Re: [PATCH] arm64: dts: renesas: ironhide: Describe inline ECC carveouts

[Geert Uytterhoeven]

Hi Marek,

On Fri, 10 Jul 2026 at 00:12, Marek Vasut
<marek.vasut+renesas@xxxxxxxxxxx> wrote:
> The DBSC5 DRAM controller protects DRAM content using inline ECC.
> The inline ECC utilizes areas of DRAM for its operation, which are
> in the DRAM address range, but must not be accessed or modified.
> Describe the inline ECC carveout areas used by the DBSC5 controller
> on this hardware as reserved-memory, which must not be accessed.
>
> In case of high DRAM utilization, unless the inline ECC carveouts
> are properly reserved, Linux may use and corrupt the memory used
> by the DBSC5 DRAM controller for inline ECC, which would lead to
> the system becoming unstable.
>
> Fixes: ad142a4ef710 ("arm64: dts: renesas: r8a78000: Add initial Ironhide board support")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxxxx>

Thanks for your patch!

> --- a/arch/arm64/boot/dts/renesas/r8a78000-ironhide.dts
> +++ b/arch/arm64/boot/dts/renesas/r8a78000-ironhide.dts
> @@ -107,6 +107,47 @@ tee@8c400000 {
>                         reg = <0x0 0x8c400000 0x0 0x02000000>;
>                         no-map;
>                 };
> +
> +               /* DRAM controller inline ECC areas */
> +               ecc@10cccd0000 {
> +                       reg = <0x10 0xcccd0000 0x0 0x33330000>;

I think you do want to include the 64 KiB block of unprotected RAM in
each region, e.g.

    reg = <0x10 0xcccc0000 0x0 0x33340000>;

While that block is usable, it is not protected by ECC, and thus can
be subject to unnoticed corruption.

Alternatively, you could put these in separate reserved regions, to
make it easier for users to re-enable them if they don't care. But
those users might want to disable ECC completely (is that possible?),
again suggesting to keep them together.

> +                       no-map;
> +               };

The rest LGTM.

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds