[PATCH v3 4/7] can: Add Nuvoton NCT6694 CAN support

[Ming Yu <a0282524688@xxxxxxxxx>]

This driver supports Socket CANfd functionality for NCT6694 MFD
device based on USB interface.

Signed-off-by: Ming Yu <tmyu0@xxxxxxxxxxx>
---
 MAINTAINERS                     |   1 +
 drivers/net/can/Kconfig         |  10 +
 drivers/net/can/Makefile        |   1 +
 drivers/net/can/nct6694_canfd.c | 920 ++++++++++++++++++++++++++++++++
 4 files changed, 932 insertions(+)
 create mode 100644 drivers/net/can/nct6694_canfd.c

diff --git a/MAINTAINERS b/MAINTAINERS
index a190f2b08fa3..eb5d46825e71 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16548,6 +16548,7 @@ S:	Supported
 F:	drivers/gpio/gpio-nct6694.c
 F:	drivers/i2c/busses/i2c-nct6694.c
 F:	drivers/mfd/nct6694.c
+F:	drivers/net/can/nct6694_canfd.c
 F:	include/linux/mfd/nct6694.h
 
 NVIDIA (rivafb and nvidiafb) FRAMEBUFFER DRIVER
diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
index cf989bea9aa3..130e98ec28a5 100644
--- a/drivers/net/can/Kconfig
+++ b/drivers/net/can/Kconfig
@@ -200,6 +200,16 @@ config CAN_SUN4I
 	  To compile this driver as a module, choose M here: the module will
 	  be called sun4i_can.
 
+config CAN_NCT6694
+	tristate "Nuvoton NCT6694 Socket CANfd support"
+	depends on MFD_NCT6694
+	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_TI_HECC
 	depends on ARM
 	tristate "TI High End CAN Controller"
diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile
index a71db2cfe990..4a6b5b9d6c2b 100644
--- a/drivers/net/can/Makefile
+++ b/drivers/net/can/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_CAN_JANZ_ICAN3)	+= janz-ican3.o
 obj-$(CONFIG_CAN_KVASER_PCIEFD)	+= kvaser_pciefd.o
 obj-$(CONFIG_CAN_MSCAN)		+= mscan/
 obj-$(CONFIG_CAN_M_CAN)		+= m_can/
+obj-$(CONFIG_CAN_NCT6694)	+= nct6694_canfd.o
 obj-$(CONFIG_CAN_PEAK_PCIEFD)	+= peak_canfd/
 obj-$(CONFIG_CAN_SJA1000)	+= sja1000/
 obj-$(CONFIG_CAN_SUN4I)		+= sun4i_can.o
diff --git a/drivers/net/can/nct6694_canfd.c b/drivers/net/can/nct6694_canfd.c
new file mode 100644
index 000000000000..54f20f0681e2
--- /dev/null
+++ b/drivers/net/can/nct6694_canfd.c
@@ -0,0 +1,920 @@
+// 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/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-can"
+
+/* Host interface */
+#define NCT6694_CAN_MOD			0x05
+
+/* Message Channel*/
+/* Command 00h */
+#define NCT6694_CAN_CMD0_OFFSET(idx)	(idx ? 0x0100 : 0x0000)
+#define NCT6694_CAN_CTRL1_MON		BIT(0)
+#define NCT6694_CAN_CTRL1_NISO		BIT(1)
+#define NCT6694_CAN_CTRL1_LBCK		BIT(2)
+
+/* Command 01h */
+#define NCT6694_CAN_CMD1_OFFSET		0x0001
+
+/* Command 02h */
+#define NCT6694_CAN_CMD2_OFFSET(idx, mask)			\
+	({ typeof(mask) mask_ = (mask);				\
+	   idx ? ((0x80 | (mask_ & 0xFF)) << 8 | 0x02) :	\
+		 ((0x00 | (mask_ & 0xFF)) << 8 | 0x02); })
+
+#define NCT6694_CAN_EVENT_ERR		BIT(0)
+#define NCT6694_CAN_EVENT_STATUS	BIT(1)
+#define NCT6694_CAN_EVENT_TX_EVT	BIT(2)
+#define NCT6694_CAN_EVENT_RX_EVT	BIT(3)
+#define NCT6694_CAN_EVENT_REC		BIT(4)
