linux-kernel - Re: [PATCH] platform/chrome: cros_ec_typec: allow deferred probe of switch handles

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Date:   Tue, 24 Jan 2023 14:18:02 +1100
From:   Victor Ding <victording@...gle.com>
To:     Prashant Malani <pmalani@...omium.org>
Cc:     linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev,
        gustavoars@...nel.org, heikki.krogerus@...ux.intel.com,
        dnojiri@...omium.org, dustin@...ett.net, lee.jones@...aro.org,
        tzungbi@...nel.org, groeck@...omium.org,
        gregkh@...uxfoundation.org, tinghan.shen@...iatek.com,
        sebastian.reichel@...labora.com, enric.balletbo@...labora.com,
        bleung@...omium.org
Subject: Re: [PATCH] platform/chrome: cros_ec_typec: allow deferred probe of
 switch handles

On Tue, Jan 24, 2023 at 11:43 AM Prashant Malani <pmalani@...omium.org> wrote:
>
> On Mon, Jan 23, 2023 at 1:36 AM Victor Ding <victording@...omium.org> wrote:
> >
> > `fwnode_typec_{retimer,mux,switch}_get()` could return `-EPROBE_DEFER`,
> > which is called from `cros_typec_get_switch_handles`. When this happens,
> > it does not indicate absence of switches; instead, it only hints that
> > probing of switches should occur at a later time.
> >
> > Progagate `-EPROBE_DEFER` to upper layer logic so that they can re-try
> > probing switches as a better time.
> >
> > Signed-off-by: Victor Ding <victording@...omium.org>
> > ---
> >
> >  drivers/platform/chrome/cros_ec_typec.c | 30 +++++++++++++++++--------
> >  1 file changed, 21 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> > index 59de4ce01fab..f4b3fc788491 100644
> > --- a/drivers/platform/chrome/cros_ec_typec.c
> > +++ b/drivers/platform/chrome/cros_ec_typec.c
> > @@ -145,31 +145,37 @@ static int cros_typec_get_switch_handles(struct cros_typec_port *port,
> >                                          struct fwnode_handle *fwnode,
> >                                          struct device *dev)
> >  {
> > +       int ret = 0;
> > +
> >         port->mux = fwnode_typec_mux_get(fwnode, NULL);
> >         if (IS_ERR(port->mux)) {
> > -               dev_dbg(dev, "Mux handle not found.\n");
> > +               ret = PTR_ERR(port->mux);
> > +               dev_dbg(dev, "Mux handle not found: %d.\n", ret);
> >                 goto mux_err;
> >         }
> >
> >         port->retimer = fwnode_typec_retimer_get(fwnode);
> >         if (IS_ERR(port->retimer)) {
> > -               dev_dbg(dev, "Retimer handle not found.\n");
> > +               ret = PTR_ERR(port->retimer);
> > +               dev_dbg(dev, "Retimer handle not found: %d.\n", ret);
> >                 goto retimer_sw_err;
> >         }
> >
> >         port->ori_sw = fwnode_typec_switch_get(fwnode);
> >         if (IS_ERR(port->ori_sw)) {
> > -               dev_dbg(dev, "Orientation switch handle not found.\n");
> > +               ret = PTR_ERR(port->ori_sw);
> > +               dev_dbg(dev, "Orientation switch handle not found: %d\n", ret);
> >                 goto ori_sw_err;
> >         }
> >
> >         port->role_sw = fwnode_usb_role_switch_get(fwnode);
> >         if (IS_ERR(port->role_sw)) {
> > -               dev_dbg(dev, "USB role switch handle not found.\n");
> > +               ret = PTR_ERR(port->role_sw);
> > +               dev_dbg(dev, "USB role switch handle not found: %d\n", ret);
> >                 goto role_sw_err;
> >         }
> >
> > -       return 0;
> > +       return ret;
> >
> >  role_sw_err:
> >         typec_switch_put(port->ori_sw);
> > @@ -181,7 +187,7 @@ static int cros_typec_get_switch_handles(struct cros_typec_port *port,
> >         typec_mux_put(port->mux);
> >         port->mux = NULL;
> >  mux_err:
> > -       return -ENODEV;
> > +       return ret;
> >  }
> >
> >  static int cros_typec_add_partner(struct cros_typec_data *typec, int port_num,
> > @@ -423,9 +429,15 @@ static int cros_typec_init_ports(struct cros_typec_data *typec)
> >                 }
> >
> >                 ret = cros_typec_get_switch_handles(cros_port, fwnode, dev);
> > -               if (ret)
> > -                       dev_dbg(dev, "No switch control for port %d\n",
> > -                               port_num);
> > +               switch (ret) {
> > +               case 0:
> > +                       break;
> > +               case -EPROBE_DEFER:
> > +                       dev_err(dev, "Deferring getting switch handles at port %d\n", port_num);
> > +                       goto unregister_ports;
> > +               default:
> > +                       dev_dbg(dev, "No switch control for port %d, err: %d\n", port_num, ret);
> > +               }
>
> The switch statement seems a little clunky here. Instead, nest a couple
> of ifs; it is shorter and easier to read IMO.
>
> ret = cros_typec_get_switch_handles(cros_port, fwnode, dev);
> if (ret) {
>     dev_err_probe(dev, ret, "No switch control for port: %d\n", port_num);
>     if (ret == -EPROBE_DEFER)
>         goto unregister_ports;
> }
>
Good idea, I'll update accordingly in the next revision.
> }
> }
> >
> >                 ret = cros_typec_register_port_altmodes(typec, port_num);
> >                 if (ret) {
> > --
> > 2.39.0.246.g2a6d74b583-goog
> >