gpiolib: add support for disabling line bias

Allow pull up/down bias to be disabled, allowing the line to float
or to be biased only by external circuitry.
Use case is for where the bias has been applied previously, either
by default or by the user, but that setting may conflict with the
current use of the line.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index b7d7bb8bd20dd5f8b44d00f96ededb07aa54d9b0..9969116603066669fe3ea4daf9bf800dfb2629bb 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -424,6 +424,7 @@ struct linehandle_state {
        GPIOHANDLE_REQUEST_ACTIVE_LOW | \
        GPIOHANDLE_REQUEST_BIAS_PULL_UP | \
        GPIOHANDLE_REQUEST_BIAS_PULL_DOWN | \
+       GPIOHANDLE_REQUEST_BIAS_DISABLE | \
        GPIOHANDLE_REQUEST_OPEN_DRAIN | \
        GPIOHANDLE_REQUEST_OPEN_SOURCE)
 
@@ -555,12 +556,21 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
             (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
                return -EINVAL;
 
-       /* PULL_UP and PULL_DOWN flags only make sense for input mode. */
+       /* Bias flags only allowed for input mode. */
        if (!(lflags & GPIOHANDLE_REQUEST_INPUT) &&
-           ((lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP) ||
+           ((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) ||
+            (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP) ||
             (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)))
                return -EINVAL;
 
+       /* Only one bias flag can be set. */
+       if (((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) &&
+            (lflags & (GPIOHANDLE_REQUEST_BIAS_PULL_DOWN |
+                       GPIOHANDLE_REQUEST_BIAS_PULL_UP))) ||
+           ((lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) &&
+            (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
+               return -EINVAL;
+
        lh = kzalloc(sizeof(*lh), GFP_KERNEL);
        if (!lh)
                return -ENOMEM;
@@ -601,6 +611,8 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
                        set_bit(FLAG_OPEN_DRAIN, &desc->flags);
                if (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)
                        set_bit(FLAG_OPEN_SOURCE, &desc->flags);
+               if (lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE)
+                       set_bit(FLAG_BIAS_DISABLE, &desc->flags);
                if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)
                        set_bit(FLAG_PULL_DOWN, &desc->flags);
                if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)
@@ -925,6 +937,14 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
            (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE))
                return -EINVAL;
 
+       /* Only one bias flag can be set. */
+       if (((lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE) &&
+            (lflags & (GPIOHANDLE_REQUEST_BIAS_PULL_DOWN |
+                       GPIOHANDLE_REQUEST_BIAS_PULL_UP))) ||
+           ((lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN) &&
+            (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)))
+               return -EINVAL;
+
        le = kzalloc(sizeof(*le), GFP_KERNEL);
        if (!le)
                return -ENOMEM;
@@ -951,6 +971,8 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 
        if (lflags & GPIOHANDLE_REQUEST_ACTIVE_LOW)
                set_bit(FLAG_ACTIVE_LOW, &desc->flags);
+       if (lflags & GPIOHANDLE_REQUEST_BIAS_DISABLE)
+               set_bit(FLAG_BIAS_DISABLE, &desc->flags);
        if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_DOWN)
                set_bit(FLAG_PULL_DOWN, &desc->flags);
        if (lflags & GPIOHANDLE_REQUEST_BIAS_PULL_UP)
@@ -1108,6 +1130,8 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
                        lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE |
                                           GPIOLINE_FLAG_IS_OUT);
+               if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))
+                       lineinfo.flags |= GPIOLINE_FLAG_BIAS_DISABLE;
                if (test_bit(FLAG_PULL_DOWN, &desc->flags))
                        lineinfo.flags |= GPIOLINE_FLAG_BIAS_PULL_DOWN;
                if (test_bit(FLAG_PULL_UP, &desc->flags))
@@ -2807,6 +2831,7 @@ static bool gpiod_free_commit(struct gpio_desc *desc)
                clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
                clear_bit(FLAG_PULL_UP, &desc->flags);
                clear_bit(FLAG_PULL_DOWN, &desc->flags);
+               clear_bit(FLAG_BIAS_DISABLE, &desc->flags);
                clear_bit(FLAG_IS_HOGGED, &desc->flags);
                ret = true;
        }
@@ -2933,6 +2958,7 @@ static int gpio_set_config(struct gpio_chip *gc, unsigned offset,
        unsigned arg;
 
        switch (mode) {
+       case PIN_CONFIG_BIAS_DISABLE:
        case PIN_CONFIG_BIAS_PULL_DOWN:
        case PIN_CONFIG_BIAS_PULL_UP:
                arg = 1;
@@ -2946,6 +2972,26 @@ static int gpio_set_config(struct gpio_chip *gc, unsigned offset,
        return gc->set_config ? gc->set_config(gc, offset, config) : -ENOTSUPP;
 }
 
