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

From: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Thierry Reding <treding@nvidia.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Mathias Nyman <mathias.nyman@intel.com>,
	JC Kuo <jckuo@nvidia.com>, Nicolas Chauvet <kwizart@gmail.com>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-tegra@vger.kernel.org
Subject: Re: [PATCH v1] usb: xhci: tegra: Check padctrl interrupt presence in device tree
Date: Fri, 22 Oct 2021 11:29:11 +0200	[thread overview]
Message-ID: <YXKEZyweVxvNyl8K@qmqm.qmqm.pl> (raw)
In-Reply-To: <0a48c38e-1841-0dc9-473e-5dbe67ce04d5@gmail.com>

On Fri, Oct 22, 2021 at 08:58:02AM +0300, Dmitry Osipenko wrote:
> 22.10.2021 01:14, Michał Mirosław пишет:
> > On Fri, Oct 22, 2021 at 12:46:23AM +0300, Dmitry Osipenko wrote:
> >> 22.10.2021 00:37, Michał Mirosław пишет:
> >>> 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.
> >>> [...]
> >>>> --- 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")) {
> >>>
> >>> Does this catch "interrupts-extended"?
> >>
> >> No, Tegra doesn't use interrupts-extended.
> > 
> > I believe it is generic and equivalent to "interrupt-parent" +
> > "interrupts" properties, so people might as well put this in
> > the DT to save (or loose) a few bytes.
> > 
> > You could just check if of_irq_get() returned -EINVAL instead of
> > matching "interrupts" property.
> 
> It should be a bad idea to rely on -EINVAL since it's ambiguous error code.
> 
> Perhaps it's fine to assume that today of_irq_get() may only return
> -EINVAL in a case of a missing DT property, but then it should be two
> patches here:
> 
> 1. Use -EINVAL and backport this fix to stable kernel.
> 2. Change of_irq_get() to return -ENOENT for a missing property and
> change tegra_xusb_probe() accordingly.

I would love to see the part 2 done, but I'm afraid you will need to
change a lot of callsites before that can happen.

Best Regards
Michał Mirosław