On Tue, Dec 20, 2022 at 02:15:19PM +0000, Matthias Kaehlcke wrote:
> Hi Johan,
>
> On Tue, Dec 20, 2022 at 08:55:52AM +0100, Johan Hovold wrote:
> > On Tue, Dec 20, 2022 at 12:45:01AM +0000, Matthias Kaehlcke wrote:
> > > Some boards have device tree nodes for USB hubs supported by the
> > > onboard_usb_hub driver, but the nodes don't have all properties
> > > needed for the driver to work properly (which is not necessarily
> > > an error in the DT). Currently _find_onboard_hub() returns
> > > -EPROBE_DEFER in such cases, which results in an unusable USB hub,
> > > since successive probes fail in the same way. Use the absence of
> > > the "vdd" supply as an indicator of such 'incomplete' DT nodes
> > > and return -ENODEV.
> > >
> > > Fixes: 8bc063641ceb ("usb: misc: Add onboard_usb_hub driver")
> > > Reported-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
> > > Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> > > ---
> > >
> > > drivers/usb/misc/onboard_usb_hub.c | 9 +++++++++
> > > 1 file changed, 9 insertions(+)
> > >
> > > diff --git a/drivers/usb/misc/onboard_usb_hub.c b/drivers/usb/misc/onboard_usb_hub.c
> > > index d63c63942af1..2968da515016 100644
> > > --- a/drivers/usb/misc/onboard_usb_hub.c
> > > +++ b/drivers/usb/misc/onboard_usb_hub.c
> > > @@ -363,6 +363,15 @@ static struct onboard_hub *_find_onboard_hub(struct device *dev)
> > > hub = dev_get_drvdata(&pdev->dev);
> > > put_device(&pdev->dev);
> > >
> > > + /*
> > > + * Some boards have device tree nodes for USB hubs supported by this
> > > + * driver, but the nodes don't have all properties needed for the driver
> > > + * to work properly. Use the absence of the "vdd" supply as an indicator
> > > + * of such nodes.
> > > + */
> > > + if (!of_get_property(pdev->dev.of_node, "vdd", NULL))
> > > + return ERR_PTR(-ENODEV);
> >
> > Does this not break your original use case? Don't you want "vdd-supply"
> > here?
>
> Ouch, yes it does (to a certain degree). Thanks for pointing it out. My
> sanity check didn't catch this because the platform driver still probes
> successfully and powers the hub on.
>
> > That said, this seems like the wrong property to look for both in
> > principle and as it is described as optional by the binding:
> >
> > Documentation/devicetree/bindings/usb/realtek,rts5411.yaml
> >
> > It seems that you should use the compatible property and check that it
> > holds one of the expected values:
> >
> > - usbbda,5411
> > - usbbda,411
> >
> > rather than treat every hub node as describing a realtek hub (AFAIK,
> > there is no generic binding for this yet).
>
> The driver only probes for specific hub models, among them the Microchip
> USB2514B hub with which Stefan encountered the regression [1].
>
> My initial assumption when writing this driver was that the existence of
> a node for a supported hub means that the driver should be used. However
> the regression encountered by Stefan makes clear that this assumption is
> incorrect. It's not common, but a device tree may have nodes for onboard
> USB devices, among them hubs (which might become more common with this
> driver). Not in all instances the hub nodes were added with the intention
> of using this driver for power sequencing the hub (e.g. [2]).
Yeah, you can't assume that. The DT bindings for USB has been around
since before your onboard-hub driver.
> The
> compatible string alone doesn't indicate that the onboard_hub driver
> should be instantiated for a given hub, which is why I'm using the
> existence of "vdd-supply" as indicator.
I don't have time to review this in details, but checking for a specific
supply like this just seems wrong (as other have since also pointed out
in comments to your v2). There could be hubs which just need to deassert
a reset pin for example, and some of the bindings do not even mandate a
regulator as I mentioned above.
Johan