+static int gpio_set_bias(struct gpio_chip *chip, struct gpio_desc *desc)
+{
+       int bias = 0;
+       int ret = 0;
+
+       if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))
+               bias = PIN_CONFIG_BIAS_DISABLE;
+       else if (test_bit(FLAG_PULL_UP, &desc->flags))
+               bias = PIN_CONFIG_BIAS_PULL_UP;
+       else if (test_bit(FLAG_PULL_DOWN, &desc->flags))
+               bias = PIN_CONFIG_BIAS_PULL_DOWN;
+
+       if (bias) {
+               ret = gpio_set_config(chip, gpio_chip_hwgpio(desc), bias);
+               if (ret != -ENOTSUPP)
+                       return ret;
+       }
+       return 0;
+}
+
 /**
  * gpiod_direction_input - set the GPIO direction to input
  * @desc:      GPIO to set to input
@@ -2990,15 +3036,10 @@ int gpiod_direction_input(struct gpio_desc *desc)
                           __func__);
                return -EIO;
        }
-       if (ret == 0)
+       if (ret == 0) {
                clear_bit(FLAG_IS_OUT, &desc->flags);
-
-       if (test_bit(FLAG_PULL_UP, &desc->flags))
-               gpio_set_config(chip, gpio_chip_hwgpio(desc),
-                               PIN_CONFIG_BIAS_PULL_UP);
-       else if (test_bit(FLAG_PULL_DOWN, &desc->flags))
-               gpio_set_config(chip, gpio_chip_hwgpio(desc),
-                               PIN_CONFIG_BIAS_PULL_DOWN);
+               ret = gpio_set_bias(chip, desc);
+       }
 
        trace_gpio_direction(desc_to_gpio(desc), 1, ret);
 

diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index b8b10a409c7b9c6584e6e176d9246aec5c394258..ca9bc1e4803c2979c3ea3d68b1ce893b2d154ce5 100644 (file)
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -110,6 +110,7 @@ struct gpio_desc {
 #define FLAG_TRANSITORY 12     /* GPIO may lose value in sleep or reset */
 #define FLAG_PULL_UP    13     /* GPIO has pull up enabled */
 #define FLAG_PULL_DOWN  14     /* GPIO has pull down enabled */
+#define FLAG_BIAS_DISABLE    15        /* GPIO has pull disabled */
 
        /* Connection label */
        const char              *label;

diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h
index 39e6c7854d63d7df2a56299a6ae103cd7ad0e05b..7cc21c3b083977c8ed53b33c509c6ae2c6248368 100644 (file)
--- a/include/uapi/linux/gpio.h
+++ b/include/uapi/linux/gpio.h
@@ -35,6 +35,7 @@ struct gpiochip_info {
 #define GPIOLINE_FLAG_OPEN_SOURCE      (1UL << 4)
 #define GPIOLINE_FLAG_BIAS_PULL_UP     (1UL << 5)
 #define GPIOLINE_FLAG_BIAS_PULL_DOWN   (1UL << 6)
+#define GPIOLINE_FLAG_BIAS_DISABLE     (1UL << 7)
 
 /**
  * struct gpioline_info - Information about a certain GPIO line
@@ -66,6 +67,7 @@ struct gpioline_info {
 #define GPIOHANDLE_REQUEST_OPEN_SOURCE (1UL << 4)
 #define GPIOHANDLE_REQUEST_BIAS_PULL_UP        (1UL << 5)
 #define GPIOHANDLE_REQUEST_BIAS_PULL_DOWN      (1UL << 6)
+#define GPIOHANDLE_REQUEST_BIAS_DISABLE        (1UL << 7)
 
 /**
  * struct gpiohandle_request - Information about a GPIO handle request