Re: [PATCH v6 4/7] can: Add Nuvoton NCT6694 CANFD support

Vincent Mailhol
2025-01-26T08:56:49Z

Hi Ming,

nct6694_can_handle_state_change() needs some rework. Aside from that a
few comments here and there.

I think that this is getting close to be ready. Hopefully, if everything
get resolved, I will give my approval for this patch on the v7.

On 23/01/2025 at 18:11, Ming Yu wrote:
> This driver supports Socket CANFD functionality for NCT6694 MFD
> device based on USB interface.
>
> Signed-off-by: Ming Yu <a0282524688@gmail.com>
> ---
> MAINTAINERS | 1 +
> drivers/net/can/usb/Kconfig | 11 +
> drivers/net/can/usb/Makefile | 1 +
> drivers/net/can/usb/nct6694_canfd.c | 813 ++++++++++++++++++++++++++++
> 4 files changed, 826 insertions(+)
> create mode 100644 drivers/net/can/usb/nct6694_canfd.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f930252ad132..3196f87c547d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -16808,6 +16808,7 @@ S: Supported
> F: drivers/gpio/gpio-nct6694.c
> F: drivers/i2c/busses/i2c-nct6694.c
> F: drivers/mfd/nct6694.c
> +F: drivers/net/can/usb/nct6694_canfd.c
> F: include/linux/mfd/nct6694.h
>
> NVIDIA (rivafb and nvidiafb) FRAMEBUFFER DRIVER
> diff --git a/drivers/net/can/usb/Kconfig b/drivers/net/can/usb/Kconfig
> index 9dae0c71a2e1..759e724a67cf 100644
> --- a/drivers/net/can/usb/Kconfig
> +++ b/drivers/net/can/usb/Kconfig
> @@ -133,6 +133,17 @@ config CAN_MCBA_USB
> This driver supports the CAN BUS Analyzer interface
> from Microchip (http://www.microchip.com/development-tools/).
>
> +config CAN_NCT6694
> + tristate "Nuvoton NCT6694 Socket CANfd support"
> + depends on MFD_NCT6694
> + select CAN_RX_OFFLOAD
> + help
> + If you say yes to this option, support will be included for Nuvoton
> + NCT6694, a USB device to socket CANfd controller.
> +
> + This driver can also be built as a module. If so, the module will
> + be called nct6694_canfd.
> +
> config CAN_PEAK_USB
> tristate "PEAK PCAN-USB/USB Pro interfaces for CAN 2.0b/CAN-FD"
> help
> diff --git a/drivers/net/can/usb/Makefile b/drivers/net/can/usb/Makefile
> index 8b11088e9a59..fcafb1ac262e 100644
> --- a/drivers/net/can/usb/Makefile
> +++ b/drivers/net/can/usb/Makefile
> @@ -11,5 +11,6 @@ obj-$(CONFIG_CAN_F81604) += f81604.o
> obj-$(CONFIG_CAN_GS_USB) += gs_usb.o
> obj-$(CONFIG_CAN_KVASER_USB) += kvaser_usb/
> obj-$(CONFIG_CAN_MCBA_USB) += mcba_usb.o
> +obj-$(CONFIG_CAN_NCT6694) += nct6694_canfd.o
> obj-$(CONFIG_CAN_PEAK_USB) += peak_usb/
> obj-$(CONFIG_CAN_UCAN) += ucan.o
> diff --git a/drivers/net/can/usb/nct6694_canfd.c b/drivers/net/can/usb/nct6694_canfd.c
> new file mode 100644
> index 000000000000..56d729b438f3
> --- /dev/null
> +++ b/drivers/net/can/usb/nct6694_canfd.c
> @@ -0,0 +1,813 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Nuvoton NCT6694 Socket CANfd driver based on USB interface.
> + *
> + * Copyright (C) 2024 Nuvoton Technology Corp.
> + */
> +
> +#include <linux/can/dev.h>
> +#include <linux/can/rx-offload.h>
> +#include <linux/ethtool.h>
> +#include <linux/irqdomain.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/core.h>
> +#include <linux/mfd/nct6694.h>
> +#include <linux/module.h>
> +#include <linux/netdevice.h>
> +#include <linux/platform_device.h>
> +
