Re: [PATCH v4] arm64: dts: mediatek: mt7986a-bananapi-bpi-r3: add ramoops region

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] dts: ramoops misconfiguration wastes memory and contradicts commit intent
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commit 1ae7641b46f058deabfa7ee4bb83a27014f13e00
Author: Martino Dell'Ambrogio <tillo@tillo.ch>
Subject: arm64: dts: mediatek: mt7986a-bananapi-bpi-r3: add ramoops region

This commit reserves RAM for persistent kernel log storage via pstore/ramoops
to allow post-panic console output recovery after a warm reset. It intends to
reserve a 64 KiB carve-out just below the ARM Trusted Firmware secmon region.

Link: https://lore.kernel.org/all/20260915064302.1595204-1-tillo@tillo.ch/
Link: https://lore.kernel.org/all/20260528123655.2650868-1-tillo@tillo.ch/
Link: https://lore.kernel.org/all/20260528093038.1945245-1-tillo@tillo.ch/

> diff --git a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
> index 637e5567c1e08..150b794c2118d 100644
> --- a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
> +++ b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts

[ ... ]

> +	reserved-memory {
> +		ramoops@42f00000 {
> +			compatible = "ramoops";
> +			reg = <0 0x42f00000 0 0x100000>;
> +			no-map;
> +			record-size = <0x20000>;
> +			console-size = <0x40000>;
> +			ftrace-size = <0x10000>;
> +			pmsg-size = <0x10000>;

[Severity: Medium]
Does this block define sizes that mismatch the commit message intent?

The commit message explicitly claims to reserve exactly 64 KiB (0x10000) 
with zone sizes of 8 KiB, 32 KiB, 8 KiB, and 8 KiB.

However, the reg property here reserves 1 MiB (0x100000) instead of 64 KiB,
and the configured zone sizes sum to 512 KiB (0x80000). Because this region
has the no-map property, it unconditionally removes 1 MiB from the system 
memory map, wasting 960 KiB of usable RAM compared to the stated design.

Additionally, the requested sizes are scaled up (e.g., record-size is 
128 KiB / 0x20000 rather than 8 KiB / 0x2000), leaving the second half of 
the 1 MiB carve-out completely unused by ramoops.

> +			ecc-size = <16>;
> +		};
> +	};
>  };

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Sashiko AI review · https://sashiko.dev/#/patchset/20260915135727.567145-1-tillo@tillo.ch?part=1