tty/serial: Add GPIOLIB helpers for controlling modem lines

This patch add some helpers to control modem lines (CTS/RTS/DSR...) via
GPIO.
This will be useful for many boards which have a serial controller that
only handle CTS/RTS pins (or even just RX/TX).

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 259 insertions, 0 deletions

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index d88c058634ff..4bf6d220357b 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1553,4 +1553,7 @@ config SERIAL_MEN_Z135
 
 endmenu
 
+config SERIAL_MCTRL_GPIO
+        tristate
+
 endif # TTY
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 712732b43917..0080cc362e09 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -92,3 +92,6 @@ obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o
 obj-$(CONFIG_SERIAL_RP2)        += rp2.o
 obj-$(CONFIG_SERIAL_FSL_LPUART) += fsl_lpuart.o
 obj-$(CONFIG_SERIAL_MEN_Z135)   += men_z135_uart.o
+
+# GPIOLIB helpers for modem control lines
+obj-$(CONFIG_SERIAL_MCTRL_GPIO) += serial_mctrl_gpio.o
diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
new file mode 100644
index 000000000000..bf9560ffe3f4
--- /dev/null
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -0,0 +1,143 @@
+/*
+ * Helpers for controlling modem lines via GPIO
+ *
+ * Copyright (C) 2014 Paratronic S.A.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <uapi/asm-generic/termios.h>
+
+#include "serial_mctrl_gpio.h"
+
+struct mctrl_gpios {
+        struct gpio_desc *gpio[UART_GPIO_MAX];
+};
+
+static const struct {
+        const char *name;
+        unsigned int mctrl;
+        bool dir_out;
+} mctrl_gpios_desc[UART_GPIO_MAX] = {
+        { "cts", TIOCM_CTS, false, },
+        { "dsr", TIOCM_DSR, false, },
+        { "dcd", TIOCM_CD, false, },
+        { "rng", TIOCM_RNG, false, },
+        { "rts", TIOCM_RTS, true, },
+        { "dtr", TIOCM_DTR, true, },
+        { "out1", TIOCM_OUT1, true, },
+        { "out2", TIOCM_OUT2, true, },
+};
+
+void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl)
+{
+        enum mctrl_gpio_idx i;
+
+        if (IS_ERR_OR_NULL(gpios))
+                return;
+
+        for (i = 0; i < UART_GPIO_MAX; i++)
+                if (!IS_ERR_OR_NULL(gpios->gpio[i]) &&
+                    mctrl_gpios_desc[i].dir_out)
+                        gpiod_set_value(gpios->gpio[i],
+                                        !!(mctrl & mctrl_gpios_desc[i].mctrl));
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_set);
+
+struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
+                                      enum mctrl_gpio_idx gidx)
+{
+        if (!IS_ERR_OR_NULL(gpios) && !IS_ERR_OR_NULL(gpios->gpio[gidx]))
+                return gpios->gpio[gidx];
+        else
+                return NULL;
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_to_gpiod);
+
+unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
+{
+        enum mctrl_gpio_idx i;
+
+        /*
+         * return it unchanged if the structure is not allocated
+         */
+        if (IS_ERR_OR_NULL(gpios))
+                return *mctrl;
+
+        for (i = 0; i < UART_GPIO_MAX; i++) {
+                if (!IS_ERR_OR_NULL(gpios->gpio[i]) &&
+                    !mctrl_gpios_desc[i].dir_out) {
+                        if (gpiod_get_value(gpios->gpio[i]))
+                                *mctrl |= mctrl_gpios_desc[i].mctrl;
+                        else
+                                *mctrl &= ~mctrl_gpios_desc[i].mctrl;
+                }
+        }
+
+        return *mctrl;
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_get);
+
+struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
+{
+        struct mctrl_gpios *gpios;
+        enum mctrl_gpio_idx i;
+        int err;
+
+        gpios = devm_kzalloc(dev, sizeof(*gpios), GFP_KERNEL);
+        if (!gpios)
+                return ERR_PTR(-ENOMEM);
+
+        for (i = 0; i < UART_GPIO_MAX; i++) {
+                gpios->gpio[i] = devm_gpiod_get_index(dev,
