linux-kernel - Re: [PATCH v2] phy: can-transceiver: Re-instate "mux-states" property presence check

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Message-ID: <7805e0db-7c17-438d-9985-f4feec644da6@wanadoo.fr>
Date: Fri, 21 Mar 2025 13:18:18 +0900
From: Vincent Mailhol <mailhol.vincent@...adoo.fr>
To: Geert Uytterhoeven <geert+renesas@...der.be>,
 Rob Herring <robh@...nel.org>
Cc: linux-can@...r.kernel.org, linux-phy@...ts.infradead.org,
 linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
 Marc Kleine-Budde <mkl@...gutronix.de>, Vinod Koul <vkoul@...nel.org>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Peter Rosin <peda@...ntia.se>,
 Aswath Govindraju <a-govindraju@...com>,
 Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v2] phy: can-transceiver: Re-instate "mux-states" property
 presence check

On 21/03/2025 at 00:15, Geert Uytterhoeven wrote:
> On the Renesas Gray Hawk Single development board:
> 
>     can-transceiver-phy can-phy0: /can-phy0: failed to get mux-state (0)
> 
> "mux-states" is an optional property for CAN transceivers.  However,
> mux_get() always prints an error message in case of an error, including
> when the property is not present, confusing the user.
> 
> Fix this by re-instating the property presence check (this time using
> the proper API) in a wrapper around devm_mux_state_get().  When the
> multiplexer subsystem gains support for optional muxes, the wrapper can
> just be removed.
> 
> In addition, propagate all real errors upstream, instead of ignoring
> them.

I would like to hear Rob's opinion on this. In d02dfd4ceb2e9f34 Rob
purposely changed the function to ignore errors other than EPROBE_DEFER.

Right now, I do not see a reason not to propagate the other errors, so
I am in favor of this roll back. But maybe we are missing something?

Otherwise, the patch looks good to me. Nice improvement over the v1. I
will wait for Rob's comment to give my review tag.

> Fixes: d02dfd4ceb2e9f34 ("phy: can-transceiver: Drop unnecessary "mux-states" property presence check")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> Alternatively, the multiplexer subsystem needs to gain support for
> getting an optional mux...
> 
> v2:
>   - Add and use devm_mux_state_get_optional(),
>   - No given tags added, as the new solution is different.
> ---
>  drivers/phy/phy-can-transceiver.c | 22 +++++++++++++++-------
>  1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/phy/phy-can-transceiver.c b/drivers/phy/phy-can-transceiver.c
> index 2bec70615449f94d..f59caff4b3d4c267 100644
> --- a/drivers/phy/phy-can-transceiver.c
> +++ b/drivers/phy/phy-can-transceiver.c
> @@ -93,6 +93,16 @@ static const struct of_device_id can_transceiver_phy_ids[] = {
>  };
>  MODULE_DEVICE_TABLE(of, can_transceiver_phy_ids);
>  
> +/* Temporary wrapper until the multiplexer subsystem supports optional muxes */
> +static inline struct mux_state *
> +devm_mux_state_get_optional(struct device *dev, const char *mux_name)
> +{
> +	if (!of_property_present(dev->of_node, "mux-states"))
> +		return NULL;
> +
> +	return devm_mux_state_get(dev, mux_name);
> +}
> +
>  static int can_transceiver_phy_probe(struct platform_device *pdev)
>  {
>  	struct phy_provider *phy_provider;
> @@ -114,13 +124,11 @@ static int can_transceiver_phy_probe(struct platform_device *pdev)
>  	match = of_match_node(can_transceiver_phy_ids, pdev->dev.of_node);
>  	drvdata = match->data;
>  
> -	mux_state = devm_mux_state_get(dev, NULL);
> -	if (IS_ERR(mux_state)) {
> -		if (PTR_ERR(mux_state) == -EPROBE_DEFER)> -			return PTR_ERR(mux_state);
> -	} else {
> -		can_transceiver_phy->mux_state = mux_state;
> -	}
> +	mux_state = devm_mux_state_get_optional(dev, NULL);
> +	if (IS_ERR(mux_state))
> +		return PTR_ERR(mux_state);
> +
> +	can_transceiver_phy->mux_state = mux_state;
>  
>  	phy = devm_phy_create(dev, dev->of_node,
>  			      &can_transceiver_phy_ops);

Yours sincerely,
Vincent Mailhol