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

[Michael Walle]

Am 2020-06-30 18:15, schrieb Oliver Hartkopp:
> On 30.06.20 07:53, Michael Walle wrote:
> > [+ 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>
> > > > ---
> > > > Âdrivers/net/can/flexcan.c | 19 ++++++++++++++++---
> > > > Â1 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 @@
> > > > Â#define FLEXCAN_CTRL2_MRPÂÂÂÂÂÂÂ BIT(18)
> > > > Â#define FLEXCAN_CTRL2_RRSÂÂÂÂÂÂÂ BIT(17)
> > > > Â#define FLEXCAN_CTRL2_EACENÂÂÂÂÂÂÂ BIT(16)
> > > > +#define FLEXCAN_CTRL2_ISOCANFDENÂÂÂ BIT(12)
> > > >
> > > > Â/* FLEXCAN memory error control register (MECR) bits */
> > > > Â#define FLEXCAN_MECR_ECRWRDISÂÂÂÂÂÂÂ BIT(31)
> > > > @@ -1344,14 +1345,25 @@ static int flexcan_chip_start(struct 
> > > > net_device
> > > > *dev)
> > > > ÂÂÂÂ else
> > > > ÂÂÂÂÂÂÂÂ reg_mcr |= FLEXCAN_MCR_SRX_DIS;
> > > >
> > > > -ÂÂÂ /* MCR - CAN-FD */
> > > > -ÂÂÂ if (priv->can.ctrlmode & CAN_CTRLMODE_FD)
> > > > +ÂÂÂ /* MCR, CTRL2
> > > > +ÂÂÂÂ *
> > > > +ÂÂÂÂ * CAN-FD mode
> > > > +ÂÂÂÂ * ISO CAN-FD mode
> > > > +ÂÂÂÂ */
> > > > +ÂÂÂ reg_ctrl2 = priv->read(&regs->ctrl2);
> > > > +ÂÂÂ if (priv->can.ctrlmode & CAN_CTRLMODE_FD) {
> > > > ÂÂÂÂÂÂÂÂ reg_mcr |= FLEXCAN_MCR_FDEN;
> > > > -ÂÂÂ else
> > > > +ÂÂÂÂÂÂÂ reg_ctrl2 |= FLEXCAN_CTRL2_ISOCANFDEN;
> > > > +ÂÂÂ } else {
> > > > ÂÂÂÂÂÂÂÂ reg_mcr &= ~FLEXCAN_MCR_FDEN;
> > > > +ÂÂÂ }
> > > > +
> > > > +ÂÂÂ if (priv->can.ctrlmode & CAN_CTRLMODE_FD_NON_ISO)
> > > > +ÂÂÂÂÂÂÂ reg_ctrl2 &= ~FLEXCAN_CTRL2_ISOCANFDEN;

[1]

> > [..]
> > > 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 \
> > > ÂÂ 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:
> >  Â /* do not check for static fd-non-iso if 'fd' is disabled */
> >  Â if (!(maskedflags & CAN_CTRLMODE_FD))
> >  ÂÂÂÂÂÂÂÂÂ 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?
>
> CAN_CTRLMODE_FD_NON_ISO is only relevant when CAN_CTRLMODE_FD is set.
>
> So in the example from above
>
> ip link set can0 up type can bitrate 1000000 dbitrate 5000000 
> fd-non-iso on
>
> either the setting of 'dbitrate 5000000' and 'fd-non-iso on' is 
> pointless.
>
> When switching to FD-mode with 'fd on' the FD relevant settings need
> to be applied.
>
> FD ISO is the default.
>
> Did this help or did I get anything wrong?

Thanks for the explanation. Yes this helped a great deal and this
patch should be correct; it sets ISO mode if CAN_CTRLMODE_FD is set
and masks it again if CAN_CTRLMODE_FD_NON_ISO is set. See [1].

-michael