netdev - Re: [PATCH] flexcan: disable bus error interrupts for the i.MX28

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Date:	Sun, 7 Oct 2012 11:09:00 +0800
From:	Shawn Guo <shawn.guo@...aro.org>
To:	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>,
	Linux-CAN <linux-can@...r.kernel.org>,
	Hui Wang <jason77.wang@...il.com>,
	Dong Aisheng <b29396@...escale.com>
Subject: Re: [PATCH] flexcan: disable bus error interrupts for the i.MX28

On Fri, Sep 28, 2012 at 03:17:15PM +0200, Wolfgang Grandegger wrote:
> Due to a bug in most Flexcan cores, the bus error interrupt needs
> to be enabled. Otherwise we don't get any error warning or passive
> interrupts. This is _not_ necessay for the i.MX28 and this patch
> disables bus error interrupts if "berr-reporting" is not requested.
> This avoids bus error flooding, which might harm, especially on
> low-end systems.
> 
> To handle such quirks of the Flexcan cores, a hardware feature flag
> has been introduced, also replacing the "hw_ver" variable. So far
> nobody could tell what Flexcan core version is available on what
> Freescale SOC, apart from the i.MX6Q and P1010, and which bugs or
> features are present on the various "hw_rev".
> 
> CC: Hui Wang <jason77.wang@...il.com>
> CC: Shawn Guo <shawn.guo@...aro.org>
> Signed-off-by: Wolfgang Grandegger <wg@...ndegger.com>
> ---
> 
> Concerning the bug, I know that the i.MX35 does have it. Maybe other
> Flexcan cores than on the i.MX28 does *not* have it either. If you
> have a chance, please check on the P1010, i.MX6Q, i.MX51, i.MX53,
> etc.

>From what I can tell, i.MX35, i.MX51 and i.MX53 use the same version,
so they should all have the bug.  And for i.MX6Q, since it uses a newer
version even than i.MX28, I would believe it's affected by the bug.
But I'm copying Dong who should have better knowledge about this to
confirm. 

Shawn

> 
> Wolfgang.
> 
> 
>  drivers/net/can/flexcan.c |   29 +++++++++++++++++++----------
>  1 files changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> index c5f1431..c78ecfc 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -144,6 +144,10 @@
>  
>  #define FLEXCAN_MB_CODE_MASK		(0xf0ffffff)
>  
> +/* FLEXCAN hardware feature flags */
> +#define FLEXCAN_HAS_V10_FEATURES	BIT(1) /* For core version >= 10 */
> +#define FLEXCAN_HAS_BROKEN_ERR_STATE	BIT(2) /* Broken error state handling */
> +
>  /* Structure of the message buffer */
>  struct flexcan_mb {
>  	u32 can_ctrl;
> @@ -178,7 +182,7 @@ struct flexcan_regs {
>  };
>  
>  struct flexcan_devtype_data {
> -	u32 hw_ver;	/* hardware controller version */
> +	u32 features;	/* hardware controller features */
>  };
>  
>  struct flexcan_priv {
> @@ -197,11 +201,11 @@ struct flexcan_priv {
>  };
>  
>  static struct flexcan_devtype_data fsl_p1010_devtype_data = {
> -	.hw_ver = 3,
> +	.features = FLEXCAN_HAS_BROKEN_ERR_STATE,
>  };
> -
> +static struct flexcan_devtype_data fsl_imx28_devtype_data;
>  static struct flexcan_devtype_data fsl_imx6q_devtype_data = {
> -	.hw_ver = 10,
> +	.features = FLEXCAN_HAS_V10_FEATURES | FLEXCAN_HAS_BROKEN_ERR_STATE,
>  };
>  
>  static const struct can_bittiming_const flexcan_bittiming_const = {
> @@ -741,15 +745,19 @@ static int flexcan_chip_start(struct net_device *dev)
>  	 * enable tx and rx warning interrupt
>  	 * enable bus off interrupt
>  	 * (== FLEXCAN_CTRL_ERR_STATE)
> -	 *
> -	 * _note_: we enable the "error interrupt"
> -	 * (FLEXCAN_CTRL_ERR_MSK), too. Otherwise we don't get any
> -	 * warning or bus passive interrupts.
>  	 */
>  	reg_ctrl = flexcan_read(&regs->ctrl);
>  	reg_ctrl &= ~FLEXCAN_CTRL_TSYN;
>  	reg_ctrl |= FLEXCAN_CTRL_BOFF_REC | FLEXCAN_CTRL_LBUF |
> -		FLEXCAN_CTRL_ERR_STATE | FLEXCAN_CTRL_ERR_MSK;
> +		FLEXCAN_CTRL_ERR_STATE;
> +	/*
> +	 * enable the "error interrupt" (FLEXCAN_CTRL_ERR_MSK),
> +	 * on most Flexcan cores, too. Otherwise we don't get
> +	 * any error warning or passive interrupts.
> +	 */
> +	if (priv->devtype_data->features & FLEXCAN_HAS_BROKEN_ERR_STATE ||
> +	    priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING)
> +		reg_ctrl |= FLEXCAN_CTRL_ERR_MSK;
>  
>  	/* save for later use */
>  	priv->reg_ctrl_default = reg_ctrl;
> @@ -772,7 +780,7 @@ static int flexcan_chip_start(struct net_device *dev)
>  	flexcan_write(0x0, &regs->rx14mask);
>  	flexcan_write(0x0, &regs->rx15mask);
>  
> -	if (priv->devtype_data->hw_ver >= 10)
> +	if (priv->devtype_data->features & FLEXCAN_HAS_V10_FEATURES)
>  		flexcan_write(0x0, &regs->rxfgmask);
>  
>  	flexcan_transceiver_switch(priv, 1);
> @@ -954,6 +962,7 @@ static void __devexit unregister_flexcandev(struct net_device *dev)
>  
>  static const struct of_device_id flexcan_of_match[] = {
>  	{ .compatible = "fsl,p1010-flexcan", .data = &fsl_p1010_devtype_data, },
> +	{ .compatible = "fsl,imx28-flexcan", .data = &fsl_imx28_devtype_data, },
>  	{ .compatible = "fsl,imx6q-flexcan", .data = &fsl_imx6q_devtype_data, },
>  	{ /* sentinel */ },
>  };
> -- 
> 1.7.7.6
> 
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