> +#define DRVNAME "nct6694_canfd"
> +
> +/*
> + * USB command module type for NCT6694 CANfd controller.
> + * This defines the module type used for communication with the NCT6694
> + * CANfd controller over the USB interface.
> + */
> +#define NCT6694_CAN_MOD 0x05
> +
> +/* Command 00h - CAN Setting and Initialization */
> +#define NCT6694_CAN_SETTING 0x00
> +#define NCT6694_CAN_SETTING_CTRL1_MON BIT(0)
> +#define NCT6694_CAN_SETTING_CTRL1_NISO BIT(1)
> +#define NCT6694_CAN_SETTING_CTRL1_LBCK BIT(2)
> +
> +/* Command 01h - CAN Information */
> +#define NCT6694_CAN_INFORMATION 0x01
> +#define NCT6694_CAN_INFORMATION_SEL 0x00
> +
> +/* Command 02h - CAN Event */
> +#define NCT6694_CAN_EVENT 0x02
> +#define NCT6694_CAN_EVENT_SEL(idx, mask) \
> + ((idx ? 0x80 : 0x00) | ((mask) & 0x7F))
> +
> +#define NCT6694_CAN_EVENT_MASK GENMASK(5, 0)
> +#define NCT6694_CAN_EVT_TX_FIFO_EMPTY BIT(7) /* Read-clear */
> +#define NCT6694_CAN_EVT_RX_DATA_LOST BIT(5) /* Read-clear */
> +#define NCT6694_CAN_EVT_RX_DATA_IN BIT(7) /* Read-clear*/
> +
> +/* Command 10h - CAN Deliver */
> +#define NCT6694_CAN_DELIVER 0x10
> +#define NCT6694_CAN_DELIVER_SEL(buf_cnt) \
> + ((buf_cnt) & 0xFF)
> +
> +/* Command 11h - CAN Receive */
> +#define NCT6694_CAN_RECEIVE 0x11
> +#define NCT6694_CAN_RECEIVE_SEL(idx, buf_cnt) \
> + ((idx ? 0x80 : 0x00) | ((buf_cnt) & 0x7F))
> +
> +#define NCT6694_CAN_FRAME_TAG_CAN0 0xC0
> +#define NCT6694_CAN_FRAME_TAG_CAN1 0xC1
> +#define NCT6694_CAN_FRAME_FLAG_EFF BIT(0)
> +#define NCT6694_CAN_FRAME_FLAG_RTR BIT(1)
> +#define NCT6694_CAN_FRAME_FLAG_FD BIT(2)
> +#define NCT6694_CAN_FRAME_FLAG_BRS BIT(3)
> +#define NCT6694_CAN_FRAME_FLAG_ERR BIT(4)
> +
> +#define NCT6694_NAPI_WEIGHT 32
> +
> +enum nct6694_event_err {
> + NCT6694_CAN_EVT_ERR_NO_ERROR = 0,
> + NCT6694_CAN_EVT_ERR_CRC_ERROR,
> + NCT6694_CAN_EVT_ERR_STUFF_ERROR,
> + NCT6694_CAN_EVT_ERR_ACK_ERROR,
> + NCT6694_CAN_EVT_ERR_FORM_ERROR,
> + NCT6694_CAN_EVT_ERR_BIT_ERROR,
> + NCT6694_CAN_EVT_ERR_TIMEOUT_ERROR,
> + NCT6694_CAN_EVT_ERR_UNKNOWN_ERROR,
> +};
> +
> +enum nct6694_event_status {
> + NCT6694_CAN_EVT_STS_ERROR_ACTIVE = 0,
> + NCT6694_CAN_EVT_STS_ERROR_PASSIVE,
> + NCT6694_CAN_EVT_STS_BUS_OFF,
> + NCT6694_CAN_EVT_STS_WARNING,
> +};
> +
> +struct __packed nct6694_can_setting {
> + __le32 nbr;
> + __le32 dbr;
> + u8 active;
> + u8 reserved[3];
> + __le16 ctrl1;
> + __le16 ctrl2;
> + __le32 nbtp;
> + __le32 dbtp;
> +};
> +
> +struct __packed nct6694_can_information {
> + u8 tx_fifo_cnt;
> + u8 rx_fifo_cnt;
> + u8 reserved[2];
> + __le32 can_clk;
> +};
> +
> +struct __packed nct6694_can_event {
> + u8 err;
> + u8 status;
> + u8 tx_evt;
> + u8 rx_evt;
> + u8 rec;
> + u8 tec;
> + u8 reserved[2];
> +};
> +
> +struct __packed nct6694_can_frame {
> + u8 tag;
> + u8 flag;
> + u8 reserved;
> + u8 length;
> + __le32 id;
> + u8 data[CANFD_MAX_DLEN];
> +};
> +
> +struct nct6694_can_priv {
> + struct can_priv can; /* must be the first member */
> + struct can_rx_offload offload;
> + struct can_berr_counter bec;
> + struct net_device *ndev;
> + struct nct6694 *nct6694;
> + struct workqueue_struct *wq;
> + struct work_struct tx_work;
> + struct nct6694_can_frame tx;
> + struct nct6694_can_frame rx;
> + struct nct6694_can_event event[2];
> + unsigned char can_idx;
> +};

