diff mbox series

[v6] USB: serial: cp210x: Add support for GPIOs on CP2108

Message ID 20210405061823.3855-1-photranvan0712@gmail.com (mailing list archive)
State Superseded
Headers show
Series [v6] USB: serial: cp210x: Add support for GPIOs on CP2108 | expand

Commit Message

Pho Tran April 5, 2021, 6:18 a.m. UTC 
From: Pho Tran <pho.tran@silabs.com>

Similar to other CP210x devices, GPIO interfaces (gpiochip) should be
supported for CP2108.

CP2108 has 4 serial interfaces but only 1 set of GPIO pins are shared
to all of those interfaces. So, just need to initialize GPIOs of CP2108
with only one interface (I use interface 0). It means just only 1 gpiochip
device file will be created for CP2108.

CP2108 has 16 GPIOs, So data types of several variables need to be is u16
instead of u8(in struct cp210x_serial_private). This doesn't affect other
CP210x devices.

Because CP2108 has 16 GPIO pins, the parameter passed by cp210x functions
will be different from other CP210x devices. So need to check part number
of the device to use correct data format  before sending commands to
devices.

Like CP2104, CP2108 have GPIO pins with configurable options. Therefore,
should be mask all pins which are not in GPIO mode in cp2108_gpio_init()
function. Alternate functions of GPIO0 to GPIO3 is determine by
enhancedfxn_IFC[0] and similar for enhancedfxn_IFC[1] and
enhancedfxn_IFC[2]. Refer to CP2108 datasheet at sector
"9: GPIO and UART pins" for more detail:
https://www.silabs.com/documents/public/data-sheets/cp2108-datasheet.pdf

Signed-off-by: Pho Tran <pho.tran@silabs.com>
---

03/15/2021: Patch v5 Modifed code according to comment of Johan:
	1. Unified the handling of CP2108 and other types and
	take care about endianness.
	2. Used suitable types data for variable.
	3. Fixed cp2108_gpio_init and add more detail on
	commit message and comment.
	4. Dropped some of the ones that don't add any value.
03/12/2021: Patch v4 used git send-mail instead of send patch by manual
follow the instructions of Johan Hovold <johan@kernel.org>.
03/05/2021: Patch v3 modified format and contents of changelog follow feedback
from Johan Hovold <johan@kernel.org>.
03/04/2021: Patch v2 modified format patch as comment from
Johan Hovold <johan@kernel.org>:
	1. Break commit message lines at 80 cols
	2. Use kernel u8 and u16 instead of the c99 ones.
03/01/2021: Initialed submission of patch "Make the CP210x driver work with
GPIOs of CP2108.".

 drivers/usb/serial/cp210x.c | 253 +++++++++++++++++++++++++++++++-----
 1 file changed, 219 insertions(+), 34 deletions(-)

Comments

kernel test robot April 5, 2021, 9:23 a.m. UTC | #1 
Hi Pho,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on usb-serial/usb-next]
[also build test WARNING on usb/usb-testing tty/tty-testing v5.12-rc6 next-20210401]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Pho-Tran/USB-serial-cp210x-Add-support-for-GPIOs-on-CP2108/20210405-141927
base:   https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git usb-next
config: x86_64-randconfig-s022-20210405 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.3-279-g6d5d9b42-dirty
        # https://github.com/0day-ci/linux/commit/a4658078c55d4396be894b30d3b94fd86b770f45
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Pho-Tran/USB-serial-cp210x-Add-support-for-GPIOs-on-CP2108/20210405-141927
        git checkout a4658078c55d4396be894b30d3b94fd86b770f45
        # save the attached .config to linux build tree
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


