Re: [PATCH] usb: typec: mux: avoid duplicated mux switches

[Sebastian Reichel]

Hi,

On Sat, Aug 22, 2026 at 09:24:58AM +0200, Marek Vasut wrote:
> Some devices use combo PHYs (i.e. USB3 + DisplayPort), which also
> handle the lane muxing. These PHYs are referenced twice from
> the USB-C connector (USB super-speed lines and SBU/AUX lines)
> resulting in the mux being configured twice. Avoid this by
> dropping duplicates.
> 
> This is a re-application of b145c3f29d62 ("usb: typec: mux: avoid
> duplicated mux switches"), with fix derived from usb: typec: mux:
> Fix typec_switch_match() .
> 
> Fixes: f576c75f95a5 ("Revert "usb: typec: mux: avoid duplicated mux switches"")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
> Co-developed-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
> Signed-off-by: Marek Vasut <marex@xxxxxxxxxxxx>
> ---
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> Cc: Jens Glathe <jens.glathe@xxxxxxxxxxxxxxxxxxxxxx>
> Cc: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
> Cc: kernel@xxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-usb@xxxxxxxxxxxxxxx
> ---
> - Extensive test by Jens https://lore.kernel.org/all/8bdf6062-8ec2-4c30-8463-0368d3a0f1ce@xxxxxxxxxxxxxxxxxxxxxx/

Thanks for the fixed version. It looks mostly good to me, but it
should also take the other fix into account and initialize
mux_devs to {} in fwnode_typec_mux_get():

https://lore.kernel.org/linux-usb/20260804083434.20885-1-i@xxxxx/

Greetings,

-- Sebastian

> ---
>  drivers/usb/typec/mux.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/mux.c b/drivers/usb/typec/mux.c
> index 2bc7e8edb3cbd..afa6fc1813978 100644
> --- a/drivers/usb/typec/mux.c
> +++ b/drivers/usb/typec/mux.c
> @@ -277,7 +277,9 @@ static int mux_fwnode_match(struct device *dev, const void *fwnode)
>  static void *typec_mux_match(const struct fwnode_handle *fwnode,
>  			     const char *id, void *data)
>  {
> +	struct typec_mux_dev **mux_devs = data;
>  	struct device *dev;
> +	int i;
>  
>  	/*
>  	 * Device graph (OF graph) does not give any means to identify the
> @@ -292,8 +294,18 @@ static void *typec_mux_match(const struct fwnode_handle *fwnode,
>  
>  	dev = class_find_device(&typec_mux_class, NULL, fwnode,
>  				mux_fwnode_match);
> +	if (!dev)
> +		return ERR_PTR(-EPROBE_DEFER);
>  
> -	return dev ? to_typec_mux_dev(dev) : ERR_PTR(-EPROBE_DEFER);
> +	/* Skip duplicates */
> +	for (i = 0; i < TYPEC_MUX_MAX_DEVS; i++)
> +		if (to_typec_mux_dev(dev) == mux_devs[i]) {
> +			put_device(dev);
> +			return NULL;
> +		}
> +
> +
> +	return to_typec_mux_dev(dev);
>  }
>  
>  /**
> @@ -318,7 +330,8 @@ struct typec_mux *fwnode_typec_mux_get(struct fwnode_handle *fwnode)
>  		return ERR_PTR(-ENOMEM);
>  
>  	count = fwnode_connection_find_matches(fwnode, "mode-switch",
> -					       NULL, typec_mux_match,
> +					       (void **)mux_devs,
> +					       typec_mux_match,
>  					       (void **)mux_devs,
>  					       ARRAY_SIZE(mux_devs));
>  	if (count <= 0) {
> -- 
> 2.53.0
>

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