+#define NCT6694_CAN_EVENT_TEC		BIT(5)
+#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_HALF_FULL	BIT(6)	/* Read-clear */
+#define NCT6694_CAN_EVT_RX_DATA_IN	BIT(7)
+
+/* Command 10h */
+#define NCT6694_CAN_CMD10_OFFSET(buf_cnt)	\
+	(((buf_cnt) & 0xFF) << 8 | 0x10)
+#define NCT6694_CAN_TAG_CAN0		0xC0
+#define NCT6694_CAN_TAG_CAN1		0xC1
+#define NCT6694_CAN_FLAG_EFF		BIT(0)
+#define NCT6694_CAN_FLAG_RTR		BIT(1)
+#define NCT6694_CAN_FLAG_FD		BIT(2)
+#define NCT6694_CAN_FLAG_BRS		BIT(3)
+#define NCT6694_CAN_FLAG_ERR		BIT(4)
+
+/* Command 11h */
+#define NCT6694_CAN_CMD11_OFFSET(idx, buf_cnt)			\
+	({ typeof(buf_cnt) buf_cnt_ = (buf_cnt);		\
+	   idx ? ((0x80 | (buf_cnt_ & 0xFF)) << 8 | 0x11) :	\
+		 ((0x00 | (buf_cnt_ & 0xFF)) << 8 | 0x11); })
+
+#define NCT6694_CAN_RX_QUOTA		64
+
+enum nct6694_event_err {
+	NCT6694_CAN_EVT_NO_ERROR,
+	NCT6694_CAN_EVT_CRC_ERROR,
+	NCT6694_CAN_EVT_STUFF_ERROR,
+	NCT6694_CAN_EVT_ACK_ERROR,
+	NCT6694_CAN_EVT_FORM_ERROR,
+	NCT6694_CAN_EVT_BIT_ERROR,
+	NCT6694_CAN_EVT_TIMEOUT_ERROR,
+	NCT6694_CAN_EVT_UNKNOWN_ERROR,
+};
+
+enum nct6694_event_status {
+	NCT6694_CAN_EVT_ERROR_ACTIVE,
+	NCT6694_CAN_EVT_ERROR_PASSIVE,
+	NCT6694_CAN_EVT_BUS_OFF,
+	NCT6694_CAN_EVT_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;
+	__le16 reserved;
+	__le32 can_clk;
+};
+
+struct __packed nct6694_can_event {
+	u8 err1;
+	u8 status1;
+	u8 tx_evt1;
+	u8 rx_evt1;
+	u8 rec1;
+	u8 tec1;
+	u8 reserved1[2];
+	u8 err2;
+	u8 status2;
+	u8 tx_evt2;
+	u8 rx_evt2;
+	u8 rec2;
+	u8 tec2;
+	u8 reserved2[2];
+};
+
+struct __packed nct6694_can_xmit {
+	u8 tag;
+	u8 flag;
+	u8 reserved;
+	u8 dlc;
+	__le32 id;
+	u8 data[64];
+	u8 msg_buf[72];
+};
+
+struct nct6694_can_priv {
+	struct can_priv can;	/* must be the first member */
+	struct net_device *ndev;
+	struct nct6694 *nct6694;
+	struct mutex lock;
+	struct sk_buff *tx_skb;
+	struct workqueue_struct *wq;
+	struct work_struct tx_work;
+	unsigned char *tx_buf;
+	unsigned char *rx_buf;
+	unsigned char can_idx;
+	bool tx_busy;
+};
+
+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_clean(struct net_device *ndev)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+
+	if (priv->tx_skb || priv->tx_busy)
+		ndev->stats.tx_errors++;
+	dev_kfree_skb(priv->tx_skb);
+	if (priv->tx_busy)
+		can_free_echo_skb(priv->ndev, 0, NULL);
+	priv->tx_skb = NULL;
+	priv->tx_busy = false;
+}
+
+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);
+	struct nct6694_can_event *evt = (struct nct6694_can_event *)priv->rx_buf;
+	u8 mask = NCT6694_CAN_EVENT_REC | NCT6694_CAN_EVENT_TEC;
+	int ret;
+
+	guard(mutex)(&priv->lock);
+
+	ret = nct6694_read_msg(priv->nct6694, NCT6694_CAN_MOD,
+			       NCT6694_CAN_CMD2_OFFSET(priv->can_idx, mask),
+			       sizeof(struct nct6694_can_event),
+			       evt);
+	if (ret < 0)
+		return ret;
+
+	bec->rxerr = priv->can_idx ? evt->rec2 : evt->rec1;
+	bec->txerr = priv->can_idx ? evt->tec2 : evt->tec1;
+
+	return 0;
+}
+
+static int nct6694_can_handle_lost_msg(struct net_device *ndev)
+{
