xref: /openbmc/linux/drivers/net/can/usb/mcba_usb.c (revision 7ae9fb1b7ecbb5d85d07857943f677fd1a559b18)

// SPDX-License-Identifier: GPL-2.0-only
/* SocketCAN driver for Microchip CAN BUS Analyzer Tool
 *
 * Copyright (C) 2017 Mobica Limited
 *
 * This driver is inspired by the 4.6.2 version of net/can/usb/usb_8dev.c
 */

#include <asm/unaligned.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/error.h>
#include <linux/ethtool.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/usb.h>

/* vendor and product id */
#define MCBA_MODULE_NAME "mcba_usb"
#define MCBA_VENDOR_ID 0x04d8
#define MCBA_PRODUCT_ID 0x0a30

/* driver constants */
#define MCBA_MAX_RX_URBS 20
#define MCBA_MAX_TX_URBS 20
#define MCBA_CTX_FREE MCBA_MAX_TX_URBS

/* RX buffer must be bigger than msg size since at the
 * beginning USB messages are stacked.
 */
#define MCBA_USB_RX_BUFF_SIZE 64
#define MCBA_USB_TX_BUFF_SIZE (sizeof(struct mcba_usb_msg))

/* Microchip command id */
#define MBCA_CMD_RECEIVE_MESSAGE 0xE3
#define MBCA_CMD_I_AM_ALIVE_FROM_CAN 0xF5
#define MBCA_CMD_I_AM_ALIVE_FROM_USB 0xF7
#define MBCA_CMD_CHANGE_BIT_RATE 0xA1
#define MBCA_CMD_TRANSMIT_MESSAGE_EV 0xA3
#define MBCA_CMD_SETUP_TERMINATION_RESISTANCE 0xA8
#define MBCA_CMD_READ_FW_VERSION 0xA9
#define MBCA_CMD_NOTHING_TO_SEND 0xFF
#define MBCA_CMD_TRANSMIT_MESSAGE_RSP 0xE2

#define MCBA_VER_REQ_USB 1
#define MCBA_VER_REQ_CAN 2

/* Drive the CAN_RES signal LOW "0" to activate R24 and R25 */
#define MCBA_VER_TERMINATION_ON 0
#define MCBA_VER_TERMINATION_OFF 1

#define MCBA_SIDL_EXID_MASK 0x8
#define MCBA_DLC_MASK 0xf
#define MCBA_DLC_RTR_MASK 0x40

#define MCBA_CAN_STATE_WRN_TH 95
#define MCBA_CAN_STATE_ERR_PSV_TH 127

#define MCBA_TERMINATION_DISABLED CAN_TERMINATION_DISABLED
#define MCBA_TERMINATION_ENABLED 120

struct mcba_usb_ctx {
	struct mcba_priv *priv;
	u32 ndx;
	bool can;
};

/* Structure to hold all of our device specific stuff */
struct mcba_priv {
	struct can_priv can; /* must be the first member */
	struct sk_buff *echo_skb[MCBA_MAX_TX_URBS];
	struct mcba_usb_ctx tx_context[MCBA_MAX_TX_URBS];
	struct usb_device *udev;
	struct net_device *netdev;
	struct usb_anchor tx_submitted;
	struct usb_anchor rx_submitted;
	struct can_berr_counter bec;
	bool usb_ka_first_pass;
	bool can_ka_first_pass;
	bool can_speed_check;
	atomic_t free_ctx_cnt;
	void *rxbuf[MCBA_MAX_RX_URBS];
	dma_addr_t rxbuf_dma[MCBA_MAX_RX_URBS];
	int rx_pipe;
	int tx_pipe;
};

/* CAN frame */
struct __packed mcba_usb_msg_can {
	u8 cmd_id;
	__be16 eid;
	__be16 sid;
	u8 dlc;
	u8 data[8];
	u8 timestamp[4];
	u8 checksum;
};

