On 09/01/2018 03:58 AM, Alexander Graf wrote:
From: Stephen Warren swarren@nvidia.com
Tegra U-Boot ensures that board_get_usable_ram_top() never returns a value over 4GB, since some peripherals can't access such addresses. However, on systems with more than 2GB of RAM, RAM bank 1 does describe this extra RAM, so that Linux (or whatever OS) can use it, subject to DMA limitations. Since board_get_usable_ram_top() points at the top of RAM bank 0, the memory locations describes by RAM bank 1 are not mapped by U-Boot's MMU configuration, and so cannot be used for anything.
For some completely inexplicable reason, U-Boot's EFI support ignores the value returned by board_get_usable_ram_top(), and EFI memory allocation routines will return values above U-Boot's RAM top. This causes U-Boot to crash when it accesses that RAM, since it isn't mapped by the MMU. One use-case where this happens is TFTP download of a file on Jetson TX1 (p2371-2180).
This change explicitly tells the EFI code that this extra RAM should not be used, thus avoiding the crash.
A previous attempt to make EFI honor board_get_usable_ram_top() was rejected. So, this patch will need to be replicated for any board that implements board_get_usable_ram_top().
Fixes: aa909462d018 ("efi_loader: efi_allocate_pages is too restrictive") Signed-off-by: Stephen Warren swarren@nvidia.com
Thanks, applied to efi-next
They don't seem to have shown up in u-boot/master though...