sparse warnings: (new ones prefixed by >>)
>> drivers/usb/serial/cp210x.c:1540:13: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le16 [addressable] [usertype] buf @@     got unsigned short [usertype] @@
   drivers/usb/serial/cp210x.c:1540:13: sparse:     expected restricted __le16 [addressable] [usertype] buf
   drivers/usb/serial/cp210x.c:1540:13: sparse:     got unsigned short [usertype]
>> drivers/usb/serial/cp210x.c:1542:19: sparse: sparse: restricted __le16 degrades to integer
>> drivers/usb/serial/cp210x.c:1581:24: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le16 [usertype] wIndex @@     got int @@
   drivers/usb/serial/cp210x.c:1581:24: sparse:     expected restricted __le16 [usertype] wIndex
   drivers/usb/serial/cp210x.c:1581:24: sparse:     got int
>> drivers/usb/serial/cp210x.c:1587:57: sparse: sparse: incorrect type in argument 6 (different base types) @@     expected unsigned short [usertype] index @@     got restricted __le16 [usertype] wIndex @@
   drivers/usb/serial/cp210x.c:1587:57: sparse:     expected unsigned short [usertype] index
   drivers/usb/serial/cp210x.c:1587:57: sparse:     got restricted __le16 [usertype] wIndex
>> drivers/usb/serial/cp210x.c:1676:14: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le16 [usertype] temp @@     got unsigned short [usertype] @@
   drivers/usb/serial/cp210x.c:1676:14: sparse:     expected restricted __le16 [usertype] temp
   drivers/usb/serial/cp210x.c:1676:14: sparse:     got unsigned short [usertype]
   drivers/usb/serial/cp210x.c:1677:32: sparse: sparse: restricted __le16 degrades to integer
   drivers/usb/serial/cp210x.c:1678:14: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le16 [usertype] temp @@     got unsigned short [usertype] @@
   drivers/usb/serial/cp210x.c:1678:14: sparse:     expected restricted __le16 [usertype] temp
   drivers/usb/serial/cp210x.c:1678:14: sparse:     got unsigned short [usertype]
   drivers/usb/serial/cp210x.c:1679:23: sparse: sparse: restricted __le16 degrades to integer
>> drivers/usb/serial/cp210x.c:1679:20: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted __le16 [usertype] gpio_latch @@     got unsigned long @@
   drivers/usb/serial/cp210x.c:1679:20: sparse:     expected restricted __le16 [usertype] gpio_latch
   drivers/usb/serial/cp210x.c:1679:20: sparse:     got unsigned long
   drivers/usb/serial/cp210x.c:1721:57: sparse: sparse: restricted __le16 degrades to integer

