From 0797f7f0b7e1d7853e2842ddc235ffef139fa792 Mon Sep 17 00:00:00 2001 From: Stephen Warren Date: Thu, 30 Aug 2018 15:43:44 -0600 Subject: [PATCH] ARM: tegra: reserve unmapped RAM so EFI doesn't use it 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 Signed-off-by: Alexander Graf --- 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 421a71b..12257a4 100644 --- a/arch/arm/mach-tegra/board2.c +++ b/arch/arm/mach-tegra/board2.c @@ -6,6 +6,7 @@ #include #include +#include #include #include #include @@ -210,6 +211,19 @@ int board_early_init_f(void) int board_late_init(void) { +#if CONFIG_IS_ENABLED(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 >> EFI_PAGE_SHIFT, + EFI_BOOT_SERVICES_DATA, false); + } +#endif + #if defined(CONFIG_TEGRA_SUPPORT_NON_SECURE) if (tegra_cpu_is_non_secure()) { printf("CPU is in NS mode\n");