+	struct net_device_stats *stats = &ndev->stats;
+	struct sk_buff *skb;
+	struct can_frame *frame;
+
+	netdev_err(ndev, "RX FIFO overflow, message(s) lost.\n");
+
+	stats->rx_errors++;
+	stats->rx_over_errors++;
+
+	skb = alloc_can_err_skb(ndev, &frame);
+	if (unlikely(!skb))
+		return 0;
+
+	frame->can_id |= CAN_ERR_CRTL;
+	frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
+
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
+static void nct6694_can_read_fifo(struct net_device *ndev)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct nct6694_can_xmit *xmit = (struct nct6694_can_xmit *)priv->rx_buf;
+	struct net_device_stats *stats = &ndev->stats;
+	struct canfd_frame *cf;
+	struct sk_buff *skb;
+	int can_idx = priv->can_idx;
+	u32 id;
+	int ret;
+	u8 fd_format = 0;
+
+	guard(mutex)(&priv->lock);
+
+	ret = nct6694_read_msg(priv->nct6694, NCT6694_CAN_MOD,
+			       NCT6694_CAN_CMD11_OFFSET(can_idx, 1),
+			       sizeof(struct nct6694_can_xmit), xmit);
+	if (ret < 0)
+		return;
+
+	/* Check type of frame and create skb */
+	fd_format = xmit->flag & NCT6694_CAN_FLAG_FD;
+	if (fd_format)
+		skb = alloc_canfd_skb(ndev, &cf);
+	else
+		skb = alloc_can_skb(ndev, (struct can_frame **)&cf);
+
+	if (!skb) {
+		stats->rx_dropped++;
+		return;
+	}
+
+	cf->len = xmit->dlc;
+
+	/* Get ID and set flag by its type(Standard ID format or Ext ID format) */
+	id = le32_to_cpu(xmit->id);
+	if (xmit->flag & NCT6694_CAN_FLAG_EFF) {
+		/*
+		 * In case the Extended ID frame is received, the standard
+		 * and extended part of the ID are swapped in the register,
+		 * so swap them back to obtain the correct ID.
+		 */
+		id |= CAN_EFF_FLAG;
+	}
+
+	cf->can_id = id;
+
+	/* Set ESI flag */
+	if (xmit->flag & NCT6694_CAN_FLAG_ERR) {
+		cf->flags |= CANFD_ESI;
+		netdev_dbg(ndev, "ESI Error\n");
+	}
+
+	/* Set RTR and BRS */
+	if (!fd_format && (xmit->flag & NCT6694_CAN_FLAG_RTR)) {
+		cf->can_id |= CAN_RTR_FLAG;
+	} else {
+		if (xmit->flag & NCT6694_CAN_FLAG_BRS)
+			cf->flags |= CANFD_BRS;
+
+		memcpy(cf->data, xmit->data, cf->len);
+
+		stats->rx_bytes += cf->len;
+	}
+
+	stats->rx_packets++;
+
+	netif_receive_skb(skb);
+}
+
+static int nct6694_can_do_rx_poll(struct net_device *ndev, int quota)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct nct6694_can_event *evt = (struct nct6694_can_event *)priv->rx_buf;
+	int can_idx = priv->can_idx;
+	u32 pkts = 0;
+	u8 mask_rx = NCT6694_CAN_EVENT_RX_EVT;
+	u8 rx_evt;
+
+	for (;;) {
+		scoped_guard(mutex, &priv->lock) {
+			nct6694_read_msg(priv->nct6694, NCT6694_CAN_MOD,
+					 NCT6694_CAN_CMD2_OFFSET(can_idx, mask_rx),
+					 sizeof(struct nct6694_can_event), evt);
+
+			rx_evt = can_idx ? evt->rx_evt2 : evt->rx_evt1;
+		}
+
+		if (rx_evt & NCT6694_CAN_EVT_RX_DATA_LOST)
+			nct6694_can_handle_lost_msg(ndev);
+
+		/* No data */
+		if ((rx_evt & NCT6694_CAN_EVT_RX_DATA_IN) == 0)
+			break;
+
+		if (quota <= 0)
+			break;
+
+		nct6694_can_read_fifo(ndev);
+		quota--;
+		pkts++;
+	}
+
+	return pkts;
+}
+