/* command frame */
struct __packed mcba_usb_msg {
	u8 cmd_id;
	u8 unused[18];
};

struct __packed mcba_usb_msg_ka_usb {
	u8 cmd_id;
	u8 termination_state;
	u8 soft_ver_major;
	u8 soft_ver_minor;
	u8 unused[15];
};

struct __packed mcba_usb_msg_ka_can {
	u8 cmd_id;
	u8 tx_err_cnt;
	u8 rx_err_cnt;
	u8 rx_buff_ovfl;
	u8 tx_bus_off;
	__be16 can_bitrate;
	__le16 rx_lost;
	u8 can_stat;
	u8 soft_ver_major;
	u8 soft_ver_minor;
	u8 debug_mode;
	u8 test_complete;
	u8 test_result;
	u8 unused[4];
};

struct __packed mcba_usb_msg_change_bitrate {
	u8 cmd_id;
	__be16 bitrate;
	u8 unused[16];
};

struct __packed mcba_usb_msg_termination {
	u8 cmd_id;
	u8 termination;
	u8 unused[17];
};

struct __packed mcba_usb_msg_fw_ver {
	u8 cmd_id;
	u8 pic;
	u8 unused[17];
};

static const struct usb_device_id mcba_usb_table[] = {
	{ USB_DEVICE(MCBA_VENDOR_ID, MCBA_PRODUCT_ID) },
	{} /* Terminating entry */
};

MODULE_DEVICE_TABLE(usb, mcba_usb_table);

static const u16 mcba_termination[] = { MCBA_TERMINATION_DISABLED,
					MCBA_TERMINATION_ENABLED };

static const u32 mcba_bitrate[] = { 20000,  33333,  50000,  80000,  83333,
				    100000, 125000, 150000, 175000, 200000,
				    225000, 250000, 275000, 300000, 500000,
				    625000, 800000, 1000000 };

static inline void mcba_init_ctx(struct mcba_priv *priv)
{
	int i = 0;

	for (i = 0; i < MCBA_MAX_TX_URBS; i++) {
		priv->tx_context[i].ndx = MCBA_CTX_FREE;
		priv->tx_context[i].priv = priv;
	}

	atomic_set(&priv->free_ctx_cnt, ARRAY_SIZE(priv->tx_context));
}

static inline struct mcba_usb_ctx *mcba_usb_get_free_ctx(struct mcba_priv *priv,
							 struct can_frame *cf)
{
	int i = 0;
	struct mcba_usb_ctx *ctx = NULL;

	for (i = 0; i < MCBA_MAX_TX_URBS; i++) {
		if (priv->tx_context[i].ndx == MCBA_CTX_FREE) {
			ctx = &priv->tx_context[i];
			ctx->ndx = i;

			if (cf)
				ctx->can = true;
			else
				ctx->can = false;

			atomic_dec(&priv->free_ctx_cnt);
			break;
		}
	}

	if (!atomic_read(&priv->free_ctx_cnt))
		/* That was the last free ctx. Slow down tx path */
		netif_stop_queue(priv->netdev);

	return ctx;
}

/* mcba_usb_free_ctx and mcba_usb_get_free_ctx are executed by different
 * threads. The order of execution in below function is important.
 */
static inline void mcba_usb_free_ctx(struct mcba_usb_ctx *ctx)
{
	/* Increase number of free ctxs before freeing ctx */
	atomic_inc(&ctx->priv->free_ctx_cnt);

	ctx->ndx = MCBA_CTX_FREE;

	/* Wake up the queue once ctx is marked free */
	netif_wake_queue(ctx->priv->netdev);
}

static void mcba_usb_write_bulk_callback(struct urb *urb)
{
	struct mcba_usb_ctx *ctx = urb->context;
	struct net_device *netdev;

	WARN_ON(!ctx);

	netdev = ctx->priv->netdev;

	/* free up our allocated buffer */
	usb_free_coherent(urb->dev, urb->transfer_buffer_length,
			  urb->transfer_buffer, urb->transfer_dma);

	if (ctx->can) {
		if (!netif_device_present(netdev))
			return;

		netdev->stats.tx_packets++;
		netdev->stats.tx_bytes += can_get_echo_skb(netdev, ctx->ndx,
							   NULL);
	}

	if (urb->status)
		netdev_info(netdev, "Tx URB aborted (%d)\n", urb->status);

	/* Release the context */
	mcba_usb_free_ctx(ctx);
}

/* Send data to device */
static netdev_tx_t mcba_usb_xmit(struct mcba_priv *priv,
				 struct mcba_usb_msg *usb_msg,
				 struct mcba_usb_ctx *ctx)
{
	struct urb *urb;
	u8 *buf;
	int err;