vim +1540 drivers/usb/serial/cp210x.c

  1496	
  1497	static int cp210x_gpio_get(struct gpio_chip *gc, unsigned int gpio)
  1498	{
  1499		struct usb_serial *serial = gpiochip_get_data(gc);
  1500		struct cp210x_serial_private *priv = usb_get_serial_data(serial);
  1501		u8 req_type = REQTYPE_DEVICE_TO_HOST;
  1502		int result;
  1503		__le16 buf;
  1504	
  1505		result = usb_autopm_get_interface(serial->interface);
  1506		if (result)
  1507			return result;
  1508	/*
  1509	 * This function will be read latch value of gpio and storage to buf(16bit)
  1510	 * where bit 0 is GPIO0, bit 1 is GPIO1, etc. Up to GPIOn where n is
  1511	 * total number of GPIO pins the interface supports.
  1512	 * Interfaces on CP2102N supports 7 GPIOs
  1513	 * Interfaces on CP2103 amd CP2104 supports 4 GPIOs
  1514	 * Enhanced interfaces on CP2105 support 3 GPIOs
  1515	 * Standard interfaces on CP2105 support 4 GPIOs
  1516	 * Interfaces on CP2108 supports 16 GPIOs
  1517	 */
  1518		switch (priv->partnum) {
  1519		/*
  1520		 * Request type to Read_Latch of CP2105 and Cp2108
  1521		 * is 0xc1 <REQTYPE_INTERFACE_TO_HOST>
  1522		 */
  1523		case CP210X_PARTNUM_CP2108:
  1524			req_type = REQTYPE_INTERFACE_TO_HOST;
  1525			result = cp210x_read_vendor_block(serial, req_type,
  1526							CP210X_READ_LATCH, &buf, sizeof(__le16));
  1527			break;
  1528		case CP210X_PARTNUM_CP2105:
  1529			req_type = REQTYPE_INTERFACE_TO_HOST;
  1530			result = cp210x_read_vendor_block(serial, req_type,
  1531							CP210X_READ_LATCH, &buf, sizeof(u8));
  1532			break;
  1533		default:
  1534			result = cp210x_read_vendor_block(serial, req_type,
  1535							CP210X_READ_LATCH, &buf, sizeof(u8));
  1536			break;
  1537		}
  1538		if (result < 0)
  1539			return result;
> 1540		buf = le16_to_cpu(buf);
  1541		usb_autopm_put_interface(serial->interface);
> 1542		return !!(buf & BIT(gpio));
  1543	}
  1544	
  1545	static void cp210x_gpio_set(struct gpio_chip *gc, unsigned int gpio, int value)
  1546	{
  1547		struct usb_serial *serial = gpiochip_get_data(gc);
  1548		struct cp210x_serial_private *priv = usb_get_serial_data(serial);
  1549		struct cp210x_gpio_write buf;
  1550		__le16 wIndex;
  1551		int result;
  1552	
  1553		if (value == 1) {
  1554			buf.cp210x_8gpios.state = BIT(gpio);
  1555			buf.cp210x_16gpios.state = cpu_to_le16(BIT(gpio));
  1556		} else {
  1557			buf.cp210x_8gpios.state = 0;
  1558			buf.cp210x_16gpios.state = 0;
  1559		}
  1560		buf.cp210x_8gpios.mask = BIT(gpio);
  1561		buf.cp210x_16gpios.mask = cpu_to_le16(BIT(gpio));
  1562	
  1563		result = usb_autopm_get_interface(serial->interface);
  1564		if (result)
  1565			goto out;
  1566	
  1567		switch (priv->partnum) {
  1568		case CP210X_PARTNUM_CP2108:
  1569			result = cp210x_write_vendor_block(serial,
  1570								REQTYPE_HOST_TO_INTERFACE,
  1571								CP210X_WRITE_LATCH, &buf.cp210x_16gpios,
  1572								sizeof(buf.cp210x_16gpios));
  1573			break;
  1574		case CP210X_PARTNUM_CP2105:
  1575			result = cp210x_write_vendor_block(serial,
  1576								REQTYPE_HOST_TO_INTERFACE,
  1577								CP210X_WRITE_LATCH, &buf.cp210x_8gpios,
  1578								sizeof(buf.cp210x_8gpios));
  1579			break;
  1580		default:
> 1581			wIndex = buf.cp210x_8gpios.state << 8 | buf.cp210x_8gpios.mask;
  1582			result = usb_control_msg(serial->dev,
  1583								usb_sndctrlpipe(serial->dev, 0),
  1584								CP210X_VENDOR_SPECIFIC,
  1585								REQTYPE_HOST_TO_DEVICE,
  1586								CP210X_WRITE_LATCH,
> 1587								wIndex,
  1588								NULL, 0, USB_CTRL_SET_TIMEOUT);
  1589			break;
  1590		}
  1591		usb_autopm_put_interface(serial->interface);
  1592	
  1593	out:
  1594		if (result < 0) {
  1595			dev_err(&serial->interface->dev, "failed to set GPIO value: %d\n",
  1596					result);
  1597		}
  1598	}
  1599	
  1600	static int cp210x_gpio_direction_get(struct gpio_chip *gc, unsigned int gpio)
  1601	{
  1602		struct usb_serial *serial = gpiochip_get_data(gc);
  1603		struct cp210x_serial_private *priv = usb_get_serial_data(serial);
  1604	
  1605		return priv->gpio_input & BIT(gpio);
  1606	}
  1607	
  1608	static int cp210x_gpio_direction_input(struct gpio_chip *gc, unsigned int gpio)
  1609	{
  1610		struct usb_serial *serial = gpiochip_get_data(gc);
