Re: [PATCH v3 09/19] drm/bridge: inno-hdmi: Add .disable platform operation

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Hardware Teardown Order Inversion Risking MMIO Aborts
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commit 3edb8b3d87e91fedec7589ce07bc351965b21765
Author: Michal Wilczynski <m.wilczynski@samsung.com>

drm/bridge: inno-hdmi: Add .disable platform operation

This commit adds a new .disable platform operation to the Innosilicon HDMI
driver to support platform-specific power down sequences. The new callback
is executed during the bridge's atomic disable phase.

> diff --git a/drivers/gpu/drm/bridge/inno-hdmi.c b/drivers/gpu/drm/bridge/inno-hdmi.c
> --- a/drivers/gpu/drm/bridge/inno-hdmi.c
> +++ b/drivers/gpu/drm/bridge/inno-hdmi.c
[ ... ]
> @@ -886,6 +886,10 @@ static void inno_hdmi_bridge_atomic_disable(struct drm_bridge *bridge,
>  					    struct drm_atomic_commit *state)
>  {
>  	struct inno_hdmi *hdmi = bridge_to_inno_hdmi(bridge);
> +	const struct inno_hdmi_plat_ops *plat_ops = hdmi->plat_data->ops;
> +
> +	if (plat_ops && plat_ops->disable)
> +		plat_ops->disable(hdmi->dev);
>  
>  	inno_hdmi_standby(hdmi);

[Severity: High]
Does calling the platform disable callback before inno_hdmi_standby() risk
MMIO aborts?

The platform disable hook (such as the JH7110 implementation mentioned in the
commit message) typically powers off the PHY and disables clocks. However,
inno_hdmi_standby() attempts to perform MMIO writes to PHY registers like
HDMI_PHY_DRIVER and HDMI_PHY_PRE_EMPHASIS.

Accessing hardware registers after the PHY has been powered off and clocks
disabled can cause a synchronous external abort (bus hang) or silent
failures on many SoC architectures.

Since plat_ops->enable() is called prior to configuring the PHY registers
during setup, should the teardown follow a strict LIFO order where
inno_hdmi_standby() is called before plat_ops->disable()?

>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/20260904-jh7110-clean-send-v3-0-484f9ae72715@samsung.com?part=9