Re: [PATCH v3 08/19] drm/bridge: inno-hdmi: Allow the register map to come from a parent

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Early HPD interrupt can cause a NULL pointer dereference of `hdmi->bridge.dev` if it fires before `drm_bridge_attach` completes.
--

commit 1a1229643b989df67626f64f580add186cebd6ed
Author: Michal Wilczynski <m.wilczynski@samsung.com>

drm/bridge: inno-hdmi: Allow the register map to come from a parent
    
On some SoCs the HDMI controller does not own its register window. The
StarFive JH7110 documents one 64 KB block, u0_hdmitx, that holds both
the controller and the PHY, so the parent device maps it and owns the
regmap while the two children share it.

> diff --git a/drivers/gpu/drm/bridge/inno-hdmi.c b/drivers/gpu/drm/bridge/inno-hdmi.c
> index aab474740f7f5..8bd7717611804 100644
> --- a/drivers/gpu/drm/bridge/inno-hdmi.c
> +++ b/drivers/gpu/drm/bridge/inno-hdmi.c
[ ... ]
> @@ -1095,9 +1110,19 @@ struct inno_hdmi *inno_hdmi_probe(struct platform_device *pdev,
>  	hdmi->dev = dev;
>  	hdmi->plat_data = plat_data;
>  
> -	hdmi->regs = devm_platform_ioremap_resource(pdev, 0);
> -	if (IS_ERR(hdmi->regs))
> -		return ERR_CAST(hdmi->regs);
> +	/*
> +	 * On platforms where the controller shares a register space with
> +	 * other blocks, the parent owns the regmap. Fall back to mapping
> +	 * our own resource where it does not.
> +	 */
> +	if (dev->parent)
> +		hdmi->regmap = dev_get_regmap(dev->parent, NULL);
> +
> +	if (!hdmi->regmap) {
> +		hdmi->regs = devm_platform_ioremap_resource(pdev, 0);
> +		if (IS_ERR(hdmi->regs))
> +			return ERR_CAST(hdmi->regs);
> +	}
>  
>  	hdmi->pclk = devm_clk_get_enabled(hdmi->dev, "pclk");
>  	if (IS_ERR(hdmi->pclk)) {

[Severity: High]
This is a pre-existing issue, but could this code trigger a NULL pointer
dereference if the hotplug interrupt fires early?

Looking at the rest of inno_hdmi_probe(), the hardware interrupt is unmuted
in inno_hdmi_init_hw(), and then the handler is registered:

    inno_hdmi_init_hw(hdmi);
    ...
    ret = devm_request_threaded_irq(dev, irq, inno_hdmi_hardirq,
                                    inno_hdmi_irq, IRQF_SHARED,
                                    dev_name(dev), hdmi);

If a cable is already connected or plugged in at this exact moment, the
interrupt can fire immediately. The threaded handler inno_hdmi_irq() will
then execute:

    drm_helper_hpd_irq_event(hdmi->bridge.dev);

However, hdmi->bridge.dev appears to be NULL at this point, as it is only
populated later when the upstream display controller calls
drm_bridge_attach().

Is there something preventing this race condition, or should the IRQ handler
registration be deferred?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260904-jh7110-clean-send-v3-0-484f9ae72715@samsung.com?part=8