Re: [PATCH v4 3/7] arm64: dts: ti: k3-j7200-ti-ipc-firmware: Reserve memory for LPM metadata

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] dt-bindings: ABI break: appending firewalled lpm_memory_region to memory-region array crashes older kernels
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commit 07681f0176ba38c8ed49ce9e6c61d2f4b216437d
Author: Richard Genoud (TI) <richard.genoud@bootlin.com>

arm64: dts: ti: k3-j7200-ti-ipc-firmware: Reserve memory for LPM metadata

This commit declares a carveout memory region on J7200 to store LPM metadata,
which is needed for saving ATF context and certificate information. It also
appends this region to the mcu_r5fss0_core0 memory-region list.

> diff --git a/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi b/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi
> index d65f68c7d4321..a6043970715ac 100644
> --- a/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi
> +++ b/arch/arm64/boot/dts/ti/k3-j7200-ti-ipc-firmware.dtsi

[ ... ]

> @@ -99,8 +105,10 @@ &mcu_r5fss0 {
>  &mcu_r5fss0_core0 {
>  	mboxes = <&mailbox0_cluster0 &mbox_mcu_r5fss0_core0>;
>  	memory-region = <&mcu_r5fss0_core0_dma_memory_region>,
> -			<&mcu_r5fss0_core0_memory_region>;
> -	memory-region-names = "dma", "firmware";
> +			<&mcu_r5fss0_core0_memory_region>,
> +			<&lpm_memory_region>;
> +	memory-region-names = "dma", "firmware", "lpm-metadata";

[Severity: High]
Does appending the firewalled lpm_memory_region to the standard memory-region
array break Device Tree forward compatibility with older kernels?

Older kernel remoteproc drivers unconditionally iterate over all memory-region
elements (skipping index 0) and map them using devm_ioremap_resource_wc():

drivers/remoteproc/ti_k3_common.c:k3_reserved_mem_init() {
    ...
    kproc->rmem[j].cpu_addr = devm_ioremap_resource_wc(dev, &res);
    ...
}

Since the region is firewalled by TIFS and mapped as Write-Combine (Normal
Non-Cacheable memory), could speculative fetches to this memory trigger bus
errors (SError) and crash the system?

To maintain compatibility when running a new Device Tree on an older kernel,
should the firewalled region be provided via a custom property (e.g.,
ti,lpm-metadata) rather than overloading the standard memory-region array?

> +	bootph-pre-ram;
>  	status = "okay";
>  };

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260921145325.300025-1-richard.genoud@bootlin.com?part=3