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 b7d7bb8..9969116 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -424,6 +424,7 @@
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 @@
(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 @@
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 @@
(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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
__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 b8b10a4..ca9bc1e 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -110,6 +110,7 @@
#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 39e6c78..7cc21c3 100644
--- a/include/uapi/linux/gpio.h
+++ b/include/uapi/linux/gpio.h
@@ -35,6 +35,7 @@
#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 @@
#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