	/* create a URB, and a buffer for it, and copy the data to the URB */
	urb = usb_alloc_urb(0, GFP_ATOMIC);
	if (!urb)
		return -ENOMEM;

	buf = usb_alloc_coherent(priv->udev, MCBA_USB_TX_BUFF_SIZE, GFP_ATOMIC,
				 &urb->transfer_dma);
	if (!buf) {
		err = -ENOMEM;
		goto nomembuf;
	}

	memcpy(buf, usb_msg, MCBA_USB_TX_BUFF_SIZE);

	usb_fill_bulk_urb(urb, priv->udev, priv->tx_pipe, buf, MCBA_USB_TX_BUFF_SIZE,
			  mcba_usb_write_bulk_callback, ctx);

	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
	usb_anchor_urb(urb, &priv->tx_submitted);

	err = usb_submit_urb(urb, GFP_ATOMIC);
	if (unlikely(err))
		goto failed;

	/* Release our reference to this URB, the USB core will eventually free
	 * it entirely.
	 */
	usb_free_urb(urb);

	return 0;

failed:
	usb_unanchor_urb(urb);
	usb_free_coherent(priv->udev, MCBA_USB_TX_BUFF_SIZE, buf,
			  urb->transfer_dma);

	if (err == -ENODEV)
		netif_device_detach(priv->netdev);
	else
		netdev_warn(priv->netdev, "failed tx_urb %d\n", err);

nomembuf:
	usb_free_urb(urb);

	return err;
}

/* Send data to device */
static netdev_tx_t mcba_usb_start_xmit(struct sk_buff *skb,
				       struct net_device *netdev)
{
	struct mcba_priv *priv = netdev_priv(netdev);
	struct can_frame *cf = (struct can_frame *)skb->data;
	struct mcba_usb_ctx *ctx = NULL;
	struct net_device_stats *stats = &priv->netdev->stats;
	u16 sid;
	int err;
	struct mcba_usb_msg_can usb_msg = {
		.cmd_id = MBCA_CMD_TRANSMIT_MESSAGE_EV
	};

	if (can_dev_dropped_skb(netdev, skb))
		return NETDEV_TX_OK;

	ctx = mcba_usb_get_free_ctx(priv, cf);
	if (!ctx)
		return NETDEV_TX_BUSY;

	if (cf->can_id & CAN_EFF_FLAG) {
		/* SIDH    | SIDL                 | EIDH   | EIDL
		 * 28 - 21 | 20 19 18 x x x 17 16 | 15 - 8 | 7 - 0
		 */
		sid = MCBA_SIDL_EXID_MASK;
		/* store 28-18 bits */
		sid |= (cf->can_id & 0x1ffc0000) >> 13;
		/* store 17-16 bits */
		sid |= (cf->can_id & 0x30000) >> 16;
		put_unaligned_be16(sid, &usb_msg.sid);

		/* store 15-0 bits */
		put_unaligned_be16(cf->can_id & 0xffff, &usb_msg.eid);
	} else {
		/* SIDH   | SIDL
		 * 10 - 3 | 2 1 0 x x x x x
		 */
		put_unaligned_be16((cf->can_id & CAN_SFF_MASK) << 5,
				   &usb_msg.sid);
		usb_msg.eid = 0;
	}

	usb_msg.dlc = cf->len;

	memcpy(usb_msg.data, cf->data, usb_msg.dlc);

	if (cf->can_id & CAN_RTR_FLAG)
		usb_msg.dlc |= MCBA_DLC_RTR_MASK;

	can_put_echo_skb(skb, priv->netdev, ctx->ndx, 0);

	err = mcba_usb_xmit(priv, (struct mcba_usb_msg *)&usb_msg, ctx);
	if (err)
		goto xmit_failed;

	return NETDEV_TX_OK;

xmit_failed:
	can_free_echo_skb(priv->netdev, ctx->ndx, NULL);
	mcba_usb_free_ctx(ctx);
	stats->tx_dropped++;

	return NETDEV_TX_OK;
}

/* Send cmd to device */
static void mcba_usb_xmit_cmd(struct mcba_priv *priv,
			      struct mcba_usb_msg *usb_msg)
{
	struct mcba_usb_ctx *ctx = NULL;
	int err;

	ctx = mcba_usb_get_free_ctx(priv, NULL);
	if (!ctx) {
		netdev_err(priv->netdev,
			   "Lack of free ctx. Sending (%d) cmd aborted",
			   usb_msg->cmd_id);