Move the bec to the end just before the can_idx, like this:

struct nct6694_can_priv {
struct can_priv can; /* must be the first member */
struct can_rx_offload offload;
struct net_device *ndev;
struct nct6694 *nct6694;
struct workqueue_struct *wq;
struct work_struct tx_work;
struct nct6694_can_frame tx;
struct nct6694_can_frame rx;
struct nct6694_can_event event[2];
struct can_berr_counter bec;
unsigned char can_idx;
};

For what it is worth, it will save you eight bytes.

Before:

$ pahole -C nct6694_can_priv drivers/net/can/usb/nct6694_canfd.o
struct nct6694_can_priv {
struct can_priv can; /* 0 368 */

/* XXX last struct has 1 hole */

/* --- cacheline 5 boundary (320 bytes) was 48 bytes ago --- */
struct can_rx_offload offload __attribute__((__aligned__(8)));
/* 368 520 */

/* XXX last struct has 7 bytes of padding, 1 hole */

/* --- cacheline 13 boundary (832 bytes) was 56 bytes ago --- */
struct can_berr_counter bec; /* 888 4 */

/* XXX 4 bytes hole, try to pack */

/* --- cacheline 14 boundary (896 bytes) --- */
struct net_device * ndev; /* 896 8 */
struct nct6694 * nct6694; /* 904 8 */
struct workqueue_struct * wq; /* 912 8 */
struct work_struct tx_work; /* 920 32 */
struct nct6694_can_frame tx; /* 952 72 */
/* --- cacheline 16 boundary (1024 bytes) --- */
struct nct6694_can_frame rx; /* 1024 72 */
/* --- cacheline 17 boundary (1088 bytes) was 8 bytes ago --- */
struct nct6694_can_event event[2]; /* 1096 16 */
unsigned char can_idx; /* 1112 1 */

/* size: 1120, cachelines: 18, members: 11 */
/* sum members: 1109, holes: 1, sum holes: 4 */
/* padding: 7 */
/* member types with holes: 2, total: 2 */
/* paddings: 1, sum paddings: 7 */
/* forced alignments: 1 */
/* last cacheline: 32 bytes */
} __attribute__((__aligned__(8)));

After:

$ pahole -C nct6694_can_priv drivers/net/can/usb/nct6694_canfd.o
struct nct6694_can_priv {
struct can_priv can; /* 0 368 */

/* XXX last struct has 1 hole */

/* --- cacheline 5 boundary (320 bytes) was 48 bytes ago --- */
struct can_rx_offload offload __attribute__((__aligned__(8)));
/* 368 520 */

/* XXX last struct has 7 bytes of padding, 1 hole */

/* --- cacheline 13 boundary (832 bytes) was 56 bytes ago --- */
struct net_device * ndev; /* 888 8 */
/* --- cacheline 14 boundary (896 bytes) --- */
struct nct6694 * nct6694; /* 896 8 */
struct workqueue_struct * wq; /* 904 8 */
struct work_struct tx_work; /* 912 32 */
struct nct6694_can_frame tx; /* 944 72 */
/* --- cacheline 15 boundary (960 bytes) was 56 bytes ago --- */
struct nct6694_can_frame rx; /* 1016 72 */
/* --- cacheline 17 boundary (1088 bytes) --- */
struct nct6694_can_event event[2]; /* 1088 16 */
struct can_berr_counter bec; /* 1104 4 */
unsigned char can_idx; /* 1108 1 */

/* size: 1112, cachelines: 18, members: 11 */
/* padding: 3 */
/* member types with holes: 2, total: 2 */
/* paddings: 1, sum paddings: 7 */
/* forced alignments: 1 */
/* last cacheline: 24 bytes */
} __attribute__((__aligned__(8)));

