> From: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> Sent: Wednesday, April 13, 2022 4:10 PM
> To: Linyu Yuan (QUIC) <quic_linyyuan@xxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; linux-
> usb@xxxxxxxxxxxxxxx; Jack Pham (QUIC) <quic_jackp@xxxxxxxxxxx>
> Subject: Re: [PATCH 3/3] usb: typec: ucsi: retry find role swithch when
> module load late
>
> On Wed, Apr 13, 2022 at 08:00:35AM +0000, Linyu Yuan (QUIC) wrote:
> > > From: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > > Sent: Wednesday, April 13, 2022 3:46 PM
> > > To: Linyu Yuan (QUIC) <quic_linyyuan@xxxxxxxxxxx>
> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; linux-
> > > usb@xxxxxxxxxxxxxxx; Jack Pham (QUIC) <quic_jackp@xxxxxxxxxxx>
> > > Subject: Re: [PATCH 3/3] usb: typec: ucsi: retry find role swithch when
> > > module load late
> > >
> > > On Tue, Apr 12, 2022 at 06:30:07PM +0800, Linyu Yuan wrote:
> > > > When role switch enabled, return -EAGAIN if fail to find it due to
> > > > module load ordering issue, then restart ucsi init work to find
> > > > it again every 100ms.
> > > >
> > > > It also means change ucsi init work to delayed_work.
> > > >
> > > > Signed-off-by: Linyu Yuan <quic_linyyuan@xxxxxxxxxxx>
> > > > ---
> > > > drivers/usb/typec/ucsi/ucsi.c | 28 ++++++++++++++++------------
> > > > drivers/usb/typec/ucsi/ucsi.h | 2 +-
> > > > 2 files changed, 17 insertions(+), 13 deletions(-)
> > > >
> > > > diff --git a/drivers/usb/typec/ucsi/ucsi.c
> b/drivers/usb/typec/ucsi/ucsi.c
> > > > index 684fc4f..fabd4df 100644
> > > > --- a/drivers/usb/typec/ucsi/ucsi.c
> > > > +++ b/drivers/usb/typec/ucsi/ucsi.c
> > > > @@ -1053,6 +1053,14 @@ static int ucsi_register_port(struct ucsi *ucsi,
> int
> > > index)
> > > > con->num = index + 1;
> > > > con->ucsi = ucsi;
> > > >
> > > > + cap->fwnode = ucsi_find_fwnode(con);
> > > > + con->usb_role_sw = fwnode_usb_role_switch_get(cap->fwnode);
> > > > + if (IS_ERR(con->usb_role_sw)) {
> > > > + dev_err(ucsi->dev, "con%d: failed to get usb role switch\n",
> > > > + index + 1);
> > > > + return -EAGAIN;
> > > > + }
> > >
> > > No, this is wrong. If there is a role switch assigned in the firmware
> > > for the port, then fwnode_usb_role_switch_get() will return
> > > -EPROBE_DEFER until the switch has been registered.
> > >
> > > So I think what you want to do is just make the failure to get the
> > > role switch fatal in this driver. Just return PTR_ERR(con->usb_role_sw).
> > Thanks, will change it to check -EPROBE_DEFER.
>
> No, you don't check that, you just return that.
Yes, I do like it.
>
> So you don't need that crazy polling mechanism where you queue a work
> until you get the resource. Just let the driver core handle the
> situation.
The issue is when a UCSI implementation driver probe, it call ucsi_register(),
But this function will not return -EPROBE_DEFER,
It just queue a work to start connector discovery.
>
> thanks,
>
> --
> heikki
