netdev - Re: [PATCH v5 6/8] net: can: c_can: Disable pins when CAN interface is down

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Message-ID: <5464D661.7080505@pengutronix.de>
Date:	Thu, 13 Nov 2014 17:03:45 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Roger Quadros <rogerq@...com>, wg@...ndegger.com
CC:	wsa@...-dreams.de, tony@...mide.com, tglx@...utronix.de,
	mugunthanvnm@...com, george.cherian@...com, balbi@...com,
	nsekhar@...com, nm@...com, sergei.shtylyov@...entembedded.com,
	linux-omap@...r.kernel.org, linux-can@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH v5 6/8] net: can: c_can: Disable pins when CAN interface
 is down

On 11/13/2014 04:23 PM, Roger Quadros wrote:
> DRA7 CAN IP suffers from a problem which causes it to be prevented
> from fully turning OFF (i.e. stuck in transition) if the module was
> disabled while there was traffic on the CAN_RX line.
> 
> To work around this issue we select the SLEEP pin state by default
> on probe and use the DEFAULT pin state on CAN up and back to the
> SLEEP pin state on CAN down.
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  drivers/net/can/c_can/c_can.c | 37 +++++++++++++++++++++++++++++++++++++
>  drivers/net/can/c_can/c_can.h |  1 +
>  2 files changed, 38 insertions(+)
> 
> diff --git a/drivers/net/can/c_can/c_can.c b/drivers/net/can/c_can/c_can.c
> index 8e78bb4..c80cb3d 100644
> --- a/drivers/net/can/c_can/c_can.c
> +++ b/drivers/net/can/c_can/c_can.c
> @@ -35,6 +35,7 @@
>  #include <linux/list.h>
>  #include <linux/io.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/pinctrl/consumer.h>
>  
>  #include <linux/can.h>
>  #include <linux/can/dev.h>
> @@ -587,6 +588,21 @@ static int c_can_chip_config(struct net_device *dev)
>  	return c_can_set_bittiming(dev);
>  }
>  
> +/*
> + * Selects the pinctrl state specified in the name.
> + */
> +static void c_can_pinctrl_select_state(struct c_can_priv *priv,
> +				      const char *name)
> +{
> +	if (!IS_ERR(priv->pinctrl)) {
> +		struct pinctrl_state *s;
> +
> +		s = pinctrl_lookup_state(priv->pinctrl, name);
> +		if (!IS_ERR(s))
> +			pinctrl_select_state(priv->pinctrl, s);
> +	}
> +}
> +
>  static int c_can_start(struct net_device *dev)
>  {
>  	struct c_can_priv *priv = netdev_priv(dev);
> @@ -603,6 +619,8 @@ static int c_can_start(struct net_device *dev)
>  
>  	priv->can.state = CAN_STATE_ERROR_ACTIVE;
>  
> +	/* activate pins */
> +	c_can_pinctrl_select_state(priv, PINCTRL_STATE_DEFAULT);
>  	return 0;
>  }
>  
> @@ -611,6 +629,9 @@ static void c_can_stop(struct net_device *dev)
>  	struct c_can_priv *priv = netdev_priv(dev);
>  
>  	c_can_irq_control(priv, false);
> +
> +	/* deactivate pins */
> +	c_can_pinctrl_select_state(priv, PINCTRL_STATE_SLEEP);
>  	priv->can.state = CAN_STATE_STOPPED;
>  }
>  
> @@ -1244,6 +1265,22 @@ int register_c_can_dev(struct net_device *dev)
>  	struct c_can_priv *priv = netdev_priv(dev);
>  	int err;
>  
> +	priv->pinctrl = devm_pinctrl_get(dev->dev.parent);

What's dev->dev.parent?
Ah, this is set by SET_NETDEV_DEV(dev, &pdev->dev); Good work!

I thought we had to set priv->pinctrl in the platform.c.

> +	if (!IS_ERR(priv->pinctrl)) {
> +		struct pinctrl_state *s;
> +
> +		/* Deactivate pins to prevent DRA7 DCAN IP from being
> +		 * stuck in transition when module is disabled.
> +		 * Pins are activated in c_can_start() and deactivated
> +		 * in c_can_stop()
> +		 */
> +		s = pinctrl_lookup_state(priv->pinctrl, PINCTRL_STATE_SLEEP);
> +		if (!IS_ERR(s))
> +			pinctrl_select_state(priv->pinctrl, s);
> +	} else {
> +		netdev_dbg(dev, "failed to get pinctrl\n");
> +	}
> +
The above can be replace by this?

	c_can_pinctrl_select_state(priv, PINCTRL_STATE_SLEEP)

Then we don't have the worrying looking error message if there isn't any
pinctrl, e.g. for the PCI driver with pinctrl enabled in the Kernel.

I just stumbled over pinctrl_pm_select_sleep_state(), is it possible to
integrate this into runtime pm?

http://lxr.free-electrons.com/source/drivers/pinctrl/core.c#L1282

>  	c_can_pm_runtime_enable(priv);
>  
>  	dev->flags |= IFF_ECHO;	/* we support local echo */
> diff --git a/drivers/net/can/c_can/c_can.h b/drivers/net/can/c_can/c_can.h
> index c6715ca..3cedf48 100644
> --- a/drivers/net/can/c_can/c_can.h
> +++ b/drivers/net/can/c_can/c_can.h
> @@ -210,6 +210,7 @@ struct c_can_priv {
>  	u32 comm_rcv_high;
>  	u32 rxmasked;
>  	u32 dlc[C_CAN_MSG_OBJ_TX_NUM];
> +	struct pinctrl *pinctrl;
>  };
>  
>  struct net_device *alloc_c_can_dev(void);
> 

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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