> +static inline struct nct6694_can_priv *rx_offload_to_priv(struct can_rx_offload *offload)
> +{
> + return container_of(offload, struct nct6694_can_priv, offload);
> +}
> +
> +static const struct can_bittiming_const nct6694_can_bittiming_nominal_const = {
> + .name = DRVNAME,
> + .tseg1_min = 2,
> + .tseg1_max = 256,
> + .tseg2_min = 2,
> + .tseg2_max = 128,
> + .sjw_max = 128,
> + .brp_min = 1,
> + .brp_max = 511,
> + .brp_inc = 1,
> +};
> +
> +static const struct can_bittiming_const nct6694_can_bittiming_data_const = {
> + .name = DRVNAME,
> + .tseg1_min = 1,
> + .tseg1_max = 32,
> + .tseg2_min = 1,
> + .tseg2_max = 16,
> + .sjw_max = 16,
> + .brp_min = 1,
> + .brp_max = 31,
> + .brp_inc = 1,
> +};
> +
> +static void nct6694_can_rx_offload(struct can_rx_offload *offload,
> + struct sk_buff *skb)
> +{
> + struct nct6694_can_priv *priv = rx_offload_to_priv(offload);
> + int ret;
> +
> + ret = can_rx_offload_queue_tail(offload, skb);
> + if (ret)
> + priv->ndev->stats.rx_fifo_errors++;
> +}
> +
> +static void nct6694_can_handle_lost_msg(struct net_device *ndev)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> + struct net_device_stats *stats = &ndev->stats;
> + struct can_frame *cf;
> + struct sk_buff *skb;
> +
> + netdev_err(ndev, "RX FIFO overflow, message(s) lost.\n");
> +
> + stats->rx_errors++;
> + stats->rx_over_errors++;
> +
> + skb = alloc_can_err_skb(ndev, &cf);
> + if (!skb)
> + return;
> +
> + cf->can_id |= CAN_ERR_CRTL;
> + cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
> +
> + nct6694_can_rx_offload(&priv->offload, skb);
> +}
> +
> +static void nct6694_can_rx(struct net_device *ndev, u8 rx_evt)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> + struct nct6694_can_frame *frame = &priv->rx;
> + struct nct6694_cmd_header cmd_hd = {
> + .mod = NCT6694_CAN_MOD,
> + .cmd = NCT6694_CAN_RECEIVE,
> + .sel = NCT6694_CAN_RECEIVE_SEL(priv->can_idx, 1),
> + .len = cpu_to_le16(sizeof(*frame))
> + };
> + struct sk_buff *skb;
> + int ret;
> +
> + ret = nct6694_read_msg(priv->nct6694, &cmd_hd, frame);
> + if (ret)
> + return;
> +
> + if (frame->flag & NCT6694_CAN_FRAME_FLAG_FD) {
> + struct canfd_frame *cfd;
> +
> + skb = alloc_canfd_skb(priv->ndev, &cfd);
> + if (!skb)
> + return;
> +
> + cfd->can_id = le32_to_cpu(frame->id);
> + cfd->len = canfd_sanitize_len(frame->length);
> + if (frame->flag & NCT6694_CAN_FRAME_FLAG_EFF)
> + cfd->can_id |= CAN_EFF_FLAG;
> + if (frame->flag & NCT6694_CAN_FRAME_FLAG_BRS)
> + cfd->flags |= CANFD_BRS;
> + if (frame->flag & NCT6694_CAN_FRAME_FLAG_ERR)
> + cfd->flags |= CANFD_ESI;
> +
> + memcpy(cfd->data, frame->data, cfd->len);
> + } else {
> + struct can_frame *cf;
> +
> + skb = alloc_can_skb(priv->ndev, &cf);
> + if (!skb)
> + return;
> +
> + cf->can_id = le32_to_cpu(frame->id);
> + cf->len = canfd_sanitize_len(frame->length);

canfd_sanitize_len() is for canfd. And while writting this I realize
that we do not have a function to sanitize the CAN length… Well, you can
just do:

cf->len = min_t(u8, frame->length, CAN_MAX_DLEN);

Maybe I will all a can_cc_sanitize_len() in the future. It should be the
same definition as can_cc_dlc2len() anyway.

> + if (frame->flag & NCT6694_CAN_FRAME_FLAG_EFF)
> + cf->can_id |= CAN_EFF_FLAG;
> +
> + if (frame->flag & NCT6694_CAN_FRAME_FLAG_RTR)
> + cf->can_id |= CAN_RTR_FLAG;
> + else
> + memcpy(cf->data, frame->data, cf->len);
> + }
> +
> + nct6694_can_rx_offload(&priv->offload, skb);
> +}
> +
> +static int nct6694_can_get_berr_counter(const struct net_device *ndev,
> + struct can_berr_counter *bec)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> +
> + bec->txerr = priv->bec.txerr;
> + bec->rxerr = priv->bec.rxerr;

Nitpick, directly copy the full structure:

*bec = priv->bec;

> +
> + return 0;
> +}
> +
> +static void nct6694_can_handle_state_change(struct net_device *ndev,
> + enum can_state new_state)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> + struct can_berr_counter bec;
> + struct can_frame *cf;
> + struct sk_buff *skb;
> +
> + switch (new_state) {
> + case CAN_STATE_ERROR_ACTIVE:
> + priv->can.can_stats.error_warning++;
> + priv->can.state = CAN_STATE_ERROR_ACTIVE;

Add:

if (cf)
cf->data[1] |= CAN_ERR_CRTL_ACTIVE;

Of course, you will need to adjust the function so that this part occurs
after the skb allocation.

> + break;
> + case CAN_STATE_ERROR_WARNING:
> + priv->can.can_stats.error_warning++;
> + priv->can.state = CAN_STATE_ERROR_WARNING;
> + break;
> + case CAN_STATE_ERROR_PASSIVE:
> + priv->can.can_stats.error_passive++;
> + priv->can.state = CAN_STATE_ERROR_PASSIVE;
> + break;
> + case CAN_STATE_BUS_OFF:
> + priv->can.state = CAN_STATE_BUS_OFF;
> + priv->can.can_stats.bus_off++;
> + can_free_echo_skb(ndev, 0, NULL);
> + netif_stop_queue(ndev);
> + can_bus_off(ndev);
> + break;

Same as above. Here, you need this:

if (cf)
cf->can_id |= CAN_ERR_BUSOFF;

> + default:
> + break;
> + }
> +
> + skb = alloc_can_err_skb(ndev, &cf);
> +
> + nct6694_can_get_berr_counter(ndev, &bec);
> +
> + switch (new_state) {

Why are you doing this

switch (new_state) {

twice? It is confusing. Merge the two toggether and make sure that cf is
correctly updated for each case.

> + case CAN_STATE_ERROR_WARNING:
> + cf->can_id |= CAN_ERR_CRTL;
> + if (bec.txerr > bec.rxerr)
> + cf->data[1] = CAN_ERR_CRTL_TX_WARNING;
> + else
> + cf->data[1] = CAN_ERR_CRTL_RX_WARNING;
> + cf->data[6] = bec.txerr;
> + cf->data[7] = bec.rxerr;

alloc_can_err_skb() may fail. You need a guard to prevent a NULL pointer
dereference:

if (cf) {
cf->can_id |= CAN_ERR_CRTL;
cf->data[6] = bec.txerr;
cf->data[7] = bec.rxerr;
}

> + break;
> + case CAN_STATE_ERROR_PASSIVE:
> + cf->can_id |= CAN_ERR_CRTL;
> + cf->data[1] |= CAN_ERR_CRTL_RX_PASSIVE;
> + if (bec.txerr > 127)

Use the CAN_ERROR_PASSIVE_THRESHOLD macro:

if (bec.txerr >= CAN_ERROR_PASSIVE_THRESHOLD)

> + cf->data[1] |= CAN_ERR_CRTL_TX_PASSIVE;
> + cf->data[6] = bec.txerr;
> + cf->data[7] = bec.rxerr;

Ditto: check that cf is not NULL.

> + break;
> + case CAN_STATE_BUS_OFF:
> + cf->can_id |= CAN_ERR_BUSOFF;.

Same.