+static int nct6694_can_handle_lec_err(struct net_device *ndev, u8 bus_err)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct net_device_stats *stats = &ndev->stats;
+	struct can_frame *cf;
+	struct sk_buff *skb;
+
+	if (bus_err == NCT6694_CAN_EVT_NO_ERROR)
+		return 0;
+
+	priv->can.can_stats.bus_error++;
+	stats->rx_errors++;
+
+	/* Propagate the error condition to the CAN stack. */
+	skb = alloc_can_err_skb(ndev, &cf);
+
+	if (unlikely(!skb))
+		return 0;
+
+	/* Read the error counter register and check for new errors. */
+	cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
+
+	switch (bus_err) {
+	case NCT6694_CAN_EVT_CRC_ERROR:
+		cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
+		break;
+
+	case NCT6694_CAN_EVT_STUFF_ERROR:
+		cf->data[2] |= CAN_ERR_PROT_STUFF;
+		break;
+
+	case NCT6694_CAN_EVT_ACK_ERROR:
+		cf->data[3] = CAN_ERR_PROT_LOC_ACK;
+		break;
+
+	case NCT6694_CAN_EVT_FORM_ERROR:
+		cf->data[2] |= CAN_ERR_PROT_FORM;
+		break;
+
+	case NCT6694_CAN_EVT_BIT_ERROR:
+		cf->data[2] |= CAN_ERR_PROT_BIT |
+			       CAN_ERR_PROT_BIT0 |
+			       CAN_ERR_PROT_BIT1;
+		break;
+
+	case NCT6694_CAN_EVT_TIMEOUT_ERROR:
+		cf->data[2] |= CAN_ERR_PROT_UNSPEC;
+		break;
+
+	case NCT6694_CAN_EVT_UNKNOWN_ERROR:
+		cf->data[2] |= CAN_ERR_PROT_UNSPEC;
+		/*
+		 * It means 'unspecified'(the value is '0').
+		 * But it is not sure if it's ok to send an error package
+		 * without specific error bit.
+		 */
+		break;
+
+	default:
+		break;
+	}
+
+	/* Reset the error counter, ack the IRQ and re-enable the counter. */
+	stats->rx_packets++;
+	stats->rx_bytes += cf->can_dlc;
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
+static int nct6694_can_handle_state_change(struct net_device *ndev,
+					   enum can_state new_state)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct net_device_stats *stats = &ndev->stats;
+	struct can_frame *cf;
+	struct sk_buff *skb;
+	struct can_berr_counter bec;
+
+	switch (new_state) {
+	case CAN_STATE_ERROR_ACTIVE:
+		priv->can.can_stats.error_warning++;
+		priv->can.state = CAN_STATE_ERROR_ACTIVE;
+		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_bus_off(ndev);
+		break;
+	default:
+		break;
+	}
+
+	/* propagate the error condition to the CAN stack */
+	skb = alloc_can_err_skb(ndev, &cf);
+	if (unlikely(!skb))
+		return 0;
+
+	nct6694_can_get_berr_counter(ndev, &bec);
+
+	switch (new_state) {
+	case CAN_STATE_ERROR_WARNING:
+		/* error warning state */
+		cf->can_id |= CAN_ERR_CRTL;
+		cf->data[1] = (bec.txerr > bec.rxerr) ? CAN_ERR_CRTL_TX_WARNING :
+							CAN_ERR_CRTL_RX_WARNING;
+		cf->data[6] = bec.txerr;
+		cf->data[7] = bec.rxerr;
+		break;
+	case CAN_STATE_ERROR_PASSIVE:
+		/* error passive state */
+		cf->can_id |= CAN_ERR_CRTL;
+		cf->data[1] |= CAN_ERR_CRTL_RX_PASSIVE;
+		if (bec.txerr > 127)
+			cf->data[1] |= CAN_ERR_CRTL_TX_PASSIVE;
+		cf->data[6] = bec.txerr;
+		cf->data[7] = bec.rxerr;
+		break;
+	case CAN_STATE_BUS_OFF:
+		/* bus-off state */
+		cf->can_id |= CAN_ERR_BUSOFF;
+		break;
+	default:
+		break;
+	}
+
+	stats->rx_packets++;
+	stats->rx_bytes += cf->can_dlc;
+	netif_receive_skb(skb);
+
+	return 1;
+}
+
+static int nct6694_can_handle_state_errors(struct net_device *ndev,
+					   unsigned char can_status)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	int work_done = 0;
+
+	if (can_status == NCT6694_CAN_EVT_ERROR_ACTIVE &&
+	    priv->can.state != CAN_STATE_ERROR_ACTIVE) {
+		netdev_dbg(ndev, "Error, entered active state\n");
+		work_done += nct6694_can_handle_state_change(ndev,
+							     CAN_STATE_ERROR_ACTIVE);
+	}
+
+	if (can_status == NCT6694_CAN_EVT_WARNING &&
+	    priv->can.state != CAN_STATE_ERROR_WARNING) {
+		netdev_dbg(ndev, "Error, entered warning state\n");
+		work_done += nct6694_can_handle_state_change(ndev,
+							     CAN_STATE_ERROR_WARNING);
+	}
+
+	if (can_status == NCT6694_CAN_EVT_ERROR_PASSIVE &&
+	    priv->can.state != CAN_STATE_ERROR_PASSIVE) {
+		netdev_dbg(ndev, "Error, entered passive state\n");
+		work_done += nct6694_can_handle_state_change(ndev,
+							     CAN_STATE_ERROR_PASSIVE);
+	}
+
+	if (can_status == NCT6694_CAN_EVT_BUS_OFF &&
+	    priv->can.state != CAN_STATE_BUS_OFF) {
+		netdev_dbg(ndev, "Error, entered bus-off state\n");
+		work_done += nct6694_can_handle_state_change(ndev,
+							     CAN_STATE_BUS_OFF);
+	}
+
+	return work_done;
+}
+
+static int nct6694_can_poll(struct net_device *ndev, int quota)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct nct6694_can_event *evt = (struct nct6694_can_event *)priv->rx_buf;
+	int can_idx = priv->can_idx;
+	int work_done = 0, ret;
+	u8 evt_mask = NCT6694_CAN_EVENT_ERR | NCT6694_CAN_EVENT_STATUS;
+	u8 bus_err, can_status;
+
+	scoped_guard(mutex, &priv->lock) {
+		ret = nct6694_read_msg(priv->nct6694, NCT6694_CAN_MOD,
+				       NCT6694_CAN_CMD2_OFFSET(can_idx, evt_mask),
+				       sizeof(struct nct6694_can_event), evt);
+		if (ret < 0)
+			return IRQ_NONE;
+
+		if (can_idx) {
+			bus_err = evt->err2;
+			can_status = evt->status2;
+		} else {
+			bus_err = evt->err1;
+			can_status = evt->status1;
+		}
+	}
+
+	/* Handle bus state changes */
+	work_done += nct6694_can_handle_state_errors(ndev, can_status);
+
+	/* Handle lec errors on the bus */
+	if (priv->can.ctrlmode & CAN_CTRLMODE_BERR_REPORTING)
+		work_done += nct6694_can_handle_lec_err(ndev, bus_err);
+
+	/* Handle RX events */
+	work_done += nct6694_can_do_rx_poll(ndev, quota - work_done);
+	return work_done;
+}
+
+static void nct6694_can_tx_irq(struct net_device *ndev)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct net_device_stats *stats = &ndev->stats;
+
+	guard(mutex)(&priv->lock);
+	stats->tx_bytes += can_get_echo_skb(ndev, 0, NULL);
+	stats->tx_packets++;
+	priv->tx_busy = false;
+	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 = (struct nct6694_can_event *)priv->rx_buf;
+	int can_idx = priv->can_idx;
+	int ret;
+	u8 mask_sts = NCT6694_CAN_EVENT_TX_EVT;
+	u8 tx_evt;
+
+	scoped_guard(mutex, &priv->lock) {
+		ret = nct6694_read_msg(priv->nct6694, NCT6694_CAN_MOD,