  1611		struct cp210x_serial_private *priv = usb_get_serial_data(serial);
  1612	
  1613		if (priv->partnum == CP210X_PARTNUM_CP2105) {
  1614			/* hardware does not support an input mode */
  1615			return -ENOTSUPP;
  1616		}
  1617	
  1618		/* push-pull pins cannot be changed to be inputs */
  1619		if (priv->gpio_pushpull & BIT(gpio))
  1620			return -EINVAL;
  1621	
  1622		/* make sure to release pin if it is being driven low */
  1623		cp210x_gpio_set(gc, gpio, 1);
  1624	
  1625		priv->gpio_input |= BIT(gpio);
  1626	
  1627		return 0;
  1628	}
  1629	
  1630	static int cp210x_gpio_direction_output(struct gpio_chip *gc, unsigned int gpio,
  1631						int value)
  1632	{
  1633		struct usb_serial *serial = gpiochip_get_data(gc);
  1634		struct cp210x_serial_private *priv = usb_get_serial_data(serial);
  1635	
  1636		priv->gpio_input &= ~BIT(gpio);
  1637		cp210x_gpio_set(gc, gpio, value);
  1638	
  1639		return 0;
  1640	}
  1641	
  1642	static int cp210x_gpio_set_config(struct gpio_chip *gc, unsigned int gpio,
  1643					  unsigned long config)
  1644	{
  1645		struct usb_serial *serial = gpiochip_get_data(gc);
  1646		struct cp210x_serial_private *priv = usb_get_serial_data(serial);
  1647		enum pin_config_param param = pinconf_to_config_param(config);
  1648	
  1649		/* Succeed only if in correct mode (this can't be set at runtime) */
  1650		if ((param == PIN_CONFIG_DRIVE_PUSH_PULL) &&
  1651		    (priv->gpio_pushpull & BIT(gpio)))
  1652			return 0;
  1653	
  1654		if ((param == PIN_CONFIG_DRIVE_OPEN_DRAIN) &&
  1655		    !(priv->gpio_pushpull & BIT(gpio)))
  1656			return 0;
  1657	
  1658		return -ENOTSUPP;
  1659	}
  1660	
  1661	static int cp2108_gpio_init(struct usb_serial *serial)
  1662	{
  1663		struct cp210x_serial_private *priv = usb_get_serial_data(serial);
  1664		struct cp210x_quad_port_config config;
  1665		__le16 gpio_latch;
  1666		__le16 temp;
  1667		int result;
  1668		u8 i;
  1669	
  1670		result = cp210x_read_vendor_block(serial, REQTYPE_DEVICE_TO_HOST,
  1671						  CP210X_GET_PORTCONFIG, &config,
  1672						  sizeof(config));
  1673		if (result < 0)
  1674			return result;
  1675		priv->gc.ngpio = 16;
> 1676		temp = le16_to_cpu(config.reset_state.gpio_mode_PB1);
  1677		priv->gpio_pushpull = (temp & CP2108_GPIO_MODE_MASK) >> CP2108_GPIO_MODE_OFFSET;
  1678		temp = le16_to_cpu(config.reset_state.gpio_latch_PB1);
> 1679		gpio_latch = (temp & CP2108_GPIO_MODE_MASK) >> CP2108_GPIO_MODE_OFFSET;
  1680		/*
  1681		 * Mark all pins which are not in GPIO mode
  1682		 * Refer to table 9.1: GPIO Mode alternate Functions on CP2108 datasheet:
  1683		 * https://www.silabs.com/documents/public/data-sheets/cp2108-datasheet.pdf
  1684		 * Alternate Functions of GPIO0 to GPIO3 is determine by enhancedfxn_IFC[0]
  1685		 * and the same for other pins, enhancedfxn_IFC[1]: GPIO4 to GPIO7,
  1686		 * enhancedfxn_IFC[2]: GPIO8 to GPIO11, enhancedfxn_IFC[3]: GPIO12 to GPIO15.
  1687		 */
  1688		for (i = 0; i < 4; i++) {
  1689			switch (config.enhancedfxn_IFC[i]) {
  1690			case EF_IFC_GPIO_TXLED:
  1691				priv->gpio_altfunc |= BIT(i * 4);
  1692				break;
  1693			case EF_IFC_GPIO_RXLED:
  1694				priv->gpio_altfunc |= BIT((i * 4) + 1);
  1695				break;
  1696			case EF_IFC_GPIO_RS485_LOGIC:
  1697			case EF_IFC_GPIO_RS485:
  1698				priv->gpio_altfunc |= BIT((i * 4) + 2);
  1699				break;
  1700			case EF_IFC_GPIO_CLOCK:
  1701				priv->gpio_altfunc |= BIT((i * 4) + 3);
  1702				break;
  1703			case EF_IFC_DYNAMIC_SUSPEND:
  1704				priv->gpio_altfunc |= BIT(i * 4);
  1705				priv->gpio_altfunc |= BIT((i * 4) + 1);
  1706				priv->gpio_altfunc |= BIT((i * 4) + 2);
  1707				priv->gpio_altfunc |= BIT((i * 4) + 3);
  1708				break;
  1709			}
  1710		}
  1711		/*
  1712		 * Like CP2102N, CP2108 has also no strict input and output pin
  1713		 * modes.
  1714		 * Do the same input mode emulation as CP2102N.
  1715		 */
  1716		for (i = 0; i < priv->gc.ngpio; ++i) {
  1717			/*
  1718			 * Set direction to "input" iff pin is open-drain and reset
  1719			 * value is 1.
  1720			 */
  1721			if (!(priv->gpio_pushpull & BIT(i)) && (gpio_latch & BIT(i)))
  1722				priv->gpio_input |= BIT(i);
  1723		}
  1724	
  1725		return 0;
  1726	}
  1727	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
diff mbox series

