[PATCH] Add a VMSPLIT_2G_OPT config option.

[Ard Biesheuvel]

(+ Russell, Arnd, Linus)

On Tue, 3 Nov 2020 at 22:52, Christian Melki <christian.melki at t2data.com> wrote:
>
> This allows 2GB systems to have their RAM entirely mapped as low memory.
> Needed to avoid CONFIG_HIGHMEM for the last 256M.
>
> Definitely not an uncommon configuration in the industry.
> Following the discussions about deprecating CONFIG_HIGHMEM down the
> line, this is probably a nice addition.
>
> Tested on a Kontron i.MX6 Quad board equipped with 2G RAM.
>
> Signed-off-by: Christian Melki <christian.melki at t2data.com>

Acked-by: Ard Biesheuvel <ardb at kernel.org>

> ---
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index fe2f17eb2b50..b86eab96fd58 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1311,6 +1311,9 @@ choice
>                 bool "3G/1G user/kernel split (for full 1G low memory)"
>         config VMSPLIT_2G
>                 bool "2G/2G user/kernel split"
> +       config VMSPLIT_2G_OPT
> +               depends on !ARM_LPAE
> +               bool "2G/2G user/kernel split (for full 2G low memory)"
>         config VMSPLIT_1G
>                 bool "1G/3G user/kernel split"
>   endchoice
> @@ -1319,6 +1322,7 @@ config PAGE_OFFSET
>         hex
>         default PHYS_OFFSET if !MMU
>         default 0x40000000 if VMSPLIT_1G
> +       default 0x70000000 if VMSPLIT_2G_OPT
>         default 0x80000000 if VMSPLIT_2G
>         default 0xB0000000 if VMSPLIT_3G_OPT
>         default 0xC0000000
> --
>
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