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USB: serial: cp210x: implement GPIO support for CP2102N
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This patch adds GPIO support for CP2102N devices.

It introduces new generic code to support emulating separate
input and outputs directions even though these devices
only know output modes (open-drain and pushpull). Existing
GPIO support for CP2105 has been migrated over to the new
code structure.

Only limitation is that for the QFN28 variant, only 4 out of
7 GPIOs are supported. This is because the config array
locations of the last 3 pins are not documented, and reverse
engineering revealed offsets that conflicted with other
documented functions. Hence we'll play it safe instead
until somebody clears this up further.

Signed-off-by: Karoly Pados <[email protected]>
[ johan: fix style issues and a couple of minor bugs; use Karoly's
         updated commit message ]
Acked-by: Martyn Welch <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>
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@jhovold
Karoly Pados authored and jhovold committed Jul 20, 2018
1 parent 5edb65a commit c8acfe0
Showing 1 changed file with 209 additions and 36 deletions.
245 changes: 209 additions & 36 deletions drivers/usb/serial/cp210x.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -224,9 +224,10 @@ MODULE_DEVICE_TABLE(usb, id_table);
struct cp210x_serial_private {
#ifdef CONFIG_GPIOLIB
struct gpio_chip gc;
u8 config;
u8 gpio_mode;
bool gpio_registered;
u8 gpio_pushpull;
u8 gpio_altfunc;
u8 gpio_input;
#endif
u8 partnum;
speed_t max_speed;
Expand Down Expand Up @@ -343,6 +344,7 @@ static struct usb_serial_driver * const serial_drivers[] = {
#define CONTROL_WRITE_RTS 0x0200

/* CP210X_VENDOR_SPECIFIC values */
#define CP210X_READ_2NCONFIG 0x000E
#define CP210X_READ_LATCH 0x00C2
#define CP210X_GET_PARTNUM 0x370B
#define CP210X_GET_PORTCONFIG 0x370C
Expand Down Expand Up @@ -452,6 +454,12 @@ struct cp210x_config {
#define CP2105_GPIO1_RXLED_MODE BIT(1)
#define CP2105_GPIO1_RS485_MODE BIT(2)

/* CP2102N configuration array indices */
#define CP210X_2NCONFIG_CONFIG_VERSION_IDX 2
#define CP210X_2NCONFIG_GPIO_MODE_IDX 581
#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 {
u8 mask;
Expand Down Expand Up @@ -1313,28 +1321,24 @@ static int cp210x_gpio_request(struct gpio_chip *gc, unsigned int offset)
struct usb_serial *serial = gpiochip_get_data(gc);
struct cp210x_serial_private *priv = usb_get_serial_data(serial);

switch (offset) {
case 0:
if (priv->config & CP2105_GPIO0_TXLED_MODE)
return -ENODEV;
break;
case 1:
if (priv->config & (CP2105_GPIO1_RXLED_MODE |
CP2105_GPIO1_RS485_MODE))
return -ENODEV;
break;
}
if (priv->gpio_altfunc & BIT(offset))
return -ENODEV;

return 0;
}

static int cp210x_gpio_get(struct gpio_chip *gc, unsigned int gpio)
{
struct usb_serial *serial = gpiochip_get_data(gc);
struct cp210x_serial_private *priv = usb_get_serial_data(serial);
u8 req_type = REQTYPE_DEVICE_TO_HOST;
int result;
u8 buf;

result = cp210x_read_vendor_block(serial, REQTYPE_INTERFACE_TO_HOST,
if (priv->partnum == CP210X_PARTNUM_CP2105)
req_type = REQTYPE_INTERFACE_TO_HOST;

result = cp210x_read_vendor_block(serial, req_type,
CP210X_READ_LATCH, &buf, sizeof(buf));
if (result < 0)
return result;
Expand All @@ -1345,7 +1349,9 @@ static int cp210x_gpio_get(struct gpio_chip *gc, unsigned int gpio)
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;
int result;

if (value == 1)
buf.state = BIT(gpio);
Expand All @@ -1354,25 +1360,68 @@ static void cp210x_gpio_set(struct gpio_chip *gc, unsigned int gpio, int value)

buf.mask = BIT(gpio);

cp210x_write_vendor_block(serial, REQTYPE_HOST_TO_INTERFACE,
CP210X_WRITE_LATCH, &buf, sizeof(buf));
if (priv->partnum == CP210X_PARTNUM_CP2105) {
result = cp210x_write_vendor_block(serial,
REQTYPE_HOST_TO_INTERFACE,
CP210X_WRITE_LATCH, &buf,
sizeof(buf));
} else {
u16 wIndex = buf.state << 8 | buf.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);
}