+				       NCT6694_CAN_CMD2_OFFSET(can_idx, mask_sts),
+				       sizeof(struct nct6694_can_event), evt);
+		if (ret < 0)
+			return IRQ_NONE;
+
+		tx_evt = can_idx ? evt->tx_evt2 : evt->tx_evt1;
+	}
+
+	if (tx_evt) {
+		nct6694_can_tx_irq(ndev);
+	} else {
+		ret = nct6694_can_poll(ndev, NCT6694_CAN_RX_QUOTA);
+		if (!ret)
+			return IRQ_NONE;
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int nct6694_can_start(struct net_device *ndev)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct nct6694_can_setting *setting = (struct nct6694_can_setting *)priv->tx_buf;
+	const struct can_bittiming *n_bt = &priv->can.bittiming;
+	const struct can_bittiming *d_bt = &priv->can.data_bittiming;
+	int ret;
+
+	guard(mutex)(&priv->lock);
+
+	memset(priv->tx_buf, 0, sizeof(struct nct6694_can_setting));
+	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_CTRL1_MON);
+
+	if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) &&
+	    priv->can.ctrlmode & CAN_CTRLMODE_FD_NON_ISO)
+		setting->ctrl1 |= cpu_to_le16(NCT6694_CAN_CTRL1_NISO);
+
+	if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK)
+		setting->ctrl1 |= cpu_to_le16(NCT6694_CAN_CTRL1_LBCK);
+
+	ret = nct6694_write_msg(priv->nct6694, NCT6694_CAN_MOD,
+				NCT6694_CAN_CMD0_OFFSET(priv->can_idx),
+				sizeof(struct nct6694_can_setting), setting);
+	if (ret < 0)
+		return ret;
+
+	priv->can.state = CAN_STATE_ERROR_ACTIVE;
+
+	return 0;
+}
+
+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;
+	nct6694_can_clean(ndev);
+	priv->can.state = CAN_STATE_STOPPED;
+	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_clean(ndev);
+		nct6694_can_start(ndev);
+		netif_wake_queue(ndev);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+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;
+
+	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;
+	}
+
+	priv->tx_skb = NULL;
+	priv->tx_busy = false;
+
+	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:
+	close_candev(ndev);
+	return ret;
+}
+
+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 (priv->tx_skb || priv->tx_busy) {
+		netdev_err(ndev, "hard_xmit called while tx busy\n");
+		return NETDEV_TX_BUSY;
+	}
+
+	if (can_dev_dropped_skb(ndev, skb))
+		return NETDEV_TX_OK;
+
+	netif_stop_queue(ndev);
+	priv->tx_skb = skb;
+	queue_work(priv->wq, &priv->tx_work);
+
+	return NETDEV_TX_OK;
+}
+
+static void nct6694_can_tx(struct net_device *ndev, struct canfd_frame *cf)
+{
+	struct nct6694_can_priv *priv = netdev_priv(ndev);
+	struct nct6694_can_xmit *xmit = (struct nct6694_can_xmit *)priv->tx_buf;
+	u32 txid = 0;
+
+	memset(xmit, 0, sizeof(struct nct6694_can_xmit));
+
+	if (priv->can_idx == 0)
+		xmit->tag = NCT6694_CAN_TAG_CAN0;
+	else
+		xmit->tag = NCT6694_CAN_TAG_CAN1;
+
+	if (cf->can_id & CAN_EFF_FLAG) {
+		txid = cf->can_id & CAN_EFF_MASK;
+		/*
+		 * In case the Extended ID frame is transmitted, the
+		 * standard and extended part of the ID are swapped
+		 * in the register, so swap them back to send the
+		 * correct ID.
