Re: [PATCH v6 2/7] platform/chrome: cros_ec_typec: Purge blocking switch devlinks

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Nov 24, 2022 at 06:20:51PM +0800, Pin-yen Lin wrote:
> From: Prashant Malani <pmalani@chromium.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.

...

> +	/*
> +	 * 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).
> +	 */

A bit too long lines...

> +	if (dev->of_node)

Why do you need this check?

> +		device_for_each_child_node(dev, fwnode)
> +			fw_devlink_purge_absent_suppliers(fwnode);

-- 
With Best Regards,
Andy Shevchenko