if (result < 0) {
dev_err(&serial->interface->dev, "failed to set GPIO value: %d\n",
result);
}
}

static int cp210x_gpio_direction_get(struct gpio_chip *gc, unsigned int gpio)
{
/* Hardware does not support an input mode */
return 0;
struct usb_serial *serial = gpiochip_get_data(gc);
struct cp210x_serial_private *priv = usb_get_serial_data(serial);

return priv->gpio_input & BIT(gpio);
}

static int cp210x_gpio_direction_input(struct gpio_chip *gc, unsigned int gpio)
{
/* Hardware does not support an input mode */
return -ENOTSUPP;
struct usb_serial *serial = gpiochip_get_data(gc);
struct cp210x_serial_private *priv = usb_get_serial_data(serial);

if (priv->partnum == CP210X_PARTNUM_CP2105) {
/* hardware does not support an input mode */
return -ENOTSUPP;
}

/* push-pull pins cannot be changed to be inputs */
if (priv->gpio_pushpull & BIT(gpio))
return -EINVAL;

/* make sure to release pin if it is being driven low */
cp210x_gpio_set(gc, gpio, 1);

priv->gpio_input |= BIT(gpio);

return 0;
}

static int cp210x_gpio_direction_output(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);

priv->gpio_input &= ~BIT(gpio);
cp210x_gpio_set(gc, gpio, value);

return 0;
}

Expand All @@ -1385,11 +1434,11 @@ static int cp210x_gpio_set_config(struct gpio_chip *gc, unsigned int gpio,

/* Succeed only if in correct mode (this can't be set at runtime) */
if ((param == PIN_CONFIG_DRIVE_PUSH_PULL) &&
(priv->gpio_mode & BIT(gpio)))
(priv->gpio_pushpull & BIT(gpio)))
return 0;

if ((param == PIN_CONFIG_DRIVE_OPEN_DRAIN) &&
!(priv->gpio_mode & BIT(gpio)))
!(priv->gpio_pushpull & BIT(gpio)))
return 0;

return -ENOTSUPP;
Expand All @@ -1402,12 +1451,13 @@ static int cp210x_gpio_set_config(struct gpio_chip *gc, unsigned int gpio,
* this driver that provide GPIO do so in a way that does not impact other
* signals and are thus expected to have very different initialisation.
*/
static int cp2105_shared_gpio_init(struct usb_serial *serial)
static int cp2105_gpioconf_init(struct usb_serial *serial)
{
struct cp210x_serial_private *priv = usb_get_serial_data(serial);
struct cp210x_pin_mode mode;
struct cp210x_config config;
u8 intf_num = cp210x_interface_num(serial);
u8 iface_config;
int result;

result = cp210x_read_vendor_block(serial, REQTYPE_DEVICE_TO_HOST,
Expand All @@ -1424,27 +1474,152 @@ static int cp2105_shared_gpio_init(struct usb_serial *serial)

/* 2 banks of GPIO - One for the pins taken from each serial port */
if (intf_num == 0) {
if (mode.eci == CP210X_PIN_MODE_MODEM)
if (mode.eci == CP210X_PIN_MODE_MODEM) {
/* mark all GPIOs of this interface as reserved */
priv->gpio_altfunc = 0xff;
return 0;
}

priv->config = config.eci_cfg;
priv->gpio_mode = (u8)((le16_to_cpu(config.gpio_mode) &
iface_config = config.eci_cfg;
priv->gpio_pushpull = (u8)((le16_to_cpu(config.gpio_mode) &
CP210X_ECI_GPIO_MODE_MASK) >>
CP210X_ECI_GPIO_MODE_OFFSET);
priv->gc.ngpio = 2;
} else if (intf_num == 1) {
if (mode.sci == CP210X_PIN_MODE_MODEM)
if (mode.sci == CP210X_PIN_MODE_MODEM) {
/* mark all GPIOs of this interface as reserved */
priv->gpio_altfunc = 0xff;
return 0;
}

priv->config = config.sci_cfg;
priv->gpio_mode = (u8)((le16_to_cpu(config.gpio_mode) &
iface_config = config.sci_cfg;
priv->gpio_pushpull = (u8)((le16_to_cpu(config.gpio_mode) &
CP210X_SCI_GPIO_MODE_MASK) >>
CP210X_SCI_GPIO_MODE_OFFSET);
priv->gc.ngpio = 3;
} else {
return -ENODEV;
}

