded such that they
> > > > >    * fit inside the lowmem mapping in Linux. In practice, this usually means not
> > > > > @@ -62,16 +68,21 @@ dfu_alt_info+=zImage fat 0 1
> > > > >    * large initrds before they start colliding with U-Boot.
> > > > >    */
> > > > >   #ifdef CONFIG_ARM64
> > > > > +pxefile_addr_r=0x00080000
> > > > > +scriptaddr=0x00100000
> > > > > +kernel_addr_r=0x00200000
> > > > > +fdt_addr_r=0x03400000
> > > > > +ramdisk_addr_r=0x03500000
> > > > >   fdt_high=ffffffffffffffff
> > > > >   initrd_high=ffffffffffffffff
> > > > >   #else
> > > > > -fdt_high=ffffffff
> > > > > -initrd_high=ffffffff
> > > > > -#endif
> > > > >   kernel_addr_r=0x00080000
> > > > >   scriptaddr=0x02400000
> > > > >   pxefile_addr_r=0x02500000
> > > > >   fdt_addr_r=0x02600000
> > > > >   ramdisk_addr_r=0x02700000
> > > > > +fdt_high=ffffffff
> > > > > +initrd_high=ffffffff
> > > > > +#endif
> > > > > 
> > > > >   boot_targets=mmc usb pxe dhcp
> > > > 
> > > > We need to drop the disabling of device tree / initrd relocation as
> > > > that's sure not going to help matters. What's the minimum amount of
> > > > memory an aarch64 Pi will have? I really prefer reserving 128MiB (even
> > > > if that's not the maximum Linux Kernel Image size anymore) and then
> > > > device tree and then initrd.
> > > 
> > > 512Mb on the Zero2W and RPi3A.
> > > 
> > > We've not seen an issue here on the very large Fedora kernel, but I
> > > suspect that's because using UEFI mitigates this somewhat because here
> > > we're actually loading shim/grub.
> > 
> > OK, that should be enough to put a 128MiB spot for kernel, then 512KiB
> > for device tree, and then rest for initrd, and not be disabling
> > relocation (and thus preventing U-Boot from fixing failures).
> > 
> 
> Thanks for the feedback! If I understood it correctly a layout like the
> the one bellow would be the right thing. The only difference is in
> device tree for which is reserved a bit more.
> 
> pxefile_addr_r=0x00080000
> scriptaddr=0x00100000
> kernel_addr_r=0x00200000
> fdt_addr_r=0x09800000
> ramdisk_addr_r=0x09900000
> 
> If this matches the expectations I will prepare the V2.

Looks right to me, Peter or Matthias ? Thanks!

-- 
Tom

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