Hi Stephen, On 23 December 2014 at 10:34, Stephen Warren <swar...@wwwdotorg.org> wrote: > From: Stephen Warren <swar...@nvidia.com> > > 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 want 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, we can't use get_ram_size() to verify the actual amount of RAM > present on such systems, since some of the RAM can't be accesses, which
accessed > confuses that function. Avoid calling get_ram_size() when the RAM size > is too large for it to work correctly. It's never actually needed anyway, > since there's no reason for the BCT to report the wrong RAM size. > > In systems with >=4GB RAM, we still need to clip the reported RAM size > since U-Boot uses a 32-bit variable to represent the RAM size in bytes. > > Signed-off-by: Stephen Warren <swar...@nvidia.com> Reviewed-by: Simon Glass <s...@chromium.org> > --- > arch/arm/cpu/tegra-common/board.c | 22 +++++++++++++++++++++- > 1 file changed, 21 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/cpu/tegra-common/board.c > b/arch/arm/cpu/tegra-common/board.c > index f16fe68a6649..87511a31df18 100644 > --- a/arch/arm/cpu/tegra-common/board.c > +++ b/arch/arm/cpu/tegra-common/board.c > @@ -40,7 +40,27 @@ unsigned int query_sdram_size(void) > size_bytes = get_ram_size((void *)PHYS_SDRAM_1, emem_cfg * 1024); > #else > debug("mc->mc_emem_cfg (MEM_SIZE_MB) = 0x%08x\n", emem_cfg); > - size_bytes = get_ram_size((void *)PHYS_SDRAM_1, emem_cfg * 1024 * > 1024); > + /* > + * If >=4GB RAM is present, the byte RAM size won't fit into 32-bits > + * and will wrap. Clip the reported size to the maximum that a 32-bit > + * variable can represent (rounded to a page). > + */ > + if (emem_cfg >= 4096) { > + size_bytes = U32_MAX & ~(0x1000 - 1); Will this return 4GB - 4KB? Why not return the full size? > + } else { > + /* RAM size EMC is programmed to. */ > + size_bytes = emem_cfg * 1024 * 1024; > + /* > + * If all RAM fits within 32-bits, it can be accessed without > + * LPAE, so go test the RAM size. Otherwise, we can't access > + * all the RAM, and get_ram_size() would get confused, so > + * avoid using it. There's no reason we should need this > + * validation step anyway. > + */ > + if (emem_cfg <= (0 - PHYS_SDRAM_1) / (1024 * 1024)) > + size_bytes = get_ram_size((void *)PHYS_SDRAM_1, > + size_bytes); > + } > #endif > > #if defined(CONFIG_TEGRA30) || defined(CONFIG_TEGRA114) > -- > 1.9.1 > Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot