[U-Boot] [PATCH] ARM: make ARMV7_LPAE select PHYS_64BIT

[Masahiro Yamada]

Hi Alex,


2016-08-11 22:50 GMT+09:00 Alexander Graf <agraf at suse.de>:
>
>
> On 11.08.16 15:36, Masahiro Yamada wrote:
>> As you see in arch/arm/include/asm/types.h, CONFIG_PHYS_64BIT
>> determines the size of phys_addr_t.  The ARM Large Physical Address
>> Extension allows CPUs to access a physical address space larger than
>> 4GB, so the physical address may not fit in 32bit long phys_addr_t.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro at socionext.com>
>> ---
>>
>> I did Buildman test, but not run-time test.
>>
>> Looks like bcm283x (RPI) is the only arch that selects ARMV7_LPAE,
>> so I hope Stephen will check this patch.
>
> Well, the bcm2837 still only has a 32bit bus, so we can't actually make
> use of addresses bigger than 32bits.
>
> I think it would make most sense to select PHYS_64BIT on whatever 32bit
> SoC actually needs to accesses memory above 4GB.
>
> The main reason for having LPAE support for armv7 is not to support
> higher addresses (we still map everything 1:1 usually), it's to allow
> running in HYP mode which requires LPAE style page tables.

Thanks for explaining this.
Then, please forget about this patch.


-- 
Best Regards
Masahiro Yamada