Patch

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 7bec1e730b20..f0ecb4315056 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -245,9 +245,9 @@  struct cp210x_serial_private {
 #ifdef CONFIG_GPIOLIB
 	struct gpio_chip	gc;
 	bool			gpio_registered;
-	u8			gpio_pushpull;
-	u8			gpio_altfunc;
-	u8			gpio_input;
+	u16			gpio_pushpull;
+	u16			gpio_altfunc;
+	u16			gpio_input;
 #endif
 	u8			partnum;
 	speed_t			min_speed;
@@ -399,6 +399,18 @@  static struct usb_serial_driver * const serial_drivers[] = {
 #define CP210X_PARTNUM_CP2102N_QFN20	0x22
 #define CP210X_PARTNUM_UNKNOWN	0xFF
 
+/*
+ * CP2108 Define bit locations for EnhancedFxn_IFCx
+ * Refer to https://www.silabs.com/documents/public/application-notes/an978-cp210x-usb-to-uart-api-specification.pdf
+ * for more information.
+ */
+#define EF_IFC_GPIO_TXLED		0x01
+#define EF_IFC_GPIO_RXLED		0x02
+#define EF_IFC_GPIO_RS485		0x04
+#define EF_IFC_GPIO_RS485_LOGIC 0x08
+#define EF_IFC_GPIO_CLOCK		0x10
+#define EF_IFC_DYNAMIC_SUSPEND	0x40
+
 /* CP210X_GET_COMM_STATUS returns these 0x13 bytes */
 struct cp210x_comm_status {
 	__le32   ulErrors;
@@ -500,6 +512,45 @@  struct cp210x_single_port_config {
 	u8	device_cfg;
 } __packed;
 
+/*
+ * Quad Port Config definitions
+ * Refer to https://www.silabs.com/documents/public/application-notes/an978-cp210x-usb-to-uart-api-specification.pdf
+ * for more information.
+ * CP210X_VENDOR_SPECIFIC, CP210X_GET_PORTCONFIG call reads these 0x49 bytes
+ * on a CP2108 chip.
+ * CP2108 Quad Port State structure(used in Quad Port Config structure)
+ */
+struct cp210x_quad_port_state {
+	__le16 gpio_mode_PB0;
+	__le16 gpio_mode_PB1;
+	__le16 gpio_mode_PB2;
+	__le16 gpio_mode_PB3;
+	__le16 gpio_mode_PB4;
+
+
+	__le16 gpio_lowpower_PB0;
+	__le16 gpio_lowpower_PB1;
+	__le16 gpio_lowpower_PB2;
+	__le16 gpio_lowpower_PB3;
+	__le16 gpio_lowpower_PB4;
+
+	__le16 gpio_latch_PB0;
+	__le16 gpio_latch_PB1;
+	__le16 gpio_latch_PB2;
+	__le16 gpio_latch_PB3;
+	__le16 gpio_latch_PB4;
+};
+
+// Cp2108 Quad Port Config structure
+struct cp210x_quad_port_config {
+	struct cp210x_quad_port_state reset_state;
+	struct cp210x_quad_port_state suspend_state;
+	u8 ipdelay_IFC[4];
+	u8 enhancedfxn_IFC[4];
+	u8 enhancedfxn_device;
+	u8 extclkfreq[4];
+} __packed;
+
 /* GPIO modes */
 #define CP210X_SCI_GPIO_MODE_OFFSET	9
 #define CP210X_SCI_GPIO_MODE_MASK	GENMASK(11, 9)
@@ -510,6 +561,9 @@  struct cp210x_single_port_config {
 #define CP210X_GPIO_MODE_OFFSET		8
 #define CP210X_GPIO_MODE_MASK		GENMASK(11, 8)
 
