netdev - Re: [PATCH 2/2] can: flexcan: add support for ISO CAN-FD

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Date:   Tue, 30 Jun 2020 07:53:17 +0200
From:   Michael Walle <michael@...le.cc>
To:     Joakim Zhang <qiangqing.zhang@....com>
Cc:     linux-can@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        Oliver Hartkopp <socketcan@...tkopp.net>
Subject: Re: [PATCH 2/2] can: flexcan: add support for ISO CAN-FD

[+ Oliver]

Hi Joakim,

Am 2020-06-30 04:42, schrieb Joakim Zhang:
>> -----Original Message-----
>> From: Michael Walle <michael@...le.cc>
>> Sent: 2020年6月30日 2:18
>> To: linux-can@...r.kernel.org; netdev@...r.kernel.org;
>> linux-kernel@...r.kernel.org
>> Cc: Wolfgang Grandegger <wg@...ndegger.com>; Marc Kleine-Budde
>> <mkl@...gutronix.de>; David S . Miller <davem@...emloft.net>; Jakub
>> Kicinski <kuba@...nel.org>; Joakim Zhang <qiangqing.zhang@....com>;
>> dl-linux-imx <linux-imx@....com>; Michael Walle <michael@...le.cc>
>> Subject: [PATCH 2/2] can: flexcan: add support for ISO CAN-FD
>> 
>> Up until now, the controller used non-ISO CAN-FD mode, although it 
>> supports it.
>> Add support for ISO mode, too. By default the hardware is in non-ISO 
>> mode and
>> an enable bit has to be explicitly set.
>> 
>> Signed-off-by: Michael Walle <michael@...le.cc>
>> ---
>>  drivers/net/can/flexcan.c | 19 ++++++++++++++++---
>>  1 file changed, 16 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c 
>> index
>> 183e094f8d66..a92d3cdf4195 100644
>> --- a/drivers/net/can/flexcan.c
>> +++ b/drivers/net/can/flexcan.c
>> @@ -94,6 +94,7 @@
>>  #define FLEXCAN_CTRL2_MRP		BIT(18)
>>  #define FLEXCAN_CTRL2_RRS		BIT(17)
>>  #define FLEXCAN_CTRL2_EACEN		BIT(16)
>> +#define FLEXCAN_CTRL2_ISOCANFDEN	BIT(12)
>> 
>>  /* FLEXCAN memory error control register (MECR) bits */
>>  #define FLEXCAN_MECR_ECRWRDIS		BIT(31)
>> @@ -1344,14 +1345,25 @@ static int flexcan_chip_start(struct 
>> net_device
>> *dev)
>>  	else
>>  		reg_mcr |= FLEXCAN_MCR_SRX_DIS;
>> 
>> -	/* MCR - CAN-FD */
>> -	if (priv->can.ctrlmode & CAN_CTRLMODE_FD)
>> +	/* MCR, CTRL2
>> +	 *
>> +	 * CAN-FD mode
>> +	 * ISO CAN-FD mode
>> +	 */
>> +	reg_ctrl2 = priv->read(&regs->ctrl2);
>> +	if (priv->can.ctrlmode & CAN_CTRLMODE_FD) {
>>  		reg_mcr |= FLEXCAN_MCR_FDEN;
>> -	else
>> +		reg_ctrl2 |= FLEXCAN_CTRL2_ISOCANFDEN;
>> +	} else {
>>  		reg_mcr &= ~FLEXCAN_MCR_FDEN;
>> +	}
>> +
>> +	if (priv->can.ctrlmode & CAN_CTRLMODE_FD_NON_ISO)
>> +		reg_ctrl2 &= ~FLEXCAN_CTRL2_ISOCANFDEN;
> 
> 

[..]
> ip link set can0 up type can bitrate 1000000 dbitrate 5000000 fd on
> ip link set can0 up type can bitrate 1000000 dbitrate 5000000 fd on \
>    fd-non-iso on

vs.

> ip link set can0 up type can bitrate 1000000 dbitrate 5000000 
> fd-non-iso on

I haven't found anything if CAN_CTRLMODE_FD_NON_ISO depends on
CAN_CTRLMODE_FD. I.e. wether CAN_CTRLMODE_FD_NON_ISO can only be set if
CAN_CTRLMODE_FD is also set.

Only the following piece of code, which might be a hint that you
have to set CAN_CTRLMODE_FD if you wan't to use CAN_CTRLMODE_FD_NON_ISO:

drivers/net/can/dev.c:
   /* do not check for static fd-non-iso if 'fd' is disabled */
   if (!(maskedflags & CAN_CTRLMODE_FD))
           ctrlstatic &= ~CAN_CTRLMODE_FD_NON_ISO;

If CAN_CTRLMODE_FD_NON_ISO can be set without CAN_CTRLMODE_FD, what
should be the mode if both are set at the same time?

Marc? Oliver?

-michael