Subject: Re: [PATCH 2/4] net: can: ifi: Fix TX DLC configuration

From: Oliver Hartkopp <[email-masked]>
Date: Wed, 2 Mar 2016 07:12:58 +0100

On 03/01/2016 10:27 PM, Marek Vasut wrote:
> On 03/01/2016 07:11 PM, Oliver Hartkopp wrote:
> 
> Hi!
> 
>> On 02/29/2016 08:59 PM, Marek Vasut wrote:
>>> The TX DLC, the transmission length information, was not written
>>> into the transmit configuration register. When using the CAN core
>>> with different CAN controller, the receiving CAN controller will
>>> receive only the ID part of the CAN frame, but no data at all.
>>>
>>> This patch adds the TX DLC into the register to fix this issue.
>>>
>>> Signed-off-by: Marek Vasut <[email-masked]>
>>> Cc: Marc Kleine-Budde <[email-masked]>
>>> Cc: Mark Rutland <[email-masked]>
>>> Cc: Oliver Hartkopp <[email-masked]>
>>> Cc: Wolfgang Grandegger <[email-masked]>
>>> ---
>>>  drivers/net/can/ifi_canfd/ifi_canfd.c | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/drivers/net/can/ifi_canfd/ifi_canfd.c b/drivers/net/can/ifi_canfd/ifi_canfd.c
>>> index 72f5205..82a33bd 100644
>>> --- a/drivers/net/can/ifi_canfd/ifi_canfd.c
>>> +++ b/drivers/net/can/ifi_canfd/ifi_canfd.c
>>> @@ -774,10 +774,15 @@ static netdev_tx_t ifi_canfd_start_xmit(struct sk_buff *skb,
>>>  
>>>  	if (priv->can.ctrlmode & (CAN_CTRLMODE_FD | CAN_CTRLMODE_FD_NON_ISO)) {
>>>  		if (can_is_canfd_skb(skb)) {
>>> +			txdlc |= can_len2dlc(cf->len);
>>>  			txdlc |= IFI_CANFD_TXFIFO_DLC_EDL;
>>>  			if (cf->flags & CANFD_BRS)
>>>  				txdlc |= IFI_CANFD_TXFIFO_DLC_BRS;
>>> +		} else {
>>> +			txdlc |= cf->len;
>>>  		}
>>> +	} else {
>>> +		txdlc |= cf->len;
>>>  	}
>>
>> Please use
>>
>> 	txdlc |= can_len2dlc(cf->len);
>>
>> by default (it works for CAN and CAN FD).
>>
>> So that it looks more like:
>>
>> 	txdlc |= can_len2dlc(cf->len);
> 
> Roger.
> 
>> 	if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) && can_is_canfd_skb(skb)) {
>> 		txdlc |= IFI_CANFD_TXFIFO_DLC_EDL;
>> 		if (cf->flags & CANFD_BRS)
>> 			txdlc |= IFI_CANFD_TXFIFO_DLC_BRS;
>> 	}
>>
>> Testing against CAN_CTRLMODE_FD_NON_ISO is wrong!
>> This configuration bit is just for the protocol on the wire and is no
>> distinction for CAN / CAN FD.
> 
> So CAN_CTRLMODE_FD is always set if the system operates in CAN/FD mode.

Not the 'system' but this specific CAN netdevice.

> And in addition to that, if the system operates in CAN/FD BOSCH mode,
> the CAN_CTRLMODE_FD_NON_ISO is set. Do I understand it correctly ?

Yep! ('the CAN netdev')

Regards,
Oliver