arm: rpi: Increase headroom available to kernel image when relocated

We are seeing the following issue booting when moving to the v6.8.x kernel releases:

Moving Image from 0x80000 to 0x200000, end=2600000
## Flattened Device Tree blob at 02600000
   Booting using the fdt blob at 0x2600000
ERROR: FDT image overlaps OS image (OS=0x200000..0x2600000)

This is a result of the kernel images now reporting a size of 36MB and just hitting the offset used for the DTB when the kernel is relocated to a 2MB boundary (as is required for booting).

The kernel is being loaded at 0x80000 on the assumption that the kernel image would be compressed. Our kernel isn't compressed, so copy to the required boot location to avoid the need to relocate.

This frees up 1.5MB before the kernel image, so shift the PXE and script load locations to before the kernel. Shift up the DTB and initrd allocations to increase the kernel allocation to 50MB, giving headroom for the kernel image to grow.

Signed-off-by: Martyn Welch martyn.welch@collabora.com

debian/patches/apertis/rpi/0049-arm-rpi-Increase-headroom-available-to-kernel-image-.patch

+From: Martyn Welch <martyn.welch@collabora.com>
+Date: Fri, 14 Jun 2024 16:57:25 +0100
+Subject: arm: rpi: Increase headroom available to kernel image when relocated
+
+We are seeing the following issue booting when moving to the v6.8.x
+kernel releases:
+
+   Moving Image from 0x80000 to 0x200000, end=2600000
+   ## Flattened Device Tree blob at 02600000
+      Booting using the fdt blob at 0x2600000
+   ERROR: FDT image overlaps OS image (OS=0x200000..0x2600000)
+
+This is a result of the kernel images now reporting a size of 36MB and
+just hitting the offset used for the DTB when the kernel is relocated to
+a 2MB boundary (as is required for booting).
+
+The kernel is being loaded at 0x80000 on the assumption that the kernel
+image would be compressed. Our kernel isn't compressed, so copy to the
+required boot location to avoid the need to relocate.
+
+This frees up 1.5MB before the kernel image, so shift the PXE and script
+load locations to before the kernel. Shift up the DTB and initrd
+allocations to increase the kernel allocation to 50MB, giving headroom
+for the kernel image to grow.
+
+Signed-off-by: Martyn Welch <martyn.welch@collabora.com>
+---
+ board/raspberrypi/rpi/rpi.env | 18 +++++++++++++-----
+ 1 file changed, 13 insertions(+), 5 deletions(-)
+
+diff --git a/board/raspberrypi/rpi/rpi.env b/board/raspberrypi/rpi/rpi.env
+index 96a3083..a70bedc 100644
+--- a/board/raspberrypi/rpi/rpi.env
++++ b/board/raspberrypi/rpi/rpi.env
+@@ -62,6 +62,14 @@ dfu_alt_info+=zImage fat 0 1
+  * Even with the smallest possible CPU-GPU memory split of the CPU getting
+  * only 64M, the remaining 25M starting at 0x02700000 should allow quite
+  * large initrds before they start colliding with U-Boot.
++ *
++ * APERTIS: As a distro kernel, we need more than 36M for the kernel, we are
++ *   also not booting a compressed kernel and with a kernel where the
++ *   test_offset is set to zero, so we can load directly to a 2MB boundary to
++ *   save a relocation. As we now have 1.5MB of free space before the kernel,
++ *   we shift to loading the PXE and script files there. We are not concerned
++ *   with supporting the smallest possible CPU-GPU split on the oldest
++ *   generations of RPi, so bump the space provided for the kernel to 50MB.
+  */
+ #ifdef CONFIG_ARM64
+ fdt_high=ffffffffffffffff
+@@ -70,10 +78,10 @@ initrd_high=ffffffffffffffff
+ 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
++pxefile_addr_r=0x00080000
++scriptaddr=0x00100000
++kernel_addr_r=0x00200000
++fdt_addr_r=0x03400000
++ramdisk_addr_r=0x03500000
+ 
+ boot_targets=mmc usb pxe dhcp

[Sjoerd Simons]

this should be ideally written in a way that would make sense upstream ;)

[Sjoerd Simons]

apertis specific notes will make it harder to upstream

[Walter Lozano]

What about having different configurations, one for ARM and another for ARM64? I think that in this way the impact will be reduced, and it will be clearer. Something like

#ifdef CONFIG_ARM64
fdt_high=ffffffffffffffff
initrd_high=ffffffffffffffff
pxefile_addr_r=0x00080000
scriptaddr=0x00100000
kernel_addr_r=0x00200000
fdt_addr_r=0x03400000
ramdisk_addr_r=0x03500000
#else
fdt_high=ffffffff
initrd_high=ffffffff
kernel_addr_r=0x00080000
scriptaddr=0x02400000
pxefile_addr_r=0x02500000
fdt_addr_r=0x02600000
ramdisk_addr_r=0x02700000
#endif

[Walter Lozano]

I have submitted my proposal upstream

https://patchwork.ozlabs.org/project/uboot/patch/20240716171602.2279766-1-walter.lozano@collabora.com/

[Walter Lozano]

I will wait a few days for feedback before preparing a MR for Apertis.

[Walter Lozano]

The new proposed approach is in !117 (merged)