Re: [PATCH v2] USB: serial: cp210x: Implement GPIO support for CP2102N

["Karoly Pados" <pados@pados.hu>]

Hello Johan,

I hope maybe after you come back from your vacation you can still
merge this into 4.19, I guess the merge window will still be open.

Given that there are
about another 5 weeks until 4.19rc1 merge window closes,
I didn't think I'd be late with this patch, I am sorry.
However, as already explained to you, it'd be very important
for me to get this patch at least into 4.19, as otherwise the
time I loose is much greater than a single release cycle (due
to distro cycles), and I have actually a crowdfunding product
depending on this.

Thank you for your understanding,
Karoly

July 18, 2018 11:20 PM, "Karoly Pados" <pados@pados.hu> wrote:

> This is v2 of the patch and addresses all feedback previously
> received from the maintainer. New input/output support stayed
> as discussed on the e-mail lists separately. CP2105 is also
> using the new code structure, but due to missing way to get
> default pin states after reset from the device, support
> for this device is basically still output-only as before, at
> least in name. But CP2105 and CP2102N paths are unified.
> 
> This patch is based on the latest patch series by Johan just
> submitted today.
> 
> Signed-off-by: Karoly Pados <pados@pados.hu>
> ---
> drivers/usb/serial/cp210x.c | 274 ++++++++++++++++++++++++++++++------
> 1 file changed, 232 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
> index 4a118eb13590..81f9d3e183c6 100644
> --- a/drivers/usb/serial/cp210x.c
> +++ b/drivers/usb/serial/cp210x.c
> @@ -224,9 +224,19 @@ 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;
> +
> + /*
> + * The following three fields are for devices that
> + * emulate input/output pins using open-drain/pushpull
> + * drive modes.
> + */
> + /* One bit for each GPIO, 1 if pin is pushpull */
> + u8 gpio_pushpull;
> + /* One bit for each GPIO, 1 if pin is not in GPIO mode */
> + u8 gpio_altfunc;
> + /* One bit for each GPIO, 1 if pin direction is input */
> + u8 gpio_input;
> #endif
> u8 partnum;
> speed_t max_speed;
> @@ -343,6 +353,7 @@ 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
> @@ -452,6 +463,12 @@ 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;
> @@ -1308,21 +1325,29 @@ static void cp210x_break_ctl(struct tty_struct *tty, int break_state)
> }
> 
> #ifdef CONFIG_GPIOLIB
> +
> +/*
> + * Helper to determine if a specific serial device belongs to the cp2102n
> + * family of devices.
> + */
> +static bool cp210x_is_cp2102n(struct usb_serial *serial)
> +{
> + struct cp210x_serial_private *priv = usb_get_serial_data(serial);
> +
> + return (priv->partnum == CP210X_PARTNUM_CP2102N_QFN28) ||
> + (priv->partnum == CP210X_PARTNUM_CP2102N_QFN24) ||
> + (priv->partnum == CP210X_PARTNUM_CP2102N_QFN20);
> +}
> +
> 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)) {
> + dev_warn(&serial->interface->dev,
> + "Cannot control GPIO with active alternate function.\n");
> + return -ENODEV;
> }
> 
> return 0;
> @@ -1331,10 +1356,15 @@ static int cp210x_gpio_request(struct gpio_chip *gc, unsigned int offset)
> 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;
> @@ -1345,34 +1375,82 @@ 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 = 0;
> 
> - if (value == 1)
> - buf.state = BIT(gpio);
> - else
> - buf.state = 0;
> -
> + buf.state = (value == 1) ? BIT(gpio) : 0;
> 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 if (cp210x_is_cp2102n(serial)) {
> + 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.\n");
> }
> 
> 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;
> + } else if (cp210x_is_cp2102n(serial)) {
> + /* Push-pull pins cannot be changed to be inputs */
> + if (priv->gpio_pushpull & BIT(gpio)) {
> + dev_warn(&serial->interface->dev,
> + "Cannot change direction of a push-pull GPIO to input.\n");
> + return -EPERM;
> + }
> +
> + /* Make sure to release pin if it is being driven low */
> + cp210x_gpio_set(gc, gpio, 1);
> +
> + /* Note pin direction to ourselves */
> + priv->gpio_input |= BIT(gpio);
> +
> + return 0;
> + }
> +
> + return -EPERM;
> }
> 
> 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);
> +
> + /* Note pin direction to ourselves */
> + priv->gpio_input &= ~BIT(gpio);
> +
> + /* Set requested initial output value */
> + cp210x_gpio_set(gc, gpio, value);
> +
> return 0;
> }
> 
> @@ -1385,11 +1463,11 @@ 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;
> @@ -1402,13 +1480,14 @@ 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);
> int result;
> + u8 iface_config;
> 
> result = cp210x_read_vendor_block(serial, REQTYPE_DEVICE_TO_HOST,
> CP210X_GET_DEVICEMODE, &mode,
> @@ -1424,20 +1503,25 @@ 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)
> - return 0;
> + if (mode.sci == CP210X_PIN_MODE_MODEM) {
> + /* Mark all GPIOs of this interface as reserved */
> + priv->gpio_altfunc = 0xFF;
> + }
> 
> - 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;
> @@ -1445,6 +1529,118 @@ static int cp2105_shared_gpio_init(struct usb_serial *serial)
> return -ENODEV;
> }
> 
> + /* Mark all pins which are not in GPIO mode */
> + priv->gpio_altfunc = 0;
> + 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-xs
> a
> + */
> + 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 -EIO;
> + }
> +
> + 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 = 0;
> +
> + if (cp210x_is_cp2102n(serial))
> + result = cp2102n_gpioconf_init(serial);
> + else if (priv->partnum == CP210X_PARTNUM_CP2105)
> + result = cp2105_gpioconf_init(serial);
> + else
> + return 0;
> +
> + if (result < 0) {
> + dev_err(&serial->interface->dev,
> + "GPIO initialisation failed, continuing without GPIO support\n");
> + return result;
> + }
> +
> priv->gc.label = "cp210x";
> priv->gc.request = cp210x_gpio_request;
> priv->gc.get_direction = cp210x_gpio_direction_get;
> @@ -1477,7 +1673,7 @@ 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;
> }
> @@ -1588,13 +1784,7 @@ 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");
> - }
> - }
> + cp210x_gpio_init(serial);
> 
> return 0;
> }
> -- 
> 2.17.1