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

Marc Kleine-Budde
2016-03-07T08:08:21Z

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On 03/07/2016 09:02 AM, Ramesh Shanmugasundaram wrote:
> 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.

That should bring up the controller in CAN 2.0 mode.

Marc

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