[U-Boot] [PATCH v2 2/6] sunxi: add Kconfig option for the maximum accessible DRAM

Chen-Yu Tsai
2018-03-23T09:42:19Z

On Fri, Mar 23, 2018 at 5:39 PM, Maxime Ripard
<maxime.ripard@bootlin.com> wrote:
> On Fri, Mar 23, 2018 at 04:18:53PM +0800, Icenowy Zheng wrote:
>> Allwinner 64-bit SoCs can use 4GiB DRAM chip, however their memory map
>> has only allocated 3GiB for DRAM, so only 3GiB of the DRAM is
>> accessible.
>
> How would that work in Linux?
>
>> Add a Kconfig option for the maximum accessible DRAM.
>>
>> For A80 it should be a much higher value (8GiB), but as I have no A80
>> device to test and originally U-Boot only supports 2GiB DRAM on A80, it
>> currently still falls under the 2GiB situation.
>
> I guess we have LPAE on armv7 to deal with this nicely.

AFAIK even though we do have LPAE, the hardware bus is not wired up
to take advantage of it. :(

ChenYu