		return;
	}

	err = mcba_usb_xmit(priv, usb_msg, ctx);
	if (err)
		netdev_err(priv->netdev, "Failed to send cmd (%d)",
			   usb_msg->cmd_id);
}

static void mcba_usb_xmit_change_bitrate(struct mcba_priv *priv, u16 bitrate)
{
	struct mcba_usb_msg_change_bitrate usb_msg = {
		.cmd_id = MBCA_CMD_CHANGE_BIT_RATE
	};

	put_unaligned_be16(bitrate, &usb_msg.bitrate);

	mcba_usb_xmit_cmd(priv, (struct mcba_usb_msg *)&usb_msg);
}

static void mcba_usb_xmit_read_fw_ver(struct mcba_priv *priv, u8 pic)
{
	struct mcba_usb_msg_fw_ver usb_msg = {
		.cmd_id = MBCA_CMD_READ_FW_VERSION,
		.pic = pic
	};

	mcba_usb_xmit_cmd(priv, (struct mcba_usb_msg *)&usb_msg);
}

static void mcba_usb_process_can(struct mcba_priv *priv,
				 struct mcba_usb_msg_can *msg)
{
	struct can_frame *cf;
	struct sk_buff *skb;
	struct net_device_stats *stats = &priv->netdev->stats;
	u16 sid;

	skb = alloc_can_skb(priv->netdev, &cf);
	if (!skb)
		return;

	sid = get_unaligned_be16(&msg->sid);

	if (sid & MCBA_SIDL_EXID_MASK) {
		/* SIDH    | SIDL                 | EIDH   | EIDL
		 * 28 - 21 | 20 19 18 x x x 17 16 | 15 - 8 | 7 - 0
		 */
		cf->can_id = CAN_EFF_FLAG;

		/* store 28-18 bits */
		cf->can_id |= (sid & 0xffe0) << 13;
		/* store 17-16 bits */
		cf->can_id |= (sid & 3) << 16;
		/* store 15-0 bits */
		cf->can_id |= get_unaligned_be16(&msg->eid);
	} else {
		/* SIDH   | SIDL
		 * 10 - 3 | 2 1 0 x x x x x
		 */
		cf->can_id = (sid & 0xffe0) >> 5;
	}

	cf->len = can_cc_dlc2len(msg->dlc & MCBA_DLC_MASK);

	if (msg->dlc & MCBA_DLC_RTR_MASK) {
		cf->can_id |= CAN_RTR_FLAG;
	} else {
		memcpy(cf->data, msg->data, cf->len);

		stats->rx_bytes += cf->len;
	}
	stats->rx_packets++;

	netif_rx(skb);
}

static void mcba_usb_process_ka_usb(struct mcba_priv *priv,
				    struct mcba_usb_msg_ka_usb *msg)
{
	if (unlikely(priv->usb_ka_first_pass)) {
		netdev_info(priv->netdev, "PIC USB version %u.%u\n",
			    msg->soft_ver_major, msg->soft_ver_minor);

		priv->usb_ka_first_pass = false;
	}

	if (msg->termination_state == MCBA_VER_TERMINATION_ON)
		priv->can.termination = MCBA_TERMINATION_ENABLED;
	else
		priv->can.termination = MCBA_TERMINATION_DISABLED;
}

static u32 convert_can2host_bitrate(struct mcba_usb_msg_ka_can *msg)
{
	const u32 bitrate = get_unaligned_be16(&msg->can_bitrate);

	if ((bitrate == 33) || (bitrate == 83))
		return bitrate * 1000 + 333;
	else
		return bitrate * 1000;
}

static void mcba_usb_process_ka_can(struct mcba_priv *priv,
				    struct mcba_usb_msg_ka_can *msg)
{
	if (unlikely(priv->can_ka_first_pass)) {
		netdev_info(priv->netdev, "PIC CAN version %u.%u\n",
			    msg->soft_ver_major, msg->soft_ver_minor);

		priv->can_ka_first_pass = false;
	}

	if (unlikely(priv->can_speed_check)) {
		const u32 bitrate = convert_can2host_bitrate(msg);

		priv->can_speed_check = false;

		if (bitrate != priv->can.bittiming.bitrate)
			netdev_err(
			    priv->netdev,
			    "Wrong bitrate reported by the device (%u). Expected %u",
			    bitrate, priv->can.bittiming.bitrate);
	}

