Re: [PATCH v2] dma-direct: set decrypted flag for remapped DMA allocations

["Arnd Bergmann" <arnd@kernel.org>]

On Wed, Jan 7, 2026, at 18:41, Linus Walleij wrote:
> I did a grep 'alloc-ranges' but now I'm a bit slow in the head
> so cannot really figure out if these will end up outside the
> linear map or not.

The way I see it, we have two ways of doing it:

1GB of RAM, CMA in the last 256MB:
arch/arm/boot/dts/nvidia/tegra20-acer-a500-picasso.dts:
        memory@0 {
                reg = <0x00000000 0x40000000>;
        };
        reserved-memory {
                #address-cells = <1>;
                #size-cells = <1>;
                ranges;
                linux,cma@30000000 {
                        compatible = "shared-dma-pool";
                        alloc-ranges = <0x30000000 0x10000000>;
                        size = <0x10000000>; /* 256MiB */
                        linux,cma-default;
                        reusable;
                };
        };

2GB of RAM, CMA in the first 768MB:
arch/arm/boot/dts/nvidia/tegra30-asus-p1801-t.dts
        memory@80000000 {
                reg = <0x80000000 0x80000000>;
        };
        reserved-memory {
                #address-cells = <1>;
                #size-cells = <1>;
                ranges;
                linux,cma@80000000 {
                        compatible = "shared-dma-pool";
                        alloc-ranges = <0x80000000 0x30000000>;
                        size = <0x10000000>;            /* 256MiB */
                        linux,cma-default;
                        reusable;
                };
         };

With CONFIG_VMSPLIT_3G, the first example spans all of highmem,
i.e. 0x30000000-0x3fffffff, the second example spans all of
lowmem at 0x80000000-0xafffffff.

      Arnd