+#define CP2108_GPIO_MODE_OFFSET		0
+#define CP2108_GPIO_MODE_MASK		GENMASK(15, 0)
+
 /* CP2105 port configuration values */
 #define CP2105_GPIO0_TXLED_MODE		BIT(0)
 #define CP2105_GPIO1_RXLED_MODE		BIT(1)
@@ -526,12 +580,31 @@  struct cp210x_single_port_config {
 #define CP210X_2NCONFIG_GPIO_RSTLATCH_IDX	587
 #define CP210X_2NCONFIG_GPIO_CONTROL_IDX	600
 
-/* CP210X_VENDOR_SPECIFIC, CP210X_WRITE_LATCH call writes these 0x2 bytes. */
-struct cp210x_gpio_write {
+/*
+ * CP210X_VENDOR_SPECIFIC, CP210X_WRITE_LATCH call writes these
+ * 0x04 bytes on CP2108.
+ */
+struct cp210x_16gpios_write {
+	__le16	mask;
+	__le16	state;
+};
+
+/*
+ * CP210X_VENDOR_SPECIFIC, CP210X_WRITE_LATCH call writes these
+ * 0x02 bytes on CP2102N, Cp2103, Cp2104 and CP2105.
+ */
+struct cp210x_8gpios_write {
 	u8	mask;
 	u8	state;
 };
 
+//Struct cp210x_gpio_write include devices have both of 8 gpios and 16 gpios.
+struct cp210x_gpio_write {
+	struct cp210x_8gpios_write cp210x_8gpios;
+	struct cp210x_16gpios_write cp210x_16gpios;
+};
+
+
 /*
  * Helper to get interface number when we only have struct usb_serial.
  */
@@ -1298,21 +1371,45 @@  static int cp210x_gpio_get(struct gpio_chip *gc, unsigned int gpio)
 	struct cp210x_serial_private *priv = usb_get_serial_data(serial);
 	u8 req_type = REQTYPE_DEVICE_TO_HOST;
 	int result;
-	u8 buf;
-
-	if (priv->partnum == CP210X_PARTNUM_CP2105)
-		req_type = REQTYPE_INTERFACE_TO_HOST;
+	__le16 buf;
 
 	result = usb_autopm_get_interface(serial->interface);
 	if (result)
 		return result;
-
-	result = cp210x_read_vendor_block(serial, req_type,
-					  CP210X_READ_LATCH, &buf, sizeof(buf));
-	usb_autopm_put_interface(serial->interface);
+/*
+ * This function will be read latch value of gpio and storage to buf(16bit)
+ * where bit 0 is GPIO0, bit 1 is GPIO1, etc. Up to GPIOn where n is
+ * total number of GPIO pins the interface supports.
+ * Interfaces on CP2102N supports 7 GPIOs
+ * Interfaces on CP2103 amd CP2104 supports 4 GPIOs
+ * Enhanced interfaces on CP2105 support 3 GPIOs
+ * Standard interfaces on CP2105 support 4 GPIOs
+ * Interfaces on CP2108 supports 16 GPIOs
+ */
+	switch (priv->partnum) {
+	/*
+	 * Request type to Read_Latch of CP2105 and Cp2108
+	 * is 0xc1 <REQTYPE_INTERFACE_TO_HOST>
+	 */
+	case CP210X_PARTNUM_CP2108:
+		req_type = REQTYPE_INTERFACE_TO_HOST;
+		result = cp210x_read_vendor_block(serial, req_type,
+						CP210X_READ_LATCH, &buf, sizeof(__le16));
+		break;
+	case CP210X_PARTNUM_CP2105:
+		req_type = REQTYPE_INTERFACE_TO_HOST;
+		result = cp210x_read_vendor_block(serial, req_type,
+						CP210X_READ_LATCH, &buf, sizeof(u8));
+		break;
+	default:
+		result = cp210x_read_vendor_block(serial, req_type,
+						CP210X_READ_LATCH, &buf, sizeof(u8));
+		break;
+	}
 	if (result < 0)
 		return result;
-
+	buf = le16_to_cpu(buf);
+	usb_autopm_put_interface(serial->interface);
 	return !!(buf & BIT(gpio));
 }
 