> + break;
> + default:
> + break;
> + }
> +
> + nct6694_can_rx_offload(&priv->offload, skb);
> +}
> +
> +static void nct6694_can_handle_state_errors(struct net_device *ndev, u8 status)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> +
> + if (status == NCT6694_CAN_EVT_STS_ERROR_ACTIVE &&
> + priv->can.state != CAN_STATE_ERROR_ACTIVE) {
> + netdev_dbg(ndev, "Error, entered active state\n");
> + nct6694_can_handle_state_change(ndev, CAN_STATE_ERROR_ACTIVE);
> + }
> +
> + if (status == NCT6694_CAN_EVT_STS_WARNING &&
> + priv->can.state != CAN_STATE_ERROR_WARNING) {
> + netdev_dbg(ndev, "Error, entered warning state\n");
> + nct6694_can_handle_state_change(ndev, CAN_STATE_ERROR_WARNING);
> + }
> +
> + if (status == NCT6694_CAN_EVT_STS_ERROR_PASSIVE &&
> + priv->can.state != CAN_STATE_ERROR_PASSIVE) {
> + netdev_dbg(ndev, "Error, entered passive state\n");
> + nct6694_can_handle_state_change(ndev, CAN_STATE_ERROR_PASSIVE);
> + }
> +
> + if (status == NCT6694_CAN_EVT_STS_BUS_OFF &&
> + priv->can.state != CAN_STATE_BUS_OFF) {
> + netdev_dbg(ndev, "Error, entered bus-off state\n");
> + nct6694_can_handle_state_change(ndev, CAN_STATE_BUS_OFF);
> + }
> +}
> +
> +static void nct6694_can_handle_bus_err(struct net_device *ndev, u8 bus_err)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> + struct can_frame *cf;
> + struct sk_buff *skb;
> +
> + if (bus_err == NCT6694_CAN_EVT_ERR_NO_ERROR)
> + return;
> +
> + priv->can.can_stats.bus_error++;
> +
> + skb = alloc_can_err_skb(ndev, &cf);
> + if (skb)
> + cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
> +
> + switch (bus_err) {
> + case NCT6694_CAN_EVT_ERR_CRC_ERROR:
> + netdev_dbg(ndev, "CRC error\n");
> + ndev->stats.rx_errors++;
> + if (skb)
> + cf->data[3] |= CAN_ERR_PROT_LOC_CRC_SEQ;
> + break;
> +
> + case NCT6694_CAN_EVT_ERR_STUFF_ERROR:
> + netdev_dbg(ndev, "Stuff error\n");
> + ndev->stats.rx_errors++;
> + if (skb)
> + cf->data[2] |= CAN_ERR_PROT_STUFF;
> + break;
> +
> + case NCT6694_CAN_EVT_ERR_ACK_ERROR:
> + netdev_dbg(ndev, "Ack error\n");
> + ndev->stats.tx_errors++;
> + if (skb) {
> + cf->can_id |= CAN_ERR_ACK;
> + cf->data[2] |= CAN_ERR_PROT_TX;
> + }
> + break;
> +
> + case NCT6694_CAN_EVT_ERR_FORM_ERROR:
> + netdev_dbg(ndev, "Form error\n");
> + ndev->stats.rx_errors++;
> + if (skb)
> + cf->data[2] |= CAN_ERR_PROT_FORM;
> + break;
> +
> + case NCT6694_CAN_EVT_ERR_BIT_ERROR:
> + netdev_dbg(ndev, "Bit error\n");
> + ndev->stats.tx_errors++;
> + if (skb)
> + cf->data[2] |= CAN_ERR_PROT_TX | CAN_ERR_PROT_BIT;
> + break;
> +
> + default:
> + break;
> + }
> +
> + nct6694_can_rx_offload(&priv->offload, skb);
> +}
> +
> +static void nct6694_can_tx_irq(struct net_device *ndev)
> +{
> + struct net_device_stats *stats = &ndev->stats;
> +
> + stats->tx_bytes += can_get_echo_skb(ndev, 0, NULL);
> + stats->tx_packets++;
> + netif_wake_queue(ndev);
> +}
> +
> +static irqreturn_t nct6694_can_irq(int irq, void *data)
> +{
> + struct net_device *ndev = data;
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> + struct nct6694_can_event *evt = priv->event;
> + struct nct6694_cmd_header cmd_hd = {
> + .mod = NCT6694_CAN_MOD,
> + .cmd = NCT6694_CAN_EVENT,
> + .sel = NCT6694_CAN_EVENT_SEL(priv->can_idx, NCT6694_CAN_EVENT_MASK),
> + .len = cpu_to_le16(sizeof(priv->event))
> + };
> + irqreturn_t handled = IRQ_NONE;
> + int can_idx = priv->can_idx;
> + int ret;
> +
> + ret = nct6694_read_msg(priv->nct6694, &cmd_hd, evt);
> + if (ret < 0)
> + return handled;
> +
> + if (priv->event[can_idx].rx_evt & NCT6694_CAN_EVT_RX_DATA_IN) {
> + nct6694_can_rx(ndev, priv->event[can_idx].rx_evt);
> + handled = IRQ_HANDLED;
> + }
> +
> + if (priv->event[can_idx].rx_evt & NCT6694_CAN_EVT_RX_DATA_LOST) {
> + nct6694_can_handle_lost_msg(ndev);
> + handled = IRQ_HANDLED;
> + }
> +
> + if (priv->event[can_idx].status) {
> + nct6694_can_handle_state_errors(ndev, priv->event[can_idx].status);
> + handled = IRQ_HANDLED;
> + }
> +
> + if (priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING) {
> + nct6694_can_handle_bus_err(ndev, priv->event[can_idx].err);
> + handled = IRQ_HANDLED;
> + }
> +
> + if (handled)
> + can_rx_offload_threaded_irq_finish(&priv->offload);
> +
> + if (priv->event[can_idx].tx_evt & NCT6694_CAN_EVT_TX_FIFO_EMPTY)
> + nct6694_can_tx_irq(ndev);
> +
> + priv->bec.rxerr = priv->event[can_idx].rec;
> + priv->bec.txerr = priv->event[can_idx].tec;
> +
> + return handled;
> +}
> +
> +static void nct6694_can_tx_work(struct work_struct *work)
> +{
> + struct nct6694_can_priv *priv = container_of(work,
> + struct nct6694_can_priv,
> + tx_work);
> + struct nct6694_can_frame *frame = &priv->tx;
> + struct nct6694_cmd_header cmd_hd = {
> + .mod = NCT6694_CAN_MOD,
> + .cmd = NCT6694_CAN_DELIVER,
> + .sel = NCT6694_CAN_DELIVER_SEL(1),
> + .len = cpu_to_le16(sizeof(*frame))
> + };
> + struct net_device *ndev = priv->ndev;
> + struct net_device_stats *stats = &ndev->stats;
> + struct sk_buff *skb = priv->can.echo_skb[0];
> + u32 txid;
> + int err;
> +
> + memset(frame, 0, sizeof(*frame));
> +
> + if (priv->can_idx == 0)
> + frame->tag = NCT6694_CAN_FRAME_TAG_CAN0;
