From: Manivannan Sadhasivam <m...@kernel.org>

Add gpiochip support for Maxlinear/Exar USB to serial converter
for controlling the available gpios.

Cc: Linus Walleij <linus.wall...@linaro.org>
Cc: linux-g...@vger.kernel.org
Reviewed-by: Linus Walleij <linus.wall...@linaro.org>
Signed-off-by: Manivannan Sadhasivam <m...@kernel.org>
---
 drivers/usb/serial/xr_serial.c | 197 ++++++++++++++++++++++++++++++++-
 1 file changed, 196 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/xr_serial.c b/drivers/usb/serial/xr_serial.c
index d607906e46ad..fa99e6bfffa2 100644
--- a/drivers/usb/serial/xr_serial.c
+++ b/drivers/usb/serial/xr_serial.c
@@ -7,6 +7,7 @@
  * Copyright (c) 2020 Manivannan Sadhasivam <m...@kernel.org>
  */
 
+#include <linux/gpio/driver.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>
@@ -32,6 +33,11 @@ struct xr_uart_regs {
 };
 
 struct xr_port_private {
+#ifdef CONFIG_GPIOLIB
+       struct gpio_chip gc;
+       bool gpio_registered;
+       u8 gpio_altfunc;
+#endif
        const struct xr_uart_regs *regs;
        u16 idProduct;
        u8 reg_width;
@@ -570,6 +576,194 @@ static void xr_break_ctl(struct tty_struct *tty, int 
break_state)
                   state);
 }
 
