Re: [PATCH v30 7/7] arm64: dts: imx8ulp-evk: add reserved memory property

[Frieder Schrempf]

On 24.07.26 11:05, pankaj.gupta@xxxxxxxxxxx wrote:
> From: Pankaj Gupta <pankaj.gupta@xxxxxxx>
> 
> Reserve 1MB of DDR memory region due to EdgeLock Enclave's hardware
> limitation restricting access to DDR addresses from 0x80000000
> to 0xafffffff.
> 
> Signed-off-by: Pankaj Gupta <pankaj.gupta@xxxxxxx>
> Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
> ---
>  arch/arm64/boot/dts/freescale/imx8ulp-evk.dts | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/imx8ulp-evk.dts b/arch/arm64/boot/dts/freescale/imx8ulp-evk.dts
> index 5dea66c1e7aa..16399d921e04 100644
> --- a/arch/arm64/boot/dts/freescale/imx8ulp-evk.dts
> +++ b/arch/arm64/boot/dts/freescale/imx8ulp-evk.dts
> @@ -1,6 +1,6 @@
>  // SPDX-License-Identifier: (GPL-2.0+ OR MIT)
>  /*
> - * Copyright 2021 NXP
> + * Copyright 2021, 2025 NXP
>   */
>  
>  /dts-v1/;
> @@ -37,6 +37,12 @@ linux,cma {
>  			linux,cma-default;
>  		};
>  
> +		ele_reserved: memory@90000000 {
> +			compatible = "shared-dma-pool";
> +			reg = <0 0x90000000 0 0x100000>;

Instead of using a fixed address here, why not use 'alloc-ranges' to
specify a valid range and let the kernel decide on where to reserve the
1MB area?

As mentioned for the other patch, I would prefer a universal default for
the memory node in a dtsi that can be used by all imx8ulp boards. See
[1] for the i.MX93 proposal.

[1]
https://patchwork.kernel.org/project/linux-arm-kernel/patch/20260727-upstreaming-next-20260609-imx-ocotp-ele-v4-10-1a515de33093@xxxxxxxxxx/

> +			no-map;
> +		};
> +
>  		m33_reserved: noncacheable-section@a8600000 {
>  			reg = <0 0xa8600000 0 0x1000000>;
>  			no-map;
> @@ -259,6 +265,10 @@ &usdhc0 {
>  	status = "okay";
>  };
>  
> +&hsm0 {
> +	memory-region = <&ele_reserved>;
> +};
> +
>  &fec {
>  	pinctrl-names = "default", "sleep";
>  	pinctrl-0 = <&pinctrl_enet>;
>