Re: [PATCH v9 05/13] drm/mediatek: mtk_dsi: Enable interrupt at component bind time

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/mediatek: mtk_dsi: IRQ enablement in bind leaves hardware unclocked
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commit 341145986d590feda3b9b8dd572d45aaa3bc1404
Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

drm/mediatek: mtk_dsi: Enable interrupt at component bind time

This patch changes the DSI interrupt to be requested with IRQF_NO_AUTOEN
during probe, deferring its enablement to the component bind phase.
It aims to prevent interrupt storms or premature hardware resets before
the display controller is fully bound and ready.

> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 28ba532210ff5..6ac6daa61e684 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
[ ... ]
> @@ -1101,6 +1102,8 @@ static int mtk_dsi_bind(struct device *dev, struct device *master, void *data)
>  		return ret;
>  	}
>  
> +	enable_irq(dsi->irq);

[Severity: High]
Does enabling the IRQ here leave the hardware vulnerable to unclocked MMIO
reads if an interrupt fires before power-on?

The hardware clocks (engine_clk, digital_clk) are not enabled until
mtk_dsi_poweron() is called. If an interrupt fires immediately after this
enable_irq() call, or during any power-off state where mtk_dsi_poweroff() has
been called (since disable_irq() is only in mtk_dsi_unbind()), the interrupt
handler mtk_dsi_irq() will execute:

mtk_dsi_irq() {
    ...
    status = readl(dsi->regs + DSI_INTSTA) & flag;
    ...
}

On MediaTek SoCs, reading unclocked APB/AHB registers like DSI_INTSTA can
cause a bus hang resulting in a synchronous external abort (kernel panic).

Could this happen consistently if the bootloader asserts the interrupt, or
randomly during suspend/DPMS off if a spurious interrupt occurs?

> +
>  	return 0;
>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/20260916110825.102631-1-angelogioacchino.delregno@collabora.com?part=5