/* mark all pins which are not in GPIO mode */
if (iface_config & CP2105_GPIO0_TXLED_MODE) /* GPIO 0 */
priv->gpio_altfunc |= BIT(0);
if (iface_config & (CP2105_GPIO1_RXLED_MODE | /* GPIO 1 */
CP2105_GPIO1_RS485_MODE))
priv->gpio_altfunc |= BIT(1);

/* driver implementation for CP2105 only supports outputs */
priv->gpio_input = 0;

return 0;
}

static int cp2102n_gpioconf_init(struct usb_serial *serial)
{
struct cp210x_serial_private *priv = usb_get_serial_data(serial);
const u16 config_size = 0x02a6;
u8 gpio_rst_latch;
u8 config_version;
u8 gpio_pushpull;
u8 *config_buf;
u8 gpio_latch;
u8 gpio_ctrl;
int result;
u8 i;

/*
* Retrieve device configuration from the device.
* The array received contains all customization settings done at the
* factory/manufacturer. Format of the array is documented at the
* time of writing at:
* https://www.silabs.com/community/interface/knowledge-base.entry.html/2017/03/31/cp2102n_setconfig-xsfa
*/
config_buf = kmalloc(config_size, GFP_KERNEL);
if (!config_buf)
return -ENOMEM;

result = cp210x_read_vendor_block(serial,
REQTYPE_DEVICE_TO_HOST,
CP210X_READ_2NCONFIG,
config_buf,
config_size);
if (result < 0) {
kfree(config_buf);
return result;
}

config_version = config_buf[CP210X_2NCONFIG_CONFIG_VERSION_IDX];
gpio_pushpull = config_buf[CP210X_2NCONFIG_GPIO_MODE_IDX];
gpio_ctrl = config_buf[CP210X_2NCONFIG_GPIO_CONTROL_IDX];
gpio_rst_latch = config_buf[CP210X_2NCONFIG_GPIO_RSTLATCH_IDX];

kfree(config_buf);

/* Make sure this is a config format we understand. */
if (config_version != 0x01)
return -ENOTSUPP;

/*
* We only support 4 GPIOs even on the QFN28 package, because
* config locations of GPIOs 4-6 determined using reverse
* engineering revealed conflicting offsets with other
* documented functions. So we'll just play it safe for now.
*/
priv->gc.ngpio = 4;

/*
* Get default pin states after reset. Needed so we can determine
* the direction of an open-drain pin.
*/
gpio_latch = (gpio_rst_latch >> 3) & 0x0f;

/* 0 indicates open-drain mode, 1 is push-pull */
priv->gpio_pushpull = (gpio_pushpull >> 3) & 0x0f;

/* 0 indicates GPIO mode, 1 is alternate function */
priv->gpio_altfunc = (gpio_ctrl >> 2) & 0x0f;

/*
* The CP2102N does not strictly has input and output pin modes,
* it only knows open-drain and push-pull modes which is set at
* factory. An open-drain pin can function both as an
* input or an output. We emulate input mode for open-drain pins
* by making sure they are not driven low, and we do not allow
* push-pull pins to be set as an input.
*/
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;
}

static int cp210x_gpio_init(struct usb_serial *serial)
{
struct cp210x_serial_private *priv = usb_get_serial_data(serial);
int result;

switch (priv->partnum) {
case CP210X_PARTNUM_CP2105:
result = cp2105_gpioconf_init(serial);
break;
case CP210X_PARTNUM_CP2102N_QFN28:
case CP210X_PARTNUM_CP2102N_QFN24:
case CP210X_PARTNUM_CP2102N_QFN20:
result = cp2102n_gpioconf_init(serial);
break;
default:
return 0;
}

if (result < 0)
return result;

priv->gc.label = "cp210x";
priv->gc.request = cp210x_gpio_request;
priv->gc.get_direction = cp210x_gpio_direction_get;
Expand Down Expand Up @@ -1477,7 +1652,7 @@ static void cp210x_gpio_remove(struct usb_serial *serial)

#else

static int cp2105_shared_gpio_init(struct usb_serial *serial)
static int cp210x_gpio_init(struct usb_serial *serial)
{
return 0;
}
Expand Down Expand Up @@ -1588,12 +1763,10 @@ static int cp210x_attach(struct usb_serial *serial)

cp210x_init_max_speed(serial);

if (priv->partnum == CP210X_PARTNUM_CP2105) {
result = cp2105_shared_gpio_init(serial);
if (result < 0) {
dev_err(&serial->interface->dev,
"GPIO initialisation failed, continuing without GPIO support\n");
}
result = cp210x_gpio_init(serial);
if (result < 0) {
dev_err(&serial->interface->dev, "GPIO initialisation failed: %d\n",
result);
}

return 0;
Expand Down

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