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authorStephen Warren <swarren@nvidia.com>2014-12-23 10:34:51 -0700
committerTom Warren <twarren@nvidia.com>2015-03-04 10:08:56 -0700
commit56519c4f0498acdfb4dccd27bbb4b69a60cbb823 (patch)
tree69367e919018f8ce32ec52746447d7b0d935d28b
parent3a2cab512c0c4d96d8210e4f729dd080bbf8c90d (diff)
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ARM: tegra: support large RAM sizes
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 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 <swarren@nvidia.com> Reviewed-by: Simon Glass <sjg@chromium.org> Signed-off-by: Tom Warren <twarren@nvidia.com>
-rw-r--r--arch/arm/mach-tegra/board.c22
1 files changed, 21 insertions, 1 deletions
diff --git a/arch/arm/mach-tegra/board.c b/arch/arm/mach-tegra/board.c
index f16fe68..87511a3 100644
--- a/arch/arm/mach-tegra/board.c
+++ b/arch/arm/mach-tegra/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);
+ } 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)