linux-kernel - Re: [PATCH v7 2/9] platform/chrome: cros_ec

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Message-ID: <CAEXTbpcwKnMQ1=D940bf2GUNdK3K+-bhnOs2r5fwuTW+ozQajA@mail.gmail.com>
Date:   Sat, 7 Jan 2023 16:57:36 +0800
From:   Pin-yen Lin <treapking@...omium.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Prashant Malani <pmalani@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Xin Ji <xji@...logixsemi.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        linux-kernel@...r.kernel.org, Allen Chen <allen.chen@....com.tw>,
        linux-acpi@...r.kernel.org, Lyude Paul <lyude@...hat.com>,
        dri-devel@...ts.freedesktop.org, chrome-platform@...ts.linux.dev,
        Javier Martinez Canillas <javierm@...hat.com>,
        Marek Vasut <marex@...x.de>, devicetree@...r.kernel.org,
        Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCH v7 2/9] platform/chrome: cros_ec_typec: Purge blocking
 switch devlinks

Hi Andy,

Thanks for the review.

On Thu, Jan 5, 2023 at 11:34 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Thu, Jan 05, 2023 at 09:24:50PM +0800, Pin-yen Lin wrote:
> > From: Prashant Malani <pmalani@...omium.org>
> >
> > When using OF graph, the fw_devlink code will create links between the
> > individual port driver (cros-ec-typec here) and the parent device for
> > a Type-C switch (like mode-switch). Since the mode-switch will in turn
> > have the usb-c-connector (i.e the child of the port driver) as a
> > supplier, fw_devlink will not be able to resolve the cyclic dependency
> > correctly.
> >
> > As a result, the mode-switch driver probe() never runs, so mode-switches
> > are never registered. Because of that, the port driver probe constantly
> > fails with -EPROBE_DEFER, because the Type-C connector class requires all
> > switch devices to be registered prior to port registration.
> >
> > To break this deadlock and allow the mode-switch registration to occur,
> > purge all the usb-c-connector nodes' absent suppliers. This eliminates
> > the connector as a supplier for a switch and allows it to be probed.
>
> > Signed-off-by: Prashant Malani <pmalani@...omium.org>
> >
> > Signed-off-by: Pin-yen Lin <treapking@...omium.org>
>
> Tag block mustn't have the blank line(s).
>
> ...
>
> > +     /*
> > +      * OF graph may have set up some device links with switches, since
> > +      * connectors have their own compatible. Purge these to avoid a deadlock
> > +      * in switch probe (the switch mistakenly assumes the connector is a
> > +      * supplier).
> > +      */
>
> Perhaps even
>
>         /*
>          * OF graph may have set up some device links with switches,
>          * since connectors have their own compatible. Purge these
>          * to avoid a deadlock in switch probe (the switch mistakenly
>          * assumes the connector is a supplier).
>          */
>
> ?
I can update this in v8, though I wonder why shorter comments are
preferred as they haven't exceeded the 80-character length
requirement.
>
> > +     if (dev->of_node)
>
> I would use if (dev_of_node(dev)), but it's up to you and maintainers.

dev_of_node looks a bit better as it checks the enabled config for us.
I'll update this in v8.

>
> > +             device_for_each_child_node(dev, fwnode)
> > +                     fw_devlink_purge_absent_suppliers(fwnode);
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Best regards,
Pin-yen