[PATCH v6 1/2] usb: serial: add support for CH348

[Corentin Labbe]

The CH348 is an USB octo port serial adapter.
The device multiplexes all 8 ports in the same pair of Bulk endpoints.
Since there is no public datasheet, unfortunately it remains some magic values

Signed-off-by: Corentin Labbe <clabbe@xxxxxxxxxxxx>
---
 drivers/usb/serial/Kconfig  |   9 +
 drivers/usb/serial/Makefile |   1 +
 drivers/usb/serial/ch348.c  | 491 ++++++++++++++++++++++++++++++++++++
 3 files changed, 501 insertions(+)
 create mode 100644 drivers/usb/serial/ch348.c

diff --git a/drivers/usb/serial/Kconfig b/drivers/usb/serial/Kconfig
index ef8d1c73c754..1e1842656b54 100644
--- a/drivers/usb/serial/Kconfig
+++ b/drivers/usb/serial/Kconfig
@@ -112,6 +112,15 @@ config USB_SERIAL_CH341
 	  To compile this driver as a module, choose M here: the
 	  module will be called ch341.
 
+config USB_SERIAL_CH348
+	tristate "USB Winchiphead CH348 Octo Port Serial Driver"
+	help
+	  Say Y here if you want to use a Winchiphead CH348 octo port
+	  USB to serial adapter.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ch348.
+
 config USB_SERIAL_WHITEHEAT
 	tristate "USB ConnectTech WhiteHEAT Serial Driver"
 	select USB_EZUSB_FX2
diff --git a/drivers/usb/serial/Makefile b/drivers/usb/serial/Makefile
index c7bb1a88173e..d16ff59fde68 100644
--- a/drivers/usb/serial/Makefile
+++ b/drivers/usb/serial/Makefile
@@ -15,6 +15,7 @@ obj-$(CONFIG_USB_SERIAL_AIRCABLE)		+= aircable.o
 obj-$(CONFIG_USB_SERIAL_ARK3116)		+= ark3116.o
 obj-$(CONFIG_USB_SERIAL_BELKIN)			+= belkin_sa.o
 obj-$(CONFIG_USB_SERIAL_CH341)			+= ch341.o
+obj-$(CONFIG_USB_SERIAL_CH348)			+= ch348.o
 obj-$(CONFIG_USB_SERIAL_CP210X)			+= cp210x.o
 obj-$(CONFIG_USB_SERIAL_CYBERJACK)		+= cyberjack.o
 obj-$(CONFIG_USB_SERIAL_CYPRESS_M8)		+= cypress_m8.o
diff --git a/drivers/usb/serial/ch348.c b/drivers/usb/serial/ch348.c
new file mode 100644
index 000000000000..f89ef554954f
--- /dev/null
+++ b/drivers/usb/serial/ch348.c
@@ -0,0 +1,491 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB serial driver for USB to Octal UARTs chip ch348.
+ *
+ * Copyright (C) 2022 Corentin Labbe <clabbe@xxxxxxxxxxxx>
+ * With the help of Neil Armstrong <neil.armstrong@xxxxxxxxxx>
+ */
+
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/serial.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define DEFAULT_BAUD_RATE 9600
+#define CH348_CMD_TIMEOUT   2000
+
+#define CH348_CTO_D	0x01
+#define CH348_CTO_R	0x02
+
+#define CH348_CTI_C	0x10
+#define CH348_CTI_DSR	0x20
+#define CH348_CTI_R	0x40
+#define CH348_CTI_DCD	0x80
+
+#define CH348_LO	0x02
+#define CH348_LP	0x04
+#define CH348_LF	0x08
+#define CH348_LB	0x10
+
+#define CMD_W_R		0xC0
+#define CMD_W_BR	0x80
+
+#define CMD_WB_E	0x90
+#define CMD_RB_E	0xC0
+
+#define M_NOR		0x00
+#define M_HF		0x03
+
+#define R_MOD		0x97
+#define R_IO_D		0x98
+#define R_IO_O		0x99
+#define R_IO_I		0x9b
+#define R_TM_O		0x9c
+#define R_INIT		0xa1
+
+#define R_C1		0x01
+#define R_C2		0x02
+#define R_C4		0x04
+#define R_C5		0x06
+
+#define R_II_B1		0x06
+#define R_II_B2		0x02
+#define R_II_B3		0x00
+
+#define CH348_RX_PORT_CHUNK_LENGTH	32
+#define CH348_RX_PORT_MAX_LENGTH	30
+
+struct ch348_rxbuf {
+	u8 port;
+	u8 length;
+	u8 data[CH348_RX_PORT_MAX_LENGTH];
+} __packed;
+
+struct ch348_txbuf {
+	u8 port;
+	__le16 length;
+	u8 data[];
+} __packed;
+
+#define CH348_TX_HDRSIZE offsetof(struct ch348_txbuf, data)
+
+struct ch348_initbuf {
+	u8 cmd;
+	u8 reg;
+	u8 port;
+	__be32 baudrate;
+	u8 format;
+	u8 paritytype;
+	u8 databits;
+	u8 rate;
+	u8 unknown;
+} __packed;
+
+#define CH348_MAXPORT 8
+
+/*
+ * The CH348 multiplexes rx & tx into a pair of Bulk USB endpoints for
+ * the 8 serial ports, and another pair of Bulk USB endpoints to
+ * set port settings and receive port status events.
