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

[Michael Walle]

[+ Oliver]

Hi Joakim,

Am 2020-06-30 04:42, schrieb Joakim Zhang:
> > -----Original Message-----
> > From: Michael Walle <michael@xxxxxxxx>
> > Sent: 2020å6æ30æ 2:18
> > To: linux-can@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx
> > Cc: Wolfgang Grandegger <wg@xxxxxxxxxxxxxx>; Marc Kleine-Budde
> > <mkl@xxxxxxxxxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>; Jakub
> > Kicinski <kuba@xxxxxxxxxx>; Joakim Zhang <qiangqing.zhang@xxxxxxx>;
> > dl-linux-imx <linux-imx@xxxxxxx>; Michael Walle <michael@xxxxxxxx>
> > 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@xxxxxxxx>
> > ---
> >  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