Re: [PATCH v2 3/4] pmdomain: mediatek: mt8188: Enable the GPU timestamp counter

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] dt-bindings: ABI breakage for MT8188 older kernels via access-controllers
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commit 67ac5bbd1956b4f1ebf5fa4f2f96f5fd7b231689
Author: Michał Kopeć <michal@nozomi.space>

pmdomain: mediatek: mt8188: Enable the GPU timestamp counter

This commit adds MFGCFG as a second MT8188 access controller to maintain the
GPU timestamp counter. The counter loses its SoC system timer configuration
when the MFG1 power domain is turned off. Setting these bits when MFG1 is
powered on fixes always-zero timestamps for GPU jobs.

> diff --git a/drivers/pmdomain/mediatek/mt8188-pm-domains.h b/drivers/pmdomain/mediatek/mt8188-pm-domains.h
> index 3a989e83e9b79..88035cc6a808b 100644
> --- a/drivers/pmdomain/mediatek/mt8188-pm-domains.h
> +++ b/drivers/pmdomain/mediatek/mt8188-pm-domains.h
> @@ -14,8 +14,21 @@
>   * MT8188 power domain support
>   */
>  
> +#define MT8188_MFG_TIMESTAMP			0x130
> +#define MT8188_MFG_TIMESTAMP_EN			GENMASK(1, 0)
> +
>  static enum scpsys_bus_prot_block scpsys_bus_prot_blocks_mt8188[] = {
> -	BUS_PROT_BLOCK_INFRA
> +	BUS_PROT_BLOCK_INFRA, BUS_PROT_BLOCK_MFGCFG
>  };

[Severity: High]
Can adding a second bus protection block cause a regression on older kernels?

Older kernels hardcode soc->num_bus_prot_blocks to 1 for MT8188. If they boot
with an updated device tree containing two access-controllers handles,
scpsys_get_bus_protection() will fail because of its strict equality check:

drivers/pmdomain/mediatek/mtk-pm-domains.c:scpsys_get_bus_protection() {
    ...
    num_handles = of_count_phandle_with_args(np, "access-controllers", NULL);
    if (num_handles < 0 || num_handles != soc->num_bus_prot_blocks)
        return dev_err_probe(dev, -EINVAL,
                             "Cannot get access controllers: expected %u, got %d\n",
                             soc->num_bus_prot_blocks, num_handles);
    ...
}

Will this strict check return -EINVAL and prevent power domain initialization
entirely?

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Sashiko AI review · https://sashiko.dev/#/patchset/20261011184755.2058017-1-michal@nozomi.space?part=3