	priv->bec.txerr = msg->tx_err_cnt;
	priv->bec.rxerr = msg->rx_err_cnt;

	if (msg->tx_bus_off)
		priv->can.state = CAN_STATE_BUS_OFF;

	else if ((priv->bec.txerr > MCBA_CAN_STATE_ERR_PSV_TH) ||
		 (priv->bec.rxerr > MCBA_CAN_STATE_ERR_PSV_TH))
		priv->can.state = CAN_STATE_ERROR_PASSIVE;

	else if ((priv->bec.txerr > MCBA_CAN_STATE_WRN_TH) ||
		 (priv->bec.rxerr > MCBA_CAN_STATE_WRN_TH))
		priv->can.state = CAN_STATE_ERROR_WARNING;
}

static void mcba_usb_process_rx(struct mcba_priv *priv,
				struct mcba_usb_msg *msg)
{
	switch (msg->cmd_id) {
	case MBCA_CMD_I_AM_ALIVE_FROM_CAN:
		mcba_usb_process_ka_can(priv,
					(struct mcba_usb_msg_ka_can *)msg);
		break;

	case MBCA_CMD_I_AM_ALIVE_FROM_USB:
		mcba_usb_process_ka_usb(priv,
					(struct mcba_usb_msg_ka_usb *)msg);
		break;

	case MBCA_CMD_RECEIVE_MESSAGE:
		mcba_usb_process_can(priv, (struct mcba_usb_msg_can *)msg);
		break;

	case MBCA_CMD_NOTHING_TO_SEND:
		/* Side effect of communication between PIC_USB and PIC_CAN.
		 * PIC_CAN is telling us that it has nothing to send
		 */
		break;

	case MBCA_CMD_TRANSMIT_MESSAGE_RSP:
		/* Transmission response from the device containing timestamp */
		break;

	default:
		netdev_warn(priv->netdev, "Unsupported msg (0x%X)",
			    msg->cmd_id);
		break;
	}
}

/* Callback for reading data from device
 *
 * Check urb status, call read function and resubmit urb read operation.
 */
static void mcba_usb_read_bulk_callback(struct urb *urb)
{
	struct mcba_priv *priv = urb->context;
	struct net_device *netdev;
	int retval;
	int pos = 0;

	netdev = priv->netdev;

	if (!netif_device_present(netdev))
		return;

	switch (urb->status) {
	case 0: /* success */
		break;

	case -ENOENT:
	case -EPIPE:
	case -EPROTO:
	case -ESHUTDOWN:
		return;

	default:
		netdev_info(netdev, "Rx URB aborted (%d)\n", urb->status);

		goto resubmit_urb;
	}

	while (pos < urb->actual_length) {
		struct mcba_usb_msg *msg;

		if (pos + sizeof(struct mcba_usb_msg) > urb->actual_length) {
			netdev_err(priv->netdev, "format error\n");
			break;
		}

		msg = (struct mcba_usb_msg *)(urb->transfer_buffer + pos);
		mcba_usb_process_rx(priv, msg);

		pos += sizeof(struct mcba_usb_msg);
	}

resubmit_urb:

	usb_fill_bulk_urb(urb, priv->udev,
			  priv->rx_pipe,
			  urb->transfer_buffer, MCBA_USB_RX_BUFF_SIZE,
			  mcba_usb_read_bulk_callback, priv);

	retval = usb_submit_urb(urb, GFP_ATOMIC);

	if (retval == -ENODEV)
		netif_device_detach(netdev);
	else if (retval)
		netdev_err(netdev, "failed resubmitting read bulk urb: %d\n",
			   retval);
}

/* Start USB device */
static int mcba_usb_start(struct mcba_priv *priv)
{
	struct net_device *netdev = priv->netdev;
	int err, i;

	mcba_init_ctx(priv);

	for (i = 0; i < MCBA_MAX_RX_URBS; i++) {
		struct urb *urb = NULL;
		u8 *buf;
		dma_addr_t buf_dma;

