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

[Tom Rini <trini@konsulko.com>]

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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.

-- 
Tom

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