@@ -1321,37 +1418,49 @@  static void cp210x_gpio_set(struct gpio_chip *gc, unsigned int gpio, int value)
 	struct usb_serial *serial = gpiochip_get_data(gc);
 	struct cp210x_serial_private *priv = usb_get_serial_data(serial);
 	struct cp210x_gpio_write buf;
+	__le16 wIndex;
 	int result;
 
-	if (value == 1)
-		buf.state = BIT(gpio);
-	else
-		buf.state = 0;
-
-	buf.mask = BIT(gpio);
+	if (value == 1) {
+		buf.cp210x_8gpios.state = BIT(gpio);
+		buf.cp210x_16gpios.state = cpu_to_le16(BIT(gpio));
+	} else {
+		buf.cp210x_8gpios.state = 0;
+		buf.cp210x_16gpios.state = 0;
+	}
+	buf.cp210x_8gpios.mask = BIT(gpio);
+	buf.cp210x_16gpios.mask = cpu_to_le16(BIT(gpio));
 
 	result = usb_autopm_get_interface(serial->interface);
 	if (result)
 		goto out;
 
-	if (priv->partnum == CP210X_PARTNUM_CP2105) {
+	switch (priv->partnum) {
+	case CP210X_PARTNUM_CP2108:
 		result = cp210x_write_vendor_block(serial,
-						   REQTYPE_HOST_TO_INTERFACE,
-						   CP210X_WRITE_LATCH, &buf,
-						   sizeof(buf));
-	} else {
-		u16 wIndex = buf.state << 8 | buf.mask;
-
+							REQTYPE_HOST_TO_INTERFACE,
+							CP210X_WRITE_LATCH, &buf.cp210x_16gpios,
+							sizeof(buf.cp210x_16gpios));
+		break;
+	case CP210X_PARTNUM_CP2105:
+		result = cp210x_write_vendor_block(serial,
+							REQTYPE_HOST_TO_INTERFACE,
+							CP210X_WRITE_LATCH, &buf.cp210x_8gpios,
+							sizeof(buf.cp210x_8gpios));
+		break;
+	default:
+		wIndex = buf.cp210x_8gpios.state << 8 | buf.cp210x_8gpios.mask;
 		result = usb_control_msg(serial->dev,
-					 usb_sndctrlpipe(serial->dev, 0),
-					 CP210X_VENDOR_SPECIFIC,
-					 REQTYPE_HOST_TO_DEVICE,
-					 CP210X_WRITE_LATCH,
-					 wIndex,
-					 NULL, 0, USB_CTRL_SET_TIMEOUT);
+							usb_sndctrlpipe(serial->dev, 0),
+							CP210X_VENDOR_SPECIFIC,
+							REQTYPE_HOST_TO_DEVICE,
+							CP210X_WRITE_LATCH,
+							wIndex,
+							NULL, 0, USB_CTRL_SET_TIMEOUT);
+		break;
 	}
-
 	usb_autopm_put_interface(serial->interface);
+
 out:
 	if (result < 0) {
 		dev_err(&serial->interface->dev, "failed to set GPIO value: %d\n",
@@ -1420,6 +1529,73 @@  static int cp210x_gpio_set_config(struct gpio_chip *gc, unsigned int gpio,
 	return -ENOTSUPP;
 }
 