		/* create a URB, and a buffer for it */
		urb = usb_alloc_urb(0, GFP_KERNEL);
		if (!urb) {
			err = -ENOMEM;
			break;
		}

		buf = usb_alloc_coherent(priv->udev, MCBA_USB_RX_BUFF_SIZE,
					 GFP_KERNEL, &buf_dma);
		if (!buf) {
			netdev_err(netdev, "No memory left for USB buffer\n");
			usb_free_urb(urb);
			err = -ENOMEM;
			break;
		}

		urb->transfer_dma = buf_dma;

		usb_fill_bulk_urb(urb, priv->udev,
				  priv->rx_pipe,
				  buf, MCBA_USB_RX_BUFF_SIZE,
				  mcba_usb_read_bulk_callback, priv);
		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
		usb_anchor_urb(urb, &priv->rx_submitted);

		err = usb_submit_urb(urb, GFP_KERNEL);
		if (err) {
			usb_unanchor_urb(urb);
			usb_free_coherent(priv->udev, MCBA_USB_RX_BUFF_SIZE,
					  buf, buf_dma);
			usb_free_urb(urb);
			break;
		}

		priv->rxbuf[i] = buf;
		priv->rxbuf_dma[i] = buf_dma;

		/* Drop reference, USB core will take care of freeing it */
		usb_free_urb(urb);
	}

	/* Did we submit any URBs */
	if (i == 0) {
		netdev_warn(netdev, "couldn't setup read URBs\n");
		return err;
	}

	/* Warn if we've couldn't transmit all the URBs */
	if (i < MCBA_MAX_RX_URBS)
		netdev_warn(netdev, "rx performance may be slow\n");

	mcba_usb_xmit_read_fw_ver(priv, MCBA_VER_REQ_USB);
	mcba_usb_xmit_read_fw_ver(priv, MCBA_VER_REQ_CAN);

	return err;
}

/* Open USB device */
static int mcba_usb_open(struct net_device *netdev)
{
	struct mcba_priv *priv = netdev_priv(netdev);
	int err;

	/* common open */
	err = open_candev(netdev);
	if (err)
		return err;

	priv->can_speed_check = true;
	priv->can.state = CAN_STATE_ERROR_ACTIVE;

	netif_start_queue(netdev);

	return 0;
}

static void mcba_urb_unlink(struct mcba_priv *priv)
{
	int i;

	usb_kill_anchored_urbs(&priv->rx_submitted);

	for (i = 0; i < MCBA_MAX_RX_URBS; ++i)
		usb_free_coherent(priv->udev, MCBA_USB_RX_BUFF_SIZE,
				  priv->rxbuf[i], priv->rxbuf_dma[i]);

	usb_kill_anchored_urbs(&priv->tx_submitted);
}

/* Close USB device */
static int mcba_usb_close(struct net_device *netdev)
{
	struct mcba_priv *priv = netdev_priv(netdev);

	priv->can.state = CAN_STATE_STOPPED;

	netif_stop_queue(netdev);

	/* Stop polling */
	mcba_urb_unlink(priv);

	close_candev(netdev);

	return 0;
}

/* Set network device mode
 *
 * Maybe we should leave this function empty, because the device
 * set mode variable with open command.
 */
static int mcba_net_set_mode(struct net_device *netdev, enum can_mode mode)
{
	return 0;
}

static int mcba_net_get_berr_counter(const struct net_device *netdev,
				     struct can_berr_counter *bec)
{
	struct mcba_priv *priv = netdev_priv(netdev);

	bec->txerr = priv->bec.txerr;
	bec->rxerr = priv->bec.rxerr;

	return 0;
}

static const struct net_device_ops mcba_netdev_ops = {
	.ndo_open = mcba_usb_open,
	.ndo_stop = mcba_usb_close,
	.ndo_start_xmit = mcba_usb_start_xmit,
};

static const struct ethtool_ops mcba_ethtool_ops = {
	.get_ts_info = ethtool_op_get_ts_info,
};

/* Microchip CANBUS has hardcoded bittiming values by default.
 * This function sends request via USB to change the speed and align bittiming
 * values for presentation purposes only
 */
static int mcba_net_set_bittiming(struct net_device *netdev)
{
	struct mcba_priv *priv = netdev_priv(netdev);
	const u16 bitrate_kbps = priv->can.bittiming.bitrate / 1000;

	mcba_usb_xmit_change_bitrate(priv, bitrate_kbps);

	return 0;
}

static int mcba_set_termination(struct net_device *netdev, u16 term)
{
	struct mcba_priv *priv = netdev_priv(netdev);
	struct mcba_usb_msg_termination usb_msg = {
		.cmd_id = MBCA_CMD_SETUP_TERMINATION_RESISTANCE
	};