+ *
+ * The USB serial cores ties every Bulk endpoints pairs to each ports,
+ * but in our case it will set port 0 with the rx/tx endpoints
+ * and port 1 with the setup/status endpoints.
+ *
+ * To still take advantage of the generic code, we (re-)initialize
+ * the USB serial port structure with the correct USB endpoint
+ * for read and write, and write proper process_read_urb()
+ * and prepare_write_buffer() to correctly (de-)multiplex data.
+ */
+
+/*
+ * struct ch348_port - per-port information
+ * @uartmode:		UART port current mode
+ */
+struct ch348_port {
+	u8 uartmode;
+};
+
+/*
+ * struct ch348 - main container for all this driver information
+ * @udev:		pointer to the CH348 USB device
+ * @ports:		List of per-port information
+ * @serial:		pointer to the serial structure
+ * @status_ep:		endpoint number for status operations
+ * @cmd_ep:		endpoint number for configure operations
+ * @status_urb:		URB for status
+ * @status_buffer:	buffer used by status_urb
+ */
+struct ch348 {
+	struct usb_device *udev;
+	struct ch348_port ports[CH348_MAXPORT];
+	struct usb_serial *serial;
+
+	int status_ep;
+	int cmd_ep;
+
+	struct urb *status_urb;
+	u8 *status_buffer;
+};
+
+struct ch348_magic {
+	u8 action;
+	u8 reg;
+	u8 control;
+} __packed;
+
+/*
+ * Some values came from vendor tree, and we have no meaning for them, this
+ * function simply use them.
+ */
+static int ch348_do_magic(struct ch348 *ch348, int portnum, u8 action, u8 reg, u8 control)
+{
+	struct ch348_magic *buffer;
+	int ret, len;
+
+	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
+	if (portnum < 4)
+		reg += 0x10 * portnum;
+	else
+		reg += 0x10 * (portnum - 4) + 0x08;
+
+	buffer->action = action;
+	buffer->reg = reg;
+	buffer->control = control;
+
+	ret = usb_bulk_msg(ch348->udev, ch348->cmd_ep, buffer, 3, &len,
+			   CH348_CMD_TIMEOUT);
+	if (ret)
+		dev_err(&ch348->udev->dev, "Failed to write magic err=%d\n", ret);
+
+	kfree(buffer);
+
+	return ret;
+}
+
+static int ch348_configure(struct ch348 *ch348, int portnum)
+{
+	int ret;
+
+	ret = ch348_do_magic(ch348, portnum, CMD_W_R, R_C2, 0x87);
+	if (ret)
+		return ret;
+
+	return ch348_do_magic(ch348, portnum, CMD_W_R, R_C4, 0x08);
+}
+
+static void ch348_process_read_urb(struct urb *urb)
+{
+	struct usb_serial_port *port = urb->context;
+	struct ch348 *ch348 = usb_get_serial_data(port->serial);
+	unsigned int portnum, usblen;
+	struct ch348_rxbuf *rxb;
+	u8 *buffer, *end;
+
+	buffer = urb->transfer_buffer;
+
+	if (urb->actual_length < 2) {
+		dev_dbg(&port->dev, "Empty rx buffer\n");
+		return;
+	}
+
+	end = buffer + urb->actual_length;
+
+	for (; buffer < end; buffer += CH348_RX_PORT_CHUNK_LENGTH) {
+		rxb = (struct ch348_rxbuf *)buffer;
+		portnum = rxb->port;
+		if (portnum >= CH348_MAXPORT) {
+			dev_dbg(&port->dev, "Invalid port %d\n", portnum);
+			break;
+		}
+
+		port = ch348->serial->port[portnum];
+
+		usblen = rxb->length;
+		if (usblen > CH348_RX_PORT_MAX_LENGTH) {
+			dev_dbg(&port->dev, "Invalid length %d for port %d\n",
+				usblen, portnum);
+			break;
+		}
+
+		tty_insert_flip_string(&port->port, rxb->data, usblen);
+		tty_flip_buffer_push(&port->port);
+		port->icount.rx += usblen;
+		usb_serial_debug_data(&port->dev, __func__, usblen, rxb->data);
+	}
+}
+
