Re: [PATCH v10 2/9] platform/chrome: cros_ec_typec: Purge blocking switch devlinks

[Heikki Krogerus]

On Thu, Jan 12, 2023 at 12:20:57PM +0800, Pin-yen Lin wrote:
> From: Prashant Malani <pmalani@xxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxx>
> Signed-off-by: Pin-yen Lin <treapking@xxxxxxxxxxxx>
> Reviewed-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
> Tested-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>

FWIW:

Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>

> ---
> 
> Changes in v10:
> - Collected Reviewed-by and Tested-by tags
> 
> Changes in v7:
> - Fix the long comment lines
> 
> Changes in v6:
> - New in v6
> 
>  drivers/platform/chrome/cros_ec_typec.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index 2a7ff14dc37e..302474a647cc 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -382,6 +382,16 @@ static int cros_typec_init_ports(struct cros_typec_data *typec)
>  		return -EINVAL;
>  	}
>  
> +	/*
> +	 * 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).
> +	 */
> +	if (dev_of_node(dev))
> +		device_for_each_child_node(dev, fwnode)
> +			fw_devlink_purge_absent_suppliers(fwnode);
> +
>  	/* DT uses "reg" to specify port number. */
>  	port_prop = dev->of_node ? "reg" : "port-number";
>  	device_for_each_child_node(dev, fwnode) {
> -- 
> 2.39.0.314.g84b9a713c41-goog

-- 
heikki