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ARM: tegra: restrict usable RAM size further

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Additionally, ARM64 devices typically run a secure monitor in EL3 and
U-Boot in EL2, and set up some secure RAM carve-outs to contain the EL3
code and data. These carve-outs are located at the top of 32-bit address
space. Restrict U-Boot's RAM usage to well below the location of those
carve-outs. Ideally, we would the secure monitor would inform U-Boot of
exactly which RAM it could use at run-time. However, I'm not sure how to
do that at present (and even if such a mechanism does exist, it would
likely not be generic across all forms of secure monitor).

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>
This commit is contained in:
Stephen Warren 2015-07-29 13:47:58 -06:00 committed by Tom Warren
parent 1264f0f6c6
commit 424afc0a95
1 changed files with 11 additions and 2 deletions
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13
arch/arm/mach-tegra/board2.c
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@ -290,11 +290,20 @@ void pad_init_mmc(struct mmc_host *host)
* 32-bits of the physical address space. Cap the maximum usable RAM area
* at 4 GiB to avoid DMA buffers from being allocated beyond the 32-bit
* boundary that most devices can address.
*
* Additionally, ARM64 devices typically run a secure monitor in EL3 and
* U-Boot in EL2, and set up some secure RAM carve-outs to contain the EL3
* code and data. These carve-outs are located at the top of 32-bit address
* space. Restrict U-Boot's RAM usage to well below the location of those
* carve-outs. Ideally, we would the secure monitor would inform U-Boot of
* exactly which RAM it could use at run-time. However, I'm not sure how to
* do that at present (and even if such a mechanism does exist, it would
* likely not be generic across all forms of secure monitor).
*/
ulong board_get_usable_ram_top(ulong total_size)
{
if (gd->ram_top > 0x100000000)
return 0x100000000;
if (gd->ram_top > 0xe0000000)
return 0xe0000000;
return gd->ram_top;
}