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 --- arch/arm/mach-tegra/board2.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/arch/arm/mach-tegra/board2.c b/arch/arm/mach-tegra/board2.c index 421a71b3014d..869d5d99d2fd 100644 --- a/arch/arm/mach-tegra/board2.c +++ b/arch/arm/mach-tegra/board2.c @@ -6,6 +6,7 @@
#include <common.h> #include <dm.h> +#include <efi_loader.h> #include <errno.h> #include <ns16550.h> #include <usb.h> @@ -210,6 +211,19 @@ int board_early_init_f(void)
int board_late_init(void) { +#ifdef CONFIG_EFI_LOADER + if (gd->bd->bi_dram[1].start) { + /* + * Only bank 0 is below board_get_usable_ram_top(), so all of + * bank 1 is not mapped by the U-Boot MMU configuration, and so + * we must prevent EFI from using it. + */ + efi_add_memory_map(gd->bd->bi_dram[1].start, + gd->bd->bi_dram[1].size / 4096, + EFI_RESERVED_MEMORY_TYPE, false); + } +#endif + #if defined(CONFIG_TEGRA_SUPPORT_NON_SECURE) if (tegra_cpu_is_non_secure()) { printf("CPU is in NS mode\n");