	if (term == MCBA_TERMINATION_ENABLED)
		usb_msg.termination = MCBA_VER_TERMINATION_ON;
	else
		usb_msg.termination = MCBA_VER_TERMINATION_OFF;

	mcba_usb_xmit_cmd(priv, (struct mcba_usb_msg *)&usb_msg);

	return 0;
}

static int mcba_usb_probe(struct usb_interface *intf,
			  const struct usb_device_id *id)
{
	struct net_device *netdev;
	struct mcba_priv *priv;
	int err;
	struct usb_device *usbdev = interface_to_usbdev(intf);
	struct usb_endpoint_descriptor *in, *out;

	err = usb_find_common_endpoints(intf->cur_altsetting, &in, &out, NULL, NULL);
	if (err) {
		dev_err(&intf->dev, "Can't find endpoints\n");
		return err;
	}

	netdev = alloc_candev(sizeof(struct mcba_priv), MCBA_MAX_TX_URBS);
	if (!netdev) {
		dev_err(&intf->dev, "Couldn't alloc candev\n");
		return -ENOMEM;
	}

	priv = netdev_priv(netdev);

	priv->udev = usbdev;
	priv->netdev = netdev;
	priv->usb_ka_first_pass = true;
	priv->can_ka_first_pass = true;
	priv->can_speed_check = false;

	init_usb_anchor(&priv->rx_submitted);
	init_usb_anchor(&priv->tx_submitted);

	usb_set_intfdata(intf, priv);

	/* Init CAN device */
	priv->can.state = CAN_STATE_STOPPED;
	priv->can.termination_const = mcba_termination;
	priv->can.termination_const_cnt = ARRAY_SIZE(mcba_termination);
	priv->can.bitrate_const = mcba_bitrate;
	priv->can.bitrate_const_cnt = ARRAY_SIZE(mcba_bitrate);

	priv->can.do_set_termination = mcba_set_termination;
	priv->can.do_set_mode = mcba_net_set_mode;
	priv->can.do_get_berr_counter = mcba_net_get_berr_counter;
	priv->can.do_set_bittiming = mcba_net_set_bittiming;

	netdev->netdev_ops = &mcba_netdev_ops;
	netdev->ethtool_ops = &mcba_ethtool_ops;

	netdev->flags |= IFF_ECHO; /* we support local echo */

	SET_NETDEV_DEV(netdev, &intf->dev);

	err = register_candev(netdev);
	if (err) {
		netdev_err(netdev, "couldn't register CAN device: %d\n", err);

		goto cleanup_free_candev;
	}

	priv->rx_pipe = usb_rcvbulkpipe(priv->udev, in->bEndpointAddress);
	priv->tx_pipe = usb_sndbulkpipe(priv->udev, out->bEndpointAddress);

	/* Start USB dev only if we have successfully registered CAN device */
	err = mcba_usb_start(priv);
	if (err) {
		if (err == -ENODEV)
			netif_device_detach(priv->netdev);

		netdev_warn(netdev, "couldn't start device: %d\n", err);

		goto cleanup_unregister_candev;
	}

	dev_info(&intf->dev, "Microchip CAN BUS Analyzer connected\n");

	return 0;

cleanup_unregister_candev:
	unregister_candev(priv->netdev);

cleanup_free_candev:
	free_candev(netdev);

	return err;
}

/* Called by the usb core when driver is unloaded or device is removed */
static void mcba_usb_disconnect(struct usb_interface *intf)
{
	struct mcba_priv *priv = usb_get_intfdata(intf);

	usb_set_intfdata(intf, NULL);

	netdev_info(priv->netdev, "device disconnected\n");

	unregister_candev(priv->netdev);
	mcba_urb_unlink(priv);
	free_candev(priv->netdev);
}

static struct usb_driver mcba_usb_driver = {
	.name = MCBA_MODULE_NAME,
	.probe = mcba_usb_probe,
	.disconnect = mcba_usb_disconnect,
	.id_table = mcba_usb_table,
};

module_usb_driver(mcba_usb_driver);

MODULE_AUTHOR("Remigiusz Kołłątaj <remigiusz.kollataj@mobica.com>");
MODULE_DESCRIPTION("SocketCAN driver for Microchip CAN BUS Analyzer Tool");
MODULE_LICENSE("GPL v2");