+                                                      mctrl_gpios_desc[i].name,
+                                                      idx);
+
+                /*
+                 * The GPIOs are maybe not all filled,
+                 * this is not an error.
+                 */
+                if (IS_ERR_OR_NULL(gpios->gpio[i]))
+                        continue;
+
+                if (mctrl_gpios_desc[i].dir_out)
+                        err = gpiod_direction_output(gpios->gpio[i], 0);
+                else
+                        err = gpiod_direction_input(gpios->gpio[i]);
+                if (err) {
+                        dev_dbg(dev, "Unable to set direction for %s GPIO",
+                                mctrl_gpios_desc[i].name);
+                        devm_gpiod_put(dev, gpios->gpio[i]);
+                        gpios->gpio[i] = NULL;
+                }
+        }
+
+        return gpios;
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_init);
+
+void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
+{
+        enum mctrl_gpio_idx i;
+
+        if (IS_ERR_OR_NULL(gpios))
+                return;
+
+        for (i = 0; i < UART_GPIO_MAX; i++)
+                if (!IS_ERR_OR_NULL(gpios->gpio[i]))
+                        devm_gpiod_put(dev, gpios->gpio[i]);
+        devm_kfree(dev, gpios);
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_free);
diff --git a/drivers/tty/serial/serial_mctrl_gpio.h b/drivers/tty/serial/serial_mctrl_gpio.h
new file mode 100644
index 000000000000..400ba0494a17
--- /dev/null
+++ b/drivers/tty/serial/serial_mctrl_gpio.h
@@ -0,0 +1,110 @@
+/*
+ * Helpers for controlling modem lines via GPIO
+ *
+ * Copyright (C) 2014 Paratronic S.A.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef __SERIAL_MCTRL_GPIO__
+#define __SERIAL_MCTRL_GPIO__
+
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+
+enum mctrl_gpio_idx {
+        UART_GPIO_CTS,
+        UART_GPIO_DSR,
+        UART_GPIO_DCD,
+        UART_GPIO_RNG,
+        UART_GPIO_RI = UART_GPIO_RNG,
+        UART_GPIO_RTS,
+        UART_GPIO_DTR,
+        UART_GPIO_OUT1,
+        UART_GPIO_OUT2,
+        UART_GPIO_MAX,
+};
+
+/*
+ * Opaque descriptor for modem lines controlled by GPIOs
+ */
+struct mctrl_gpios;
+
+#ifdef CONFIG_GPIOLIB
+
+/*
+ * Set state of the modem control output lines via GPIOs.
+ */
+void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl);
+
+/*
+ * Get state of the modem control output lines from GPIOs.
+ * The mctrl flags are updated and returned.
+ */
+unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl);
+
+/*
+ * Returns the associated struct gpio_desc to the modem line gidx
+ */
+struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
+                                      enum mctrl_gpio_idx gidx);
+
+/*
+ * Request and set direction of modem control lines GPIOs.
+ * devm_* functions are used, so there's no need to call mctrl_gpio_free().
+ * Returns a pointer to the allocated mctrl structure if ok, -ENOMEM on
+ * allocation error.
+ */
+struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx);
+
+/*
+ * Free the mctrl_gpios structure.
+ * Normally, this function will not be called, as the GPIOs will
+ * be disposed of by the resource management code.
+ */
+void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios);
+
+#else /* GPIOLIB */
+
+static inline
+void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl)
+{
+}
+
+static inline
+unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
+{
+        return *mctrl;
+}
+
+static inline
+struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
+                                      enum mctrl_gpio_idx gidx)
+{
+        return ERR_PTR(-ENOSYS);
+}
+
+static inline
+struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
+{
+        return ERR_PTR(-ENOSYS);
+}
+
+static inline
+void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
+{
+}
+
+#endif /* GPIOLIB */
+
+#endif