RE: [PATCH v2] can: rcar_canfd: Add Renesas R-Car CAN FD driver

Ramesh Shanmugasundaram
2016-03-07T08:02:10Z

Hi Oliver,

Thanks for the review comments.

> On 03/03/2016 04:38 PM, Ramesh Shanmugasundaram wrote:
>
> > Changes since v1:
> > * Removed testmodes & debugfs code (suggested by Oliver H)
> > * Fixed tx path race issue by introducing lock (suggested by Marc K)
> > * Removed __maybe_unused attribute of rcar_canfd_of_table
> >
>
>
> > obj-$(CONFIG_CAN_M_CAN) += m_can/
> > obj-$(CONFIG_CAN_RCAR) += rcar_can.o
> > +obj-$(CONFIG_CANFD_RCAR) += rcar_canfd.o
>
> Just for the sake of an ordered directory structure:
>
> Would it make sense to create a rcar directory where rcar_can.c and
> rcar_canfd.c are placed?
>
Yes. I'll place them in rcar dir.

> Additionally (besides of one accident with the obsolete PCH_CAN) all CAN
> drivers start with CONFIG_CAN_...
>
> Following that scheme the config option should be named
>
> CONFIG_CAN_RCAR_CANFD
>
> as we had in CONFIG_CAN_IFI_CANFD.

Agreed.

>
> > obj-$(CONFIG_CAN_SJA1000) += sja1000/
> > obj-$(CONFIG_CAN_SUN4I) += sun4i_can.o
> > obj-$(CONFIG_CAN_TI_HECC) += ti_hecc.o
> > diff --git a/drivers/net/can/rcar_canfd.c
> > b/drivers/net/can/rcar_canfd.c
>
> (..)
>
> > +/* Channel priv data */
> > +struct rcar_canfd_channel {
> > + struct can_priv can; /* Must be the first member */
> > + struct net_device *ndev;
> > + struct rcar_canfd_global *gpriv; /* Controller reference */
> > + void __iomem *base; /* Register base address */
> > +#ifdef CONFIG_DEBUG_FS
> > + struct dentry *dev_root;
> > +#endif /* CONFIG_DEBUG_FS */
>
> Some missed stuff from debugfs removal?

:-(. Sorry. Will clean up.

>
> > + struct napi_struct napi;
> > + u8 tx_len[RCANFD_FIFO_DEPTH]; /* For net stats */
> > + u32 tx_head; /* Incremented on xmit */
> > + u32 tx_tail; /* Incremented on xmit done */
> > + u32 channel; /* Channel number */
> > + spinlock_t tx_lock; /* To protect tx path */
> > +};
>
> (..)
>
> > +static int rcar_canfd_start(struct net_device *ndev) {
> > + struct rcar_canfd_channel *priv = netdev_priv(ndev);
> > + int err = -EOPNOTSUPP;
> > + u32 sts, ch = priv->channel;
> > + u32 ridx = ch + RCANFD_RFFIFO_IDX;
> > +
> > + /* Ensure channel starts in FD mode */
> > + if (!(priv->can.ctrlmode & CAN_CTRLMODE_FD)) {
> > + netdev_err(ndev, "enable can fd mode for channel %d\n", ch);
> > + goto fail_mode;
> > + }
>
> What's the reason behind this check?
>
> A CAN FD capable CAN controller can be either configured to run as CAN 2.0
> (Classic CAN) or as CAN FD controller.
>
> So why are to throwing an error here and produce an initialization
> failure?

When this controller is configured in FD mode and used only with CAN 2.0 nodes, it still expects a DTSEG (data bitrate) configuration same as NTSEG (nominal bitrate). This check, specifically in ndo_open, ensures both are configured and will work fine with CAN 2.0 nodes (e.g.)

"ip link set can0 up type can bitrate 1000000 dbitrate 1000000 fd on"

If I don't have this check, a configuration like this

"ip link set can0 up type can bitrate 1000000"

will bring up the controller without DTSEG configured.

Thanks,
Ramesh