+static int ch348_prepare_write_buffer(struct usb_serial_port *port, void *dest, size_t size)
+{
+	struct ch348_txbuf *rxt = dest;
+	int count;
+
+	count = kfifo_out_locked(&port->write_fifo, rxt->data,
+				 size - CH348_TX_HDRSIZE, &port->lock);
+
+	rxt->port = port->port_number;
+	rxt->length = cpu_to_le16(count);
+
+	return count + CH348_TX_HDRSIZE;
+}
+
+static int ch348_set_uartmode(struct ch348 *ch348, int portnum, u8 index, u8 mode)
+{
+	int ret;
+
+	if (ch348->ports[portnum].uartmode == M_NOR && mode == M_HF) {
+		ret = ch348_do_magic(ch348, portnum, CMD_W_BR, R_C4, 0x51);
+		if (ret)
+			return ret;
+		ch348->ports[portnum].uartmode = M_HF;
+	}
+
+	if (ch348->ports[portnum].uartmode == M_HF && mode == M_NOR) {
+		ret = ch348_do_magic(ch348, portnum, CMD_W_BR, R_C4, 0x50);
+		if (ret)
+			return ret;
+		ch348->ports[portnum].uartmode = M_NOR;
+	}
+	return 0;
+}
+
+static void ch348_set_termios(struct tty_struct *tty, struct usb_serial_port *port,
+			      const struct ktermios *termios_old)
+{
+	struct ch348 *ch348 = usb_get_serial_data(port->serial);
+	int portnum = port->port_number;
+	struct ktermios *termios = &tty->termios;
+	int ret, sent;
+	speed_t	baudrate;
+	u8 format;
+	struct ch348_initbuf *buffer;
+
+	if (termios_old && !tty_termios_hw_change(&tty->termios, termios_old))
+		return;
+
+	buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
+	if (!buffer) {
+		if (termios_old)
+			tty->termios = *termios_old;
+		return;
+	}
+
+	baudrate = tty_get_baud_rate(tty);
+	/* test show no success on low baud and datasheet said it is not supported */
+	if (baudrate < 1200)
+		baudrate = DEFAULT_BAUD_RATE;
+	/* datasheet said it is not supported */
+	if (baudrate > 6000000)
+		baudrate = 6000000;
+
+	format = termios->c_cflag & CSTOPB ? 2 : 1;
+
+	buffer->paritytype = 0;
+	if (termios->c_cflag & PARENB) {
+		if (termios->c_cflag & PARODD)
+			buffer->paritytype += 1;
+		else
+			buffer->paritytype += 2;
+		if  (termios->c_cflag & CMSPAR)
+			buffer->paritytype += 2;
+	}
+
+	switch (C_CSIZE(tty)) {
+	case CS5:
+		buffer->databits = 5;
+		break;
+	case CS6:
+		buffer->databits = 6;
+		break;
+	case CS7:
+		buffer->databits = 7;
+		break;
+	case CS8:
+	default:
+		buffer->databits = 8;
+		break;
+	}
+	buffer->cmd = CMD_WB_E | (portnum & 0x0F);
+	buffer->reg = R_INIT;
+	buffer->port = portnum;
+	buffer->baudrate = cpu_to_be32(baudrate);
+
+	if (format == 2)
+		buffer->format = 0x02;
+	else if (format == 1)
+		buffer->format = 0x00;
+
+	buffer->rate = max_t(speed_t, 5, DIV_ROUND_CLOSEST(10000 * 15, baudrate));
+
+	ret = usb_bulk_msg(ch348->udev, ch348->cmd_ep, buffer,
+			   sizeof(*buffer), &sent, CH348_CMD_TIMEOUT);
+	if (ret < 0) {
+		dev_err(&ch348->udev->dev, "Failed to change line settings: err=%d\n",
+			ret);
+		goto out;
+	}
+
+	ret = ch348_do_magic(ch348, portnum, CMD_W_R, R_C1, 0x0F);
+	if (ret < 0)
+		goto out;
+
+	if (C_CRTSCTS(tty))
+		ret = ch348_set_uartmode(ch348, portnum, portnum, M_HF);
+	else
+		ret = ch348_set_uartmode(ch348, portnum, portnum, M_NOR);
+
+out:
+	kfree(buffer);
+}
+
+static int ch348_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	struct ch348 *ch348 = usb_get_serial_data(port->serial);
+	int ret;
+
+	if (tty)
+		ch348_set_termios(tty, port, NULL);
+
+	ret = ch348_configure(ch348, port->port_number);
+	if (ret) {
