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From:   Prashant Malani <pmalani@chromium.org>
Date:   Mon, 23 Jan 2023 16:43:23 -0800
Message-ID: <CACeCKafcL=KJ+a5C2BKXWX3rkWf9BHp1oB3dikAjGtFWqW5_PA@mail.gmail.com>
Subject: Re: [PATCH] platform/chrome: cros_ec_typec: allow deferred probe of
 switch handles
To:     Victor Ding <victording@chromium.org>
Cc:     linux-kernel@vger.kernel.org, chrome-platform@lists.linux.dev,
        gustavoars@kernel.org, heikki.krogerus@linux.intel.com,
        dnojiri@chromium.org, dustin@howett.net, lee.jones@linaro.org,
        tzungbi@kernel.org, groeck@chromium.org,
        gregkh@linuxfoundation.org, tinghan.shen@mediatek.com,
        sebastian.reichel@collabora.com, enric.balletbo@collabora.com,
        bleung@chromium.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Jan 23, 2023 at 1:36 AM Victor Ding <victording@chromium.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@chromium.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;
}

}
}
>
>                 ret = cros_typec_register_port_altmodes(typec, port_num);
>                 if (ret) {
> --
> 2.39.0.246.g2a6d74b583-goog
>