> + else
> + frame->tag = NCT6694_CAN_FRAME_TAG_CAN1;
> +
> + if (can_is_canfd_skb(skb)) {
> + struct canfd_frame *cfd = (struct canfd_frame *)skb->data;
> +
> + if (cfd->flags & CANFD_BRS)
> + frame->flag |= NCT6694_CAN_FRAME_FLAG_BRS;
> +
> + if (cfd->can_id & CAN_EFF_FLAG) {
> + txid = cfd->can_id & CAN_EFF_MASK;
> + frame->flag |= NCT6694_CAN_FRAME_FLAG_EFF;
> + } else {
> + txid = cfd->can_id & CAN_SFF_MASK;
> + }
> + frame->flag |= NCT6694_CAN_FRAME_FLAG_FD;
> + frame->id = cpu_to_le32(txid);
> + frame->length = cfd->len;
> +
> + memcpy(frame->data, cfd->data, cfd->len);
> + } else {
> + struct can_frame *cf = (struct can_frame *)skb->data;
> +
> + if (cf->can_id & CAN_EFF_FLAG) {
> + txid = cf->can_id & CAN_EFF_MASK;
> + frame->flag |= NCT6694_CAN_FRAME_FLAG_EFF;
> + } else {
> + txid = cf->can_id & CAN_SFF_MASK;
> + }
> +
> + if (cf->can_id & CAN_RTR_FLAG)
> + frame->flag |= NCT6694_CAN_FRAME_FLAG_RTR;
> + else
> + memcpy(frame->data, cf->data, cf->len);
> +
> + frame->id = cpu_to_le32(txid);
> + frame->length = cf->len;
> + }
> +
> + err = nct6694_write_msg(priv->nct6694, &cmd_hd, frame);
> + if (err) {
> + netdev_err(ndev, "%s: TX FIFO is full!\n", __func__);
> + can_free_echo_skb(ndev, 0, NULL);
> + stats->tx_dropped++;
> + stats->tx_errors++;
> + netif_wake_queue(ndev);
> + }
> +}
> +
> +static netdev_tx_t nct6694_can_start_xmit(struct sk_buff *skb,
> + struct net_device *ndev)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> +
> + if (can_dev_dropped_skb(ndev, skb))
> + return NETDEV_TX_OK;
> +
> + netif_stop_queue(ndev);
> + can_put_echo_skb(skb, ndev, 0, 0);
> + queue_work(priv->wq, &priv->tx_work);
> +
> + return NETDEV_TX_OK;
> +}
> +
> +static int nct6694_can_start(struct net_device *ndev)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> + struct nct6694_can_setting *setting;
> + struct nct6694_cmd_header cmd_hd = {
> + .mod = NCT6694_CAN_MOD,
> + .cmd = NCT6694_CAN_SETTING,
> + .sel = priv->can_idx,
> + .len = cpu_to_le16(sizeof(*setting))
> + };
> + const struct can_bittiming *n_bt = &priv->can.bittiming;
> + const struct can_bittiming *d_bt = &priv->can.data_bittiming;
> + int ret;
> +
> + setting = kzalloc(sizeof(*setting), GFP_KERNEL);
> + if (!setting)
> + return -ENOMEM;
> +
> + setting->nbr = cpu_to_le32(n_bt->bitrate);
> + setting->dbr = cpu_to_le32(d_bt->bitrate);
> +
> + if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)
> + setting->ctrl1 |= cpu_to_le16(NCT6694_CAN_SETTING_CTRL1_MON);
> +
> + if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) &&
> + priv->can.ctrlmode & CAN_CTRLMODE_FD_NON_ISO)
> + setting->ctrl1 |= cpu_to_le16(NCT6694_CAN_SETTING_CTRL1_NISO);
> +
> + if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
> + setting->ctrl1 |= cpu_to_le16(NCT6694_CAN_SETTING_CTRL1_LBCK);
> +
> + ret = nct6694_write_msg(priv->nct6694, &cmd_hd, setting);
> + if (ret)
> + goto exit;
> +
> + priv->can.state = CAN_STATE_ERROR_ACTIVE;
> +
> +exit:
> + kfree(setting);
> + return ret;
> +}
> +
> +static int nct6694_can_stop(struct net_device *ndev)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> +
> + netif_stop_queue(ndev);
> + free_irq(ndev->irq, ndev);
> + destroy_workqueue(priv->wq);
> + priv->wq = NULL;
> + priv->can.state = CAN_STATE_STOPPED;
> + can_rx_offload_disable(&priv->offload);
> + close_candev(ndev);
> +
> + return 0;
> +}
> +
> +static int nct6694_can_set_mode(struct net_device *ndev, enum can_mode mode)
> +{
> + switch (mode) {
> + case CAN_MODE_START:
> + nct6694_can_start(ndev);
> + netif_wake_queue(ndev);
> + return 0;
> + default:
> + return -EOPNOTSUPP;
> + }
> +}
> +
> +static int nct6694_can_open(struct net_device *ndev)
> +{
> + struct nct6694_can_priv *priv = netdev_priv(ndev);
> + int ret;
> +
> + ret = open_candev(ndev);
> + if (ret)
> + return ret;
> +
> + can_rx_offload_enable(&priv->offload);
> +
> + ret = request_threaded_irq(ndev->irq, NULL,
> + nct6694_can_irq, IRQF_ONESHOT,
> + "nct6694_can", ndev);
> + if (ret) {
> + netdev_err(ndev, "Failed to request IRQ\n");
> + goto close_candev;
> + }
> +
> + priv->wq = alloc_ordered_workqueue("%s-nct6694_wq",
> + WQ_FREEZABLE | WQ_MEM_RECLAIM,
> + ndev->name);
> + if (!priv->wq) {
> + ret = -ENOMEM;
> + goto free_irq;
> + }
> +
> + ret = nct6694_can_start(ndev);
> + if (ret)
> + goto destroy_wq;
> +
> + netif_start_queue(ndev);
> +
> + return 0;
> +
> +destroy_wq:
> + destroy_workqueue(priv->wq);
> +free_irq:
> + free_irq(ndev->irq, ndev);
> +close_candev:
> + can_rx_offload_disable(&priv->offload);
> + close_candev(ndev);
> + return ret;
> +}
> +
> +static const struct net_device_ops nct6694_can_netdev_ops = {
> + .ndo_open = nct6694_can_open,
> + .ndo_stop = nct6694_can_stop,
> + .ndo_start_xmit = nct6694_can_start_xmit,
> + .ndo_change_mtu = can_change_mtu,
> +};
> +
> +static const struct ethtool_ops nct6694_can_ethtool_ops = {
> + .get_ts_info = ethtool_op_get_ts_info,
> +};
> +
> +static int nct6694_can_get_clock(struct nct6694_can_priv *priv)
> +{
> + struct nct6694_can_information *info;
> + struct nct6694_cmd_header cmd_hd = {

