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Date:	Sun, 07 Oct 2012 16:48:39 +0200
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Shawn Guo <shawn.guo@...aro.org>
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 10/07/2012 05:09 AM, Shawn Guo wrote:
> 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. 

Thank for clarification. I have a i.MX6Q board but without CAN adapter
:(, unfortunately. Otherwise I would try it out myself.

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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