linux-kernel - Re: [patch 01/12] can: c_can: Wait for CONTROL

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Message-ID: <53288C47.5090308@pengutronix.de>
Date:	Tue, 18 Mar 2014 19:11:19 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>
CC:	Wolfgang Grandegger <wg@...ndegger.com>,
	Markus Pargmann <mpa@...gutronix.de>,
	Benedikt Spranger <b.spranger@...utronix.de>,
	linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [patch 01/12] can: c_can: Wait for CONTROL_INIT to be cleared

On 03/18/2014 06:19 PM, Thomas Gleixner wrote:
> According to the documentation the CPU must wait for CONTROL_INIT to
> be cleared before writing to the baudrate registers.

Thanks for the catch.

> Signed-off-by: Benedikt Spranger <b.spranger@...utronix.de>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>
> ---
>  drivers/net/can/c_can/c_can.c |   26 +++++++++++++++++++++++---
>  1 file changed, 23 insertions(+), 3 deletions(-)
> 
> Index: linux/drivers/net/can/c_can/c_can.c
> ===================================================================
> --- linux.orig/drivers/net/can/c_can/c_can.c
> +++ linux/drivers/net/can/c_can/c_can.c
> @@ -566,6 +566,21 @@ static netdev_tx_t c_can_start_xmit(stru
>  	return NETDEV_TX_OK;
>  }
>  
> +static int c_can_wait_for_ctrl_init(struct net_device *dev,
> +				    struct c_can_priv *priv, u32 init)
> +{
> +	int retry = 0;
> +
> +	while (init != (priv->read_reg(priv, C_CAN_CTRL_REG) & CONTROL_INIT)) {
> +		udelay(10);
> +		if (retry++ > 1000) {
> +			netdev_err(dev, "CCTRL: set CONTROL_INIT failed\n");
> +			return -EIO;
> +		}
> +	}
> +	return 0;
> +}
> +
>  static int c_can_set_bittiming(struct net_device *dev)
>  {
>  	unsigned int reg_btr, reg_brpe, ctrl_save;
> @@ -573,6 +588,7 @@ static int c_can_set_bittiming(struct ne
>  	u32 ten_bit_brp;
>  	struct c_can_priv *priv = netdev_priv(dev);
>  	const struct can_bittiming *bt = &priv->can.bittiming;
> +	int res;
>  
>  	/* c_can provides a 6-bit brp and 4-bit brpe fields */
>  	ten_bit_brp = bt->brp - 1;
> @@ -590,13 +606,17 @@ static int c_can_set_bittiming(struct ne
>  		"setting BTR=%04x BRPE=%04x\n", reg_btr, reg_brpe);
>  
>  	ctrl_save = priv->read_reg(priv, C_CAN_CTRL_REG);
> -	priv->write_reg(priv, C_CAN_CTRL_REG,
> -			ctrl_save | CONTROL_CCE | CONTROL_INIT);
> +	ctrl_save &= ~CONTROL_INIT;
> +	priv->write_reg(priv, C_CAN_CTRL_REG, CONTROL_CCE | CONTROL_INIT);
> +	res = c_can_wait_for_ctrl_init(dev, priv, CONTROL_INIT);
> +	if (res)
> +		return res;
> +
>  	priv->write_reg(priv, C_CAN_BTR_REG, reg_btr);
>  	priv->write_reg(priv, C_CAN_BRPEXT_REG, reg_brpe);
>  	priv->write_reg(priv, C_CAN_CTRL_REG, ctrl_save);
>  
> -	return 0;
> +	return c_can_wait_for_ctrl_init(dev, priv, 0);

I'll post a patch that adds return value checking of all direct and
indirect users of c_can_set_bittiming().

>  }
>  
>  /*

Thanks,
Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
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