If the variable only has constant initializer, make it static const:

static const struct nct6694_cmd_header cmd_hd = {

Apply this at other locations in your different modules.

> + .mod = NCT6694_CAN_MOD,
> + .cmd = NCT6694_CAN_INFORMATION,
> + .sel = NCT6694_CAN_INFORMATION_SEL,
> + .len = cpu_to_le16(sizeof(*info))
> + };
> + int ret, can_clk;
> +
> + info = kzalloc(sizeof(*info), GFP_KERNEL);
> + if (!info)
> + return -ENOMEM;
> +
> + ret = nct6694_read_msg(priv->nct6694, &cmd_hd, info);
> + if (ret)

As pointed by Simon, return an error message here.

> + goto exit;
> +
> + can_clk = le32_to_cpu(info->can_clk);
> +
> +exit:
> + kfree(info);
> + return can_clk;
> +}
> +
> +static int nct6694_can_probe(struct platform_device *pdev)
> +{
> + const struct mfd_cell *cell = mfd_get_cell(pdev);
> + struct nct6694 *nct6694 = dev_get_drvdata(pdev->dev.parent);
> + struct nct6694_can_priv *priv;
> + struct net_device *ndev;
> + int ret, irq, can_clk;
> +
> + irq = irq_create_mapping(nct6694->domain,
> + NCT6694_IRQ_CAN1 + cell->id);
> + if (!irq)
> + return irq;
> +
> + ndev = alloc_candev(sizeof(struct nct6694_can_priv), 1);
> + if (!ndev)
> + return -ENOMEM;
> +
> + ndev->irq = irq;
> + ndev->flags |= IFF_ECHO;
> + ndev->dev_port = cell->id;
> + ndev->netdev_ops = &nct6694_can_netdev_ops;
> + ndev->ethtool_ops = &nct6694_can_ethtool_ops;
> +
> + priv = netdev_priv(ndev);
> + priv->nct6694 = nct6694;
> + priv->ndev = ndev;
> +
> + can_clk = nct6694_can_get_clock(priv);
> + if (can_clk < 0) {
> + ret = dev_err_probe(&pdev->dev, can_clk,
> + "Failed to get clock\n");
> + goto free_candev;
> + }
> +
> + INIT_WORK(&priv->tx_work, nct6694_can_tx_work);
> +
> + priv->can_idx = cell->id;
> + priv->can.state = CAN_STATE_STOPPED;
> + priv->can.clock.freq = can_clk;
> + priv->can.bittiming_const = &nct6694_can_bittiming_nominal_const;
> + priv->can.data_bittiming_const = &nct6694_can_bittiming_data_const;
> + priv->can.do_set_mode = nct6694_can_set_mode;
> + priv->can.do_get_berr_counter = nct6694_can_get_berr_counter;
> +
> + priv->can.ctrlmode = CAN_CTRLMODE_FD;
> +
> + priv->can.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK |
> + CAN_CTRLMODE_LISTENONLY |
> + CAN_CTRLMODE_FD |
> + CAN_CTRLMODE_FD_NON_ISO |
> + CAN_CTRLMODE_BERR_REPORTING;
> +
> + ret = can_rx_offload_add_manual(ndev, &priv->offload,
> + NCT6694_NAPI_WEIGHT);
> + if (ret) {
> + dev_err_probe(&pdev->dev, ret, "Failed to add rx_offload\n");
> + goto free_candev;
> + }
> +
> + platform_set_drvdata(pdev, priv);
> + SET_NETDEV_DEV(priv->ndev, &pdev->dev);
> +
> + ret = register_candev(priv->ndev);
> + if (ret)
> + goto del_rx_offload;
> +
> + return 0;
> +
> +del_rx_offload:
> + can_rx_offload_del(&priv->offload);
> +free_candev:
> + free_candev(ndev);
> + return ret;
> +}
> +
> +static void nct6694_can_remove(struct platform_device *pdev)
> +{
> + struct nct6694_can_priv *priv = platform_get_drvdata(pdev);
> +
> + cancel_work_sync(&priv->tx_work);
> + unregister_candev(priv->ndev);
> + can_rx_offload_del(&priv->offload);
> + free_candev(priv->ndev);
> +}
> +
> +static struct platform_driver nct6694_can_driver = {
> + .driver = {
> + .name = DRVNAME,
> + },
> + .probe = nct6694_can_probe,
> + .remove = nct6694_can_remove,
> +};
> +
> +module_platform_driver(nct6694_can_driver);
> +
> +MODULE_DESCRIPTION("USB-CAN FD driver for NCT6694");
> +MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:nct6694-can");

Yours sincerely,
Vincent Mailhol