From 1e4d11a58c0d68443c7953fff6577fd6d339a34b Mon Sep 17 00:00:00 2001 From: Stephen Warren Date: Tue, 23 Dec 2014 10:34:49 -0700 Subject: common: board: support systems with where RAM ends beyond 4GB Some systems have so much RAM that the end of RAM is beyond 4GB. An example would be a Tegra124 system (where RAM starts at 2GB physical) that has more than 2GB of RAM. In this case, we can gd->ram_size to represent the actual RAM size, so that the actual RAM size is passed to the OS. This is useful if the OS implements LPAE, and can actually use the "extra" RAM. However, U-Boot does not implement LPAE and so must deal with 32-bit physical addresses. To this end, we enhance board_get_usable_ram_top() to detect the "over-sized" case, and limit the relocation addres so that it fits into 32-bits of physical address space. Signed-off-by: Stephen Warren Reviewed-by: Simon Glass Signed-off-by: Tom Warren --- common/board_f.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'common') diff --git a/common/board_f.c b/common/board_f.c index 4d8b8a626b..62fdaebb54 100644 --- a/common/board_f.c +++ b/common/board_f.c @@ -360,6 +360,18 @@ static int setup_fdt(void) /* Get the top of usable RAM */ __weak ulong board_get_usable_ram_top(ulong total_size) { +#ifdef CONFIG_SYS_SDRAM_BASE + /* + * Detect whether we have so much RAM it goes past the end of our + * 32-bit address space. If so, clip the usable RAM so it doesn't. + */ + if (gd->ram_top < CONFIG_SYS_SDRAM_BASE) + /* + * Will wrap back to top of 32-bit space when reservations + * are made. + */ + return 0; +#endif return gd->ram_top; } -- cgit v1.2.1