Re: [PATCH v7 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:

Pre-existing issues:
- [High] The DSI interrupt is enabled before hardware clocks are turned on, leaving the system vulnerable to a kernel panic or interrupt storm from unclocked register access.
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commit c2f480f41de24a194e9b0ecae5811e54e2bf871e
Author: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

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

This commit requests the DSI interrupt with IRQF_NO_AUTOEN to prevent it
from firing prematurely during probe. It explicitly enables the interrupt
during component bind and disables it during unbind instead.

> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 0b167b4411e59..ef1638e77f00e 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]
This isn't a bug introduced by this patch, but does this leave the system
vulnerable to a kernel panic or interrupt storm from unclocked register
accesses?

By enabling the interrupt here at the GIC level before the hardware clocks
are actually enabled in mtk_dsi_poweron(), the mtk_dsi_irq() handler can be
invoked while clocks are off. The handler in
drivers/gpu/drm/mediatek/mtk_dsi.c unconditionally accesses DSI_INTSTA:

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

If a spurious interrupt or a delayed bootloader interrupt fires between
mtk_dsi_bind() and mtk_dsi_poweron(), or indefinitely after the display is
disabled via mtk_dsi_poweroff() (which disables clocks but does not disable
the IRQ), the handler will execute while clocks are off. Accessing hardware
registers while clocks are disabled can cause a synchronous external abort.

>  	return 0;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260914115812.22751-1-angelogioacchino.delregno@collabora.com?part=5