+		dev_err(&ch348->udev->dev, "Fail to configure err=%d\n", ret);
+		return ret;
+	}
+
+	return usb_serial_generic_open(tty, port);
+}
+
+static void ch348_disconnect(struct usb_serial *serial)
+{
+	struct ch348 *ch348 = usb_get_serial_data(serial);
+
+	usb_kill_urb(ch348->status_urb);
+}
+
+static int ch348_attach(struct usb_serial *serial)
+{
+	struct usb_serial_port *port0 = serial->port[1];
+	struct usb_device *usb_dev = serial->dev;
+	struct usb_endpoint_descriptor *epcmd;
+	struct usb_interface *intf;
+	struct ch348 *ch348;
+	int ret;
+
+	ch348 = kzalloc(sizeof(*ch348), GFP_KERNEL);
+	if (!ch348)
+		return -ENOMEM;
+
+	usb_set_serial_data(serial, ch348);
+
+	ch348->udev = serial->dev;
+	ch348->serial = serial;
+
+	intf = usb_ifnum_to_if(usb_dev, 0);
+	epcmd = &intf->cur_altsetting->endpoint[3].desc;
+	ret = usb_serial_generic_submit_read_urbs(port0, GFP_KERNEL);
+	if (ret)
+		return ret;
+
+	ch348->cmd_ep = usb_sndbulkpipe(usb_dev, epcmd->bEndpointAddress);
+
+	return 0;
+}
+
+static void ch348_release(struct usb_serial *serial)
+{
+	struct ch348 *ch348 = usb_get_serial_data(serial);
+	struct usb_serial_port *port0 = serial->port[1];
+
+	usb_serial_generic_close(port0);
+
+	kfree(ch348);
+}
+
+static int ch348_probe(struct usb_serial *serial, const struct usb_device_id *id)
+{
+	struct usb_device *usb_dev = serial->dev;
+	struct usb_endpoint_descriptor *epcmd;
+	struct usb_endpoint_descriptor *epread;
+	struct usb_endpoint_descriptor *epwrite;
+	struct usb_interface *intf;
+	int ret;
+
+	intf = usb_ifnum_to_if(usb_dev, 0);
+
+	ret = usb_find_common_endpoints(intf->cur_altsetting, &epread, &epwrite,
+					NULL, NULL);
+	if (ret) {
+		dev_err(&serial->dev->dev, "Failed to find basic endpoints ret=%d\n", ret);
+		return ret;
+	}
+	epcmd = &intf->cur_altsetting->endpoint[3].desc;
+
+	if (!usb_endpoint_is_bulk_out(epcmd)) {
+		dev_err(&serial->dev->dev, "Missing second bulk out\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int ch348_calc_num_ports(struct usb_serial *serial,
+				struct usb_serial_endpoints *epds)
+{
+	int i;
+
+	for (i = 1; i < CH348_MAXPORT; ++i) {
+		epds->bulk_out[i] = epds->bulk_out[0];
+		epds->bulk_in[i] = epds->bulk_in[0];
+	}
+	epds->num_bulk_out = CH348_MAXPORT;
+	epds->num_bulk_in = CH348_MAXPORT;
+
+	return CH348_MAXPORT;
+}
+
+static const struct usb_device_id ch348_ids[] = {
+	{ USB_DEVICE(0x1a86, 0x55d9), },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(usb, ch348_ids);
+
+static struct usb_serial_driver ch348_device = {
+	.driver = {
+		.owner = THIS_MODULE,
+		.name = "ch348",
+	},
+	.id_table =		ch348_ids,
+	.num_ports =		CH348_MAXPORT,
+	.num_bulk_in =		1,
+	.num_bulk_out =		2,
+	.open =			ch348_open,
+	.set_termios =		ch348_set_termios,
+	.process_read_urb =	ch348_process_read_urb,
+	.prepare_write_buffer =	ch348_prepare_write_buffer,
+	.probe =		ch348_probe,
+	.calc_num_ports =	ch348_calc_num_ports,
+	.attach =		ch348_attach,
+	.release =		ch348_release,
+	.disconnect =		ch348_disconnect,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&ch348_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, ch348_ids);
+
+MODULE_AUTHOR("Corentin Labbe <clabbe@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("USB CH348 Octo port serial converter driver");
+MODULE_LICENSE("GPL");
-- 
2.39.3