Re: [PATCH v1] usb: xhci: tegra: Check padctrl interrupt presence in device tree

[Thierry Reding <thierry.reding@gmail.com>]

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On Thu, Oct 21, 2021 at 02:55:01PM +0300, Dmitry Osipenko wrote:
> Older device-trees don't specify padctrl interrupt and xhci-tegra driver
> now fails to probe with -EINVAL using those device-trees. Check interrupt
> presence and disallow runtime PM suspension if it's missing to fix the
> trouble.
> 
> Fixes: 971ee247060d ("usb: xhci: tegra: Enable ELPG for runtime/system PM")
> Reported-by: Nicolas Chauvet <kwizart@gmail.com>
> Tested-by: Nicolas Chauvet <kwizart@gmail.com>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/usb/host/xhci-tegra.c | 32 +++++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 11 deletions(-)

Thanks for typing this up. A couple of minor comments below.

> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
> index 1bf494b649bd..47927a1df3dc 100644
> --- a/drivers/usb/host/xhci-tegra.c
> +++ b/drivers/usb/host/xhci-tegra.c
> @@ -1454,10 +1454,13 @@ static int tegra_xusb_probe(struct platform_device *pdev)
>  		goto put_padctl;
>  	}
>  
> -	tegra->padctl_irq = of_irq_get(np, 0);
> -	if (tegra->padctl_irq <= 0) {
> -		err = (tegra->padctl_irq == 0) ? -ENODEV : tegra->padctl_irq;
> -		goto put_padctl;
> +	/* Older device-trees don't specify padctrl interrupt */
> +	if (of_property_read_bool(np, "interrupts")) {

Can't we just rely on the return value from of_irq_get() instead of
explicitly checking for the presence of the "interrupts" property? All
we really want is to make this interrupt optional. As far as I can tell,
of_irq_get() will return -EINVAL (via of_irq_parse_one() and then
of_property_read_u32_index()) if the property doesn't exist, so I'd
think it should be possible to turn this into something like this:

	tegra->padctl_irq = of_irq_get(np, 0);
	if (tegra->padctl_irq == -EINVAL)
		tegra->padctl_irq = 0;

> +		tegra->padctl_irq = of_irq_get(np, 0);
> +		if (tegra->padctl_irq <= 0) {
> +			err = (tegra->padctl_irq == 0) ? -ENODEV : tegra->padctl_irq;
> +			goto put_padctl;
> +		}
>  	}
>  
>  	tegra->host_clk = devm_clk_get(&pdev->dev, "xusb_host");
> @@ -1696,11 +1699,15 @@ static int tegra_xusb_probe(struct platform_device *pdev)
>  		goto remove_usb3;
>  	}
>  
> -	err = devm_request_threaded_irq(&pdev->dev, tegra->padctl_irq, NULL, tegra_xusb_padctl_irq,
> -					IRQF_ONESHOT, dev_name(&pdev->dev), tegra);
> -	if (err < 0) {
> -		dev_err(&pdev->dev, "failed to request padctl IRQ: %d\n", err);
> -		goto remove_usb3;
> +	if (tegra->padctl_irq) {
> +		err = devm_request_threaded_irq(&pdev->dev, tegra->padctl_irq,
> +						NULL, tegra_xusb_padctl_irq,
> +						IRQF_ONESHOT, dev_name(&pdev->dev),
> +						tegra);
> +		if (err < 0) {
> +			dev_err(&pdev->dev, "failed to request padctl IRQ: %d\n", err);
> +			goto remove_usb3;
> +		}
>  	}
>  
>  	err = tegra_xusb_enable_firmware_messages(tegra);
> @@ -2132,7 +2139,7 @@ static __maybe_unused int tegra_xusb_suspend(struct device *dev)
>  		tegra->suspended = true;
>  		pm_runtime_disable(dev);
>  
> -		if (device_may_wakeup(dev)) {
> +		if (device_may_wakeup(dev) && tegra->padctl_irq) {

I wondered if perhaps there was a way to make device_may_wakeup() return
false if we don't have that IRQ. Intuitively I would've thought that the
calls to device_wakeup_enable() and device_init_wakeup() set this all up
but after looking at the code I'm not sure if omitting them would
actually cause device_may_wakeup() to return false. That would certainly
be nicer than these double checks.

>  			if (enable_irq_wake(tegra->padctl_irq))
>  				dev_err(dev, "failed to enable padctl wakes\n");
>  		}
> @@ -2161,7 +2168,7 @@ static __maybe_unused int tegra_xusb_resume(struct device *dev)
>  		return err;
>  	}
>  
> -	if (device_may_wakeup(dev)) {
> +	if (device_may_wakeup(dev) && tegra->padctl_irq) {
>  		if (disable_irq_wake(tegra->padctl_irq))
>  			dev_err(dev, "failed to disable padctl wakes\n");
>  	}
> @@ -2179,6 +2186,9 @@ static __maybe_unused int tegra_xusb_runtime_suspend(struct device *dev)
>  	struct tegra_xusb *tegra = dev_get_drvdata(dev);
>  	int ret;
>  
> +	if (!tegra->padctl_irq)
> +		return -EOPNOTSUPP;
> +

Similarly, couldn't we enable all that runtime PM stuff conditionally so
that these functions would only ever get called when runtime PM is
actually available? That seems a bit nicer than having this return
-EOPNOTSUPP.

Thierry

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