+		 */
+		xmit->flag |= NCT6694_CAN_FLAG_EFF;
+	} else {
+		txid = cf->can_id & CAN_SFF_MASK;
+	}
+
+	xmit->id = cpu_to_le32(txid);
+	xmit->dlc = cf->len;
+
+	if ((priv->can.ctrlmode & CAN_CTRLMODE_FD) &&
+	    can_is_canfd_skb(priv->tx_skb)) {
+		xmit->flag |= NCT6694_CAN_FLAG_FD;
+		if (cf->flags & CANFD_BRS)
+			xmit->flag |= NCT6694_CAN_FLAG_BRS;
+	}
+
+	if (cf->can_id & CAN_RTR_FLAG)
+		xmit->flag |= NCT6694_CAN_FLAG_RTR;
+
+	memcpy(xmit->data, cf->data, cf->len);
+
+	nct6694_write_msg(priv->nct6694, NCT6694_CAN_MOD,
+			  NCT6694_CAN_CMD10_OFFSET(1),
+			  sizeof(struct nct6694_can_xmit),
+			  xmit);
+}
+
+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 net_device *ndev = priv->ndev;
+	struct canfd_frame *cf;
+
+	guard(mutex)(&priv->lock);
+
+	if (priv->tx_skb) {
+		if (priv->can.state == CAN_STATE_BUS_OFF) {
+			nct6694_can_clean(ndev);
+		} else {
+			cf = (struct canfd_frame *)priv->tx_skb->data;
+			nct6694_can_tx(ndev, cf);
+			priv->tx_busy = true;
+			can_put_echo_skb(priv->tx_skb, ndev, 0, 0);
+			priv->tx_skb = NULL;
+		}
+	}
+}
+
+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_can_information *)priv->rx_buf;
+	int ret;
+
+	ret = nct6694_read_msg(priv->nct6694, NCT6694_CAN_MOD,
+			       NCT6694_CAN_CMD1_OFFSET,
+			       sizeof(struct nct6694_can_information),
+			       info);
+	if (ret)
+		return ret;
+
+	return le32_to_cpu(info->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 -EINVAL;
+
+	ndev = alloc_candev(sizeof(struct nct6694_can_priv), 1);
+	if (!ndev)
+		return -ENOMEM;
+
+	ndev->irq = irq;
+	ndev->flags |= IFF_ECHO;
+	ndev->netdev_ops = &nct6694_can_netdev_ops;
+	ndev->ethtool_ops = &nct6694_can_ethtool_ops;
+
+	priv = netdev_priv(ndev);
+	priv->nct6694 = nct6694;
+	priv->ndev = ndev;
+
+	priv->tx_buf = devm_kcalloc(&pdev->dev, NCT6694_MAX_PACKET_SZ,
+				    sizeof(unsigned char), GFP_KERNEL);
+	if (!priv->tx_buf) {
+		ret = -ENOMEM;
+		goto free_candev;
+	}
+
+	priv->rx_buf = devm_kcalloc(&pdev->dev, NCT6694_MAX_PACKET_SZ,
+				    sizeof(unsigned char), GFP_KERNEL);
+	if (!priv->rx_buf) {
+		ret = -ENOMEM;
+		goto free_candev;
+	}
+
+	can_clk = nct6694_can_get_clock(priv);
+	if (can_clk < 0) {
+		ret = -EIO;
+		goto free_candev;
+	}
+
+	mutex_init(&priv->lock);
+	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;
+
+	platform_set_drvdata(pdev, priv);
+	SET_NETDEV_DEV(priv->ndev, &pdev->dev);
+
+	ret = register_candev(priv->ndev);
+	if (ret)
+		goto free_candev;
+
+	return 0;
+
+free_candev:
+	free_candev(ndev);
+	return dev_err_probe(&pdev->dev, ret, "Probe failed\n");
+}
+
+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);
+	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@xxxxxxxxxxx>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:nct6694-can");
-- 
2.34.1