[U-Boot] [PATCH 4/9] tegra: Replace home grown mmu code with generic table approach

[Stephen Warren]

On 02/23/2016 03:37 AM, Michal Simek wrote:
> On 22.2.2016 19:28, Stephen Warren wrote:
>> On 02/21/2016 06:57 PM, Alexander Graf wrote:
>>> Now that we have nice table driven page table creating code that gives
>>> us everything we need, move to that.
>>
>>> diff --git a/include/configs/tegra210-common.h
>>> b/include/configs/tegra210-common.h
>>
>>> +#define CONFIG_SYS_FULL_VA
>>> +#define CONFIG_SYS_MEM_MAP {                        \
>>> +    {                                \
>>> +        .base = 0x0UL,                        \
>>> +        .size = 0x80000000UL,                    \
>>> +        .attrs = PTE_BLOCK_MEMTYPE(MT_DEVICE_NGNRNE) |        \
>>> +             PTE_BLOCK_NON_SHARE |                \
>>> +             PTE_BLOCK_PXN | PTE_BLOCK_UXN            \
>>> +    }, {                                \
>>> +        .base = 0x80000000UL,                    \
>>> +        .size = 0xff80000000UL,                    \
>>> +        .attrs = PTE_BLOCK_MEMTYPE(MT_NORMAL) |            \
>>> +             PTE_BLOCK_INNER_SHARE                \
>>> +    },                                \
>>> +    }
>>
>> I'd prefer a layout that didn't align the closing } for different
>> nesting levels in the same column. To avoid indenting everything a lot,
>> it seems simplest to pull the final } back into the first column.
>>
>> I believe the .size field of the second entry in the array only needs to
>> be 0x80000000. Testing with a PCIe Ethernet card on p2371-2180 (the
>> driver for which sets up noncached entries in the page tables, hence
>> should exercise all this code) confirms that.
>>
>> While recent Tegra systems do support more than 2GB of RAM, U-Boot will
>> itself only use the first 2GB, so that PAs over 4GB are not used. See
>> board_get_usable_ram_top() in arch/arm/mach-tegra/board2.c. That's
>> because some peripherals can only access 32-bit PAs, and the simplest
>> way to accommodate that is to ignore any RAM above the 32-bit limit.
>
> Didn't you use mtest to test memory above of 2GB?

It looks like we don't have mtest enabled.

However, I was able to use itest to confirm that RAM > 4GB PA does work 
with this patch. I suppose we may as well leave it enabled then.