On Tue, Jan 28, 2020 at 10:48:29AM -0500, Tom Rini wrote:

Hey all,

Relatively recently it's been highlighted that a number of boards are disabling relocation of the device tree image in memory and this in turn leading to various difficult to resolve bugs. At heart, disabling device tree relocation at boot is something that should be used in rare circumstances (and more generally fdt_high / initrd_high set to where they are already residing in memory, as a known, correct and aligned address).

I would like to ask everyone to update their board config file to use the bootm_size (or set CONFIG_SYS_BOOTMAPSZ) to the amount of memory (size, not location) available to safely contain a kernel, device tree and initrd for relocation. Thanks all!

To offer a additional guidance here, in include/configs/ti_armv7_common.h I did the following a while ago: /* * We setup defaults based on constraints from the Linux kernel, which should * also be safe elsewhere. We have the default load at 32MB into DDR (for * the kernel), FDT above 128MB (the maximum location for the end of the * kernel), and the ramdisk 512KB above that (allowing for hopefully never * seen large trees). We say all of this must be within the first 256MB * as that will normally be within the kernel lowmem and thus visible via * bootm_size and we only run on platforms with 256MB or more of memory. */ #define DEFAULT_LINUX_BOOT_ENV \ "loadaddr=0x82000000\0" \ "kernel_addr_r=0x82000000\0" \ "fdtaddr=0x88000000\0" \ "fdt_addr_r=0x88000000\0" \ "rdaddr=0x88080000\0" \ "ramdisk_addr_r=0x88080000\0" \ "scriptaddr=0x80000000\0" \ "pxefile_addr_r=0x80100000\0" \ "bootm_size=0x10000000\0" \ "boot_fdt=try\0 Note that these platforms have a DRAM base of 0x8000_0000. The offsets described above are based on Documentation/arm/booting.rst in the Linux Kernel and were the best-generic-fit I could come up with given those constraints and suggestions. I don't know of a best-practices example for arm64 platforms right now. While I believe that cmd/booti.c makes sure to follow the requirements of Documentation/arm64/booting.rst it would be good to audit it again for any recent updates.

Hope this helps and thanks!