+static int cp2108_gpio_init(struct usb_serial *serial)
+{
+	struct cp210x_serial_private *priv = usb_get_serial_data(serial);
+	struct cp210x_quad_port_config config;
+	__le16 gpio_latch;
+	__le16 temp;
+	int result;
+	u8 i;
+
+	result = cp210x_read_vendor_block(serial, REQTYPE_DEVICE_TO_HOST,
+					  CP210X_GET_PORTCONFIG, &config,
+					  sizeof(config));
+	if (result < 0)
+		return result;
+	priv->gc.ngpio = 16;
+	temp = le16_to_cpu(config.reset_state.gpio_mode_PB1);
+	priv->gpio_pushpull = (temp & CP2108_GPIO_MODE_MASK) >> CP2108_GPIO_MODE_OFFSET;
+	temp = le16_to_cpu(config.reset_state.gpio_latch_PB1);
+	gpio_latch = (temp & CP2108_GPIO_MODE_MASK) >> CP2108_GPIO_MODE_OFFSET;
+	/*
+	 * Mark all pins which are not in GPIO mode
+	 * Refer to table 9.1: GPIO Mode alternate Functions on CP2108 datasheet:
+	 * https://www.silabs.com/documents/public/data-sheets/cp2108-datasheet.pdf
+	 * Alternate Functions of GPIO0 to GPIO3 is determine by enhancedfxn_IFC[0]
+	 * and the same for other pins, enhancedfxn_IFC[1]: GPIO4 to GPIO7,
+	 * enhancedfxn_IFC[2]: GPIO8 to GPIO11, enhancedfxn_IFC[3]: GPIO12 to GPIO15.
+	 */
+	for (i = 0; i < 4; i++) {
+		switch (config.enhancedfxn_IFC[i]) {
+		case EF_IFC_GPIO_TXLED:
+			priv->gpio_altfunc |= BIT(i * 4);
+			break;
+		case EF_IFC_GPIO_RXLED:
+			priv->gpio_altfunc |= BIT((i * 4) + 1);
+			break;
+		case EF_IFC_GPIO_RS485_LOGIC:
+		case EF_IFC_GPIO_RS485:
+			priv->gpio_altfunc |= BIT((i * 4) + 2);
+			break;
+		case EF_IFC_GPIO_CLOCK:
+			priv->gpio_altfunc |= BIT((i * 4) + 3);
+			break;
+		case EF_IFC_DYNAMIC_SUSPEND:
+			priv->gpio_altfunc |= BIT(i * 4);
+			priv->gpio_altfunc |= BIT((i * 4) + 1);
+			priv->gpio_altfunc |= BIT((i * 4) + 2);
+			priv->gpio_altfunc |= BIT((i * 4) + 3);
+			break;
+		}
+	}
+	/*
+	 * Like CP2102N, CP2108 has also no strict input and output pin
+	 * modes.
+	 * Do the same input mode emulation as CP2102N.
+	 */
+	for (i = 0; i < priv->gc.ngpio; ++i) {
+		/*
+		 * Set direction to "input" iff pin is open-drain and reset
+		 * value is 1.
+		 */
+		if (!(priv->gpio_pushpull & BIT(i)) && (gpio_latch & BIT(i)))
+			priv->gpio_input |= BIT(i);
+	}
+
+	return 0;
+}
+
 /*
  * This function is for configuring GPIO using shared pins, where other signals
  * are made unavailable by configuring the use of GPIO. This is believed to be
@@ -1649,6 +1825,15 @@  static int cp210x_gpio_init(struct usb_serial *serial)
 	case CP210X_PARTNUM_CP2102N_QFN20:
 		result = cp2102n_gpioconf_init(serial);
 		break;
+	case CP210X_PARTNUM_CP2108:
+		/*
+		 * The GPIOs are not tied to any specific port so onlu register
+		 * once for interface 0.
+		 */
+		if (cp210x_interface_num(serial) != 0)
+			return 0;
+		result = cp2108_gpio_init(serial);
+		break;
 	default:
 		return 0;
 	}