linux-kernel - Re: [PATCH v2] usb: typec: tipd: Don't block probing of consumer of "connector" nodes

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Date:   Tue, 26 Jul 2022 10:44:49 +0200
From:   Martin Kepplinger <martin.kepplinger@...i.sm>
To:     Saravana Kannan <saravanak@...gle.com>,
        Angus Ainslie <angus.ainslie@...i.sm>
Cc:     grandmaster@...klimov.de, gregkh@...uxfoundation.org,
        heikki.krogerus@...ux.intel.com, rjw@...ysocki.net, kernel@...i.sm,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH v2] usb: typec: tipd: Don't block probing of consumer of
 "connector" nodes

Am Donnerstag, dem 21.07.2022 um 16:06 -0700 schrieb Saravana Kannan:
> On Tue, Jul 13, 2021 at 11:18 PM Martin Kepplinger
> <martin.kepplinger@...i.sm> wrote:
> > 
> > Similar as with tcpm this patch lets fw_devlink know not to wait on
> > the
> > fwnode to be populated as a struct device.
> > 
> > Without this patch, USB functionality can be broken on some
> > previously
> > supported boards.
> > 
> > Fixes: 28ec344bb891 ("usb: typec: tcpm: Don't block probing of
> > consumers of "connector" nodes")
> > Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
> > ---
> > 
> > revision history
> > ----------------
> > v2: (thank you Saravana)
> > * add a code-comment why the call is needed.
> > 
> > v1:
> > https://lore.kernel.org/linux-usb/20210713073946.102501-1-martin.kepplinger@puri.sm/
> > 
> > 
> > 
> >  drivers/usb/typec/tipd/core.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/drivers/usb/typec/tipd/core.c
> > b/drivers/usb/typec/tipd/core.c
> > index 938219bc1b4b..21b3ae25c76d 100644
> > --- a/drivers/usb/typec/tipd/core.c
> > +++ b/drivers/usb/typec/tipd/core.c
> > @@ -629,6 +629,15 @@ static int tps6598x_probe(struct i2c_client
> > *client)
> >         if (!fwnode)
> >                 return -ENODEV;
> > 
> > +       /*
> > +        * This fwnode has a "compatible" property, but is never
> > populated as a
> > +        * struct device. Instead we simply parse it to read the
> > properties.
> > +        * This breaks fw_devlink=on. To maintain backward
> > compatibility
> > +        * with existing DT files, we work around this by deleting
> > any
> > +        * fwnode_links to/from this fwnode.
> > +        */
> > +       fw_devlink_purge_absent_suppliers(fwnode);
> > +
> 
> Hey Martin,
> 
> As part of a series I'm working on, I'm looking into deleting
> fw_devlink_purge_absent_suppliers() and having the driver core figure
> this out automatically.
> 
> So I was making sure all the current uses of
> fw_devlink_purge_absent_suppliers() would automatically be handled by
> driver core. But when I looked at this usage of
> fw_devlink_purge_absent_suppliers(), I didn't see any "compatible"
> property in the "connector" child node. So, I'm confused how you had
> a
> problem without this patch.
> 
> fw_devlink would have created fwnode links
> between typec_pd and usb_dwc3_0, figured out it's a cycle and have
> stopped enforcing the "remote-endpoint" dependencies.
> 
> Can you give me more details please on why you were having a problem
> without this patch?
> 
> I'm looking at arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi as
> an
> example because you listed it in your v1 patch.
> 
> -Saravana

It's downstream. I'm very sorry about that. The patch that adds the
compatible string (
https://source.puri.sm/martin.kepplinger/linux-next/-/commit/3d887ea76158851ae50f192094d7865cc3f4da9d
) sits in our tree (
https://source.puri.sm/martin.kepplinger/linux-next/-/commits/5.19-rc7/librem5__integration
) and I'll make sure it'll be sent out after I'm back from vacations in
a few weeks.

Sorry for the confusion!

                             martin


> 
> >         tps->role_sw = fwnode_usb_role_switch_get(fwnode);
> >         if (IS_ERR(tps->role_sw)) {
> >                 ret = PTR_ERR(tps->role_sw);
> > --
> > 2.30.2
> >