+#ifdef CONFIG_GPIOLIB
+
+static int xr_gpio_request(struct gpio_chip *gc, unsigned int offset)
+{
+       struct usb_serial_port *port = gpiochip_get_data(gc);
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+
+       /* Check if the requested GPIO is occupied */
+       if (port_priv->gpio_altfunc & BIT(offset))
+               return -ENODEV;
+
+       return 0;
+}
+
+static int xr_gpio_get(struct gpio_chip *gc, unsigned int gpio)
+{
+       struct usb_serial_port *port = gpiochip_get_data(gc);
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+       int ret;
+       u8 gpio_status;
+
+       ret = xr_get_reg(port, XR21V141X_UART_REG_BLOCK,
+                        port_priv->regs->gpio_status, &gpio_status);
+       if (ret)
+               return ret;
+
+       return !!(gpio_status & BIT(gpio));
+}
+
+static void xr_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
+{
+       struct usb_serial_port *port = gpiochip_get_data(gc);
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+
+       if (val)
+               xr_set_reg(port, XR21V141X_UART_REG_BLOCK,
+                          port_priv->regs->gpio_set, BIT(gpio));
+       else
+               xr_set_reg(port, XR21V141X_UART_REG_BLOCK,
+                          port_priv->regs->gpio_clr, BIT(gpio));
+}
+
+static int xr_gpio_direction_get(struct gpio_chip *gc, unsigned int gpio)
+{
+       struct usb_serial_port *port = gpiochip_get_data(gc);
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+       int ret;
+       u8 gpio_dir;
+
+       ret = xr_get_reg(port, XR21V141X_UART_REG_BLOCK,
+                        port_priv->regs->gpio_dir, &gpio_dir);
+       if (ret)
+               return ret;
+
+       /* Logic 0 = input and Logic 1 = output */
+       return !(gpio_dir & BIT(gpio));
+}
+
+static int xr_gpio_direction_input(struct gpio_chip *gc, unsigned int gpio)
+{
+       struct usb_serial_port *port = gpiochip_get_data(gc);
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+       int ret;
+       u8 gpio_dir;
+
+       ret = xr_get_reg(port, XR21V141X_UART_REG_BLOCK,
+                        port_priv->regs->gpio_dir, &gpio_dir);
+       if (ret)
+               return ret;
+
+       gpio_dir &= ~BIT(gpio);
+
+       return xr_set_reg(port, XR21V141X_UART_REG_BLOCK,
+                         port_priv->regs->gpio_dir, gpio_dir);
+}
+
+static int xr_gpio_direction_output(struct gpio_chip *gc, unsigned int gpio,
+                                   int val)
+{
+       struct usb_serial_port *port = gpiochip_get_data(gc);
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+       int ret;
+       u8 gpio_dir;
+
+       ret = xr_get_reg(port, XR21V141X_UART_REG_BLOCK,
+                        port_priv->regs->gpio_dir, &gpio_dir);
+       if (ret)
+               return ret;
+
+       gpio_dir |= BIT(gpio);
+
+       ret = xr_set_reg(port, XR21V141X_UART_REG_BLOCK,
+                        port_priv->regs->gpio_dir, gpio_dir);
+       if (ret)
+               return ret;
+
+       xr_gpio_set(gc, gpio, val);
+
+       return 0;
+}
+
+static int xr21v141x_gpio_init(struct usb_serial_port *port)
+{
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+       int ret;
+       u8 gpio_mode;
+
+       port_priv->gc.ngpio = 6;
+
+       ret = xr_get_reg(port, XR21V141X_UART_REG_BLOCK,
+                        port_priv->regs->gpio_mode, &gpio_mode);
+       if (ret)
+               return ret;
+
+       /* Mark all pins which are not in GPIO mode */
+       if (gpio_mode & UART_MODE_RTS_CTS)
+               port_priv->gpio_altfunc |= (BIT(4) | BIT(5));
+       else if (gpio_mode & UART_MODE_DTR_DSR)
+               port_priv->gpio_altfunc |= (BIT(2) | BIT(3));
+       else if (gpio_mode & UART_MODE_RS485)
+               port_priv->gpio_altfunc |= BIT(5);
+       else if (gpio_mode & UART_MODE_RS485_ADDR)
+               port_priv->gpio_altfunc |= BIT(5);
+       else
+               port_priv->gpio_altfunc = 0; /* All GPIOs are available */
+
+       return ret;
+}
+
+static int xr_gpio_init(struct usb_serial_port *port)
+{
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+       int ret = 0;
+
+       /* Don't register gpiochip for interface 0 */
+       if (port->minor == 0)
+               return ret;
+
+       if (port_priv->idProduct == XR21V141X_ID)
+               ret = xr21v141x_gpio_init(port);
+
+       if (ret < 0)
+               return ret;
+
+       port_priv->gc.label = devm_kasprintf(&port->dev, GFP_KERNEL, "XR%04x",
+                                            port_priv->idProduct);
+       port_priv->gc.request = xr_gpio_request;
+       port_priv->gc.get_direction = xr_gpio_direction_get;
+       port_priv->gc.direction_input = xr_gpio_direction_input;
+       port_priv->gc.direction_output = xr_gpio_direction_output;
+       port_priv->gc.get = xr_gpio_get;
+       port_priv->gc.set = xr_gpio_set;
+       port_priv->gc.owner = THIS_MODULE;
+       port_priv->gc.parent = &port->dev;
+       port_priv->gc.base = -1;
+       port_priv->gc.can_sleep = true;
+
+       ret = gpiochip_add_data(&port_priv->gc, port);
+       if (!ret)
+               port_priv->gpio_registered = true;
+
+       return ret;
+}
+
+static void xr_gpio_remove(struct usb_serial_port *port)
+{
+       struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+
+       if (port_priv->gpio_registered) {
+               gpiochip_remove(&port_priv->gc);
+               port_priv->gpio_registered = false;
+       }
+}
+
+#else
+
+static int xr_gpio_init(struct usb_serial_port *port)
+{
+       return 0;
+}
+
+static void xr_gpio_remove(struct usb_serial_port *port)
+{
+       /* Nothing to do */
+}
+
+#endif
+
 static int xr_port_probe(struct usb_serial_port *port)
 {
        struct usb_serial *serial = port->serial;
@@ -589,13 +783,14 @@ static int xr_port_probe(struct usb_serial_port *port)
 
        usb_set_serial_port_data(port, port_priv);
 
-       return 0;
+       return xr_gpio_init(port);
 }
 
 static int xr_port_remove(struct usb_serial_port *port)
 {
        struct xr_port_private *port_priv = usb_get_serial_port_data(port);
 
+       xr_gpio_remove(port);
        kfree(port_priv);
 
        return 0;
-- 
2.17.1

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