linux-kernel - Re: [PATCH RFC 2/2] phy: phy-can-transceiver: Add support for setting mux

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Date:   Fri, 12 Nov 2021 09:40:27 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Aswath Govindraju <a-govindraju@...com>
Cc:     Vignesh Raghavendra <vigneshr@...com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Nishanth Menon <nm@...com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Vinod Koul <vkoul@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, linux-can@...r.kernel.org,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Peter Rosin <peda@...ntia.se>
Subject: Re: [PATCH RFC 2/2] phy: phy-can-transceiver: Add support for
 setting mux

On 11.11.2021 22:13:12, Aswath Govindraju wrote:
> On some boards, for routing CAN signals from controller to transceiver,
> muxes might need to be set. Therefore, add support for setting the mux by
> reading the mux-controls property from the device tree node.
> 
> Signed-off-by: Aswath Govindraju <a-govindraju@...com>
> ---
>  drivers/phy/phy-can-transceiver.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/phy/phy-can-transceiver.c b/drivers/phy/phy-can-transceiver.c
> index 6f3fe37dee0e..3d8da5226e27 100644
> --- a/drivers/phy/phy-can-transceiver.c
> +++ b/drivers/phy/phy-can-transceiver.c
> @@ -10,6 +10,7 @@
>  #include<linux/module.h>
>  #include<linux/gpio.h>
>  #include<linux/gpio/consumer.h>
> +#include <linux/mux/consumer.h>
>  
>  struct can_transceiver_data {
>  	u32 flags;
> @@ -21,13 +22,22 @@ struct can_transceiver_phy {
>  	struct phy *generic_phy;
>  	struct gpio_desc *standby_gpio;
>  	struct gpio_desc *enable_gpio;
> +	struct mux_control *mux_ctrl;
>  };
>  
>  /* Power on function */
>  static int can_transceiver_phy_power_on(struct phy *phy)
>  {
> +	int ret;
>  	struct can_transceiver_phy *can_transceiver_phy = phy_get_drvdata(phy);
>  
> +	if (can_transceiver_phy->mux_ctrl) {
> +		ret = mux_control_select(can_transceiver_phy->mux_ctrl, 1);

Hard coding the "1" looks wrong here. I have seen some boards where you
can select between a CAN-2.0 and a single wire CAN transceiver with a
mux. So I think we cannot hard code the "1" here.

> +		if (ret) {
> +			dev_err(&phy->dev, "Failed to select CAN mux: %d\n", ret);
> +			return ret;
> +		}
> +	}
>  	if (can_transceiver_phy->standby_gpio)
>  		gpiod_set_value_cansleep(can_transceiver_phy->standby_gpio, 0);
>  	if (can_transceiver_phy->enable_gpio)
> @@ -45,6 +55,8 @@ static int can_transceiver_phy_power_off(struct phy *phy)
>  		gpiod_set_value_cansleep(can_transceiver_phy->standby_gpio, 1);
>  	if (can_transceiver_phy->enable_gpio)
>  		gpiod_set_value_cansleep(can_transceiver_phy->enable_gpio, 0);
> +	if (can_transceiver_phy->mux_ctrl)
> +		mux_control_deselect(can_transceiver_phy->mux_ctrl);
>  
>  	return 0;
>  }
> @@ -95,6 +107,15 @@ 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;
>  
> +	if (of_property_read_bool(dev->of_node, "mux-controls")) {

Is this the proper way of doing this? Looks like we need a
devm_mux_control_get_optional(), which doesn't return a -ENODEV if the
device doesn't exist.

Cc'ed Peter Rosin.

> +		struct mux_control *control;
> +
> +		control = devm_mux_control_get(dev, NULL);
> +		if (IS_ERR(control))
> +			return PTR_ERR(control);

What about making use of dev_err_probe()?

> +		can_transceiver_phy->mux_ctrl = control;
> +	}
> +
>  	phy = devm_phy_create(dev, dev->of_node,
>  			      &can_transceiver_phy_ops);
>  	if (IS_ERR(phy)) {
> -- 
> 2.17.1
> 
>

Regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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