u-boot: rpi: Enlarge space available for kernel.

[Simon Glass]

Hi,

On Mon, 16 Sept 2024 at 23:06, Vagrant Cascadian <vagrant at debian.org> wrote:
>
> On 2024-09-16, Herman Rimm wrote:
> > --- /dev/null
> > +++ b/gnu/packages/patches/u-boot-50M-kernel.patch
> > @@ -0,0 +1,51 @@
> > +This patch configures the U-Boot for Raspberry Pis to reserve 50 MB for
> > +linux kernels, because the 6.9 and newer linux-libre-arm64-generic
> > +kernels can be larger than 36 MB.  It was created by Herman Rimm
> > +<herman at rimm.ee> in August 2024 and is not submitted upstream yet.
> > +diff --git a/board/raspberrypi/rpi/rpi.env b/board/raspberrypi/rpi/rpi.env
> > +index 30228285ed..54a8e9e5ae 100644
> > +--- a/board/raspberrypi/rpi/rpi.env
> > ++++ b/board/raspberrypi/rpi/rpi.env
> > +@@ -43,22 +43,22 @@ dfu_alt_info+=zImage fat 0 1
> > +  *   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.
> > ++ *   satisfies all these constraints and reserving memory up to 0x03400000
> > ++ *   permits fairly large (roughly 50M) 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.
> > ++ * 0x03200000-0x03300000 and 0x03300000-0x03400000 should be plenty.
> > +  *
> > +  * 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
> > +  * more than ~700M away from the start of the kernel image but this number can
> > +  * be larger OR smaller depending on e.g. the 'vmalloc=xxxM' command line
> > +  * parameter given to the kernel. So reserving memory from low to high
> > +- * satisfies this constraint again. Reserving 1M at 0x02600000-0x02700000 for
> > +- * the DTB leaves rest of the free RAM to the initrd starting at 0x02700000.
> > ++ * satisfies this constraint again. Reserving 1M at 0x03400000-0x03500000 for
> > ++ * the DTB leaves rest of the free RAM to the initrd starting at 0x03500000.
> > +  * Even with the smallest possible CPU-GPU memory split of the CPU getting
> > +- * only 64M, the remaining 25M starting at 0x02700000 should allow quite
> > ++ * only 64M, the remaining 11M starting at 0x03500000 should allow quite
> > +  * large initrds before they start colliding with U-Boot.
> > +  */
> > + #ifdef CONFIG_ARM64
> > +@@ -69,9 +69,9 @@ 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
> > ++scriptaddr=0x03200000
> > ++pxefile_addr_r=0x03300000
> > ++fdt_addr_r=0x03400000
> > ++ramdisk_addr_r=0x03500000
> > +
> > + boot_targets=mmc usb pxe dhcp
>
> I would really like to hear comments from the upstream u-boot
> maintainers on adjusting these values...

It is fine to adjust them, so long as the memory is actually there. I
don't know of anything special about the current values.

Regards,
Simon