Introduce a new function gpiod_set_raw_array to the consumer interface which
allows setting multiple outputs with just one function call. Also add an
optional set_multiple function to the driver interface. Without an
implementation of that function in the chip driver outputs are set
sequentially.
Implementing the set_multiple function in a chip driver allows for:
- Improved performance for certain use cases. The original motivation for this
was the task of configuring an FPGA. In that specific case, where 9 GPIO
lines have to be set many times, configuration time goes down from 48 s to
19 s when using the new function.
- Simultaneous glitch-free setting of multiple pins on any kind of parallel
bus attached to GPIOs provided they all reside on the same chip and bank.
Limitations:
- Performance is only improved for normal high-low outputs. Open drain and
open source outputs are always set separately from each other. Those kinds
of outputs could probably be accelerated in a similar way if we could
forgo the error checking when setting GPIO directions.
- There is no gpiod_set_array function that regards the ACTIVE_LOW bits.
The raw function should be sufficient for many use cases. So I avoided
the code duplication the other functions would require.
Signed-off-by: Rojhalat Ibrahim <[email protected]>
---
Change log:
v3: - add documentation
- change commit message
v2: - use descriptor interface
- allow arbitrary groups of GPIOs spanning multiple chips
Documentation/gpio/consumer.txt | 17 ++++++
drivers/gpio/gpiolib.c | 116 ++++++++++++++++++++++++++++++++++++++++
include/linux/gpio/consumer.h | 18 +++++++
include/linux/gpio/driver.h | 3 ++
4 files changed, 154 insertions(+)
diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
index 09854fe..affcd9b 100644
--- a/Documentation/gpio/consumer.txt
+++ b/Documentation/gpio/consumer.txt
@@ -163,6 +163,23 @@ The active-low state of a GPIO can also be queried using
the following call:
Note that these functions should only be used with great moderation ; a driver
should not have to care about the physical line level.
+Set multiple GPIO outputs with a single function call
+-----------------------------------------------------
+The following two functions set the raw output values of an array of GPIOs:
+
+ void gpiod_set_raw_array(unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array)
+ void gpiod_set_raw_array_cansleep(unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array)
+
+The array can be an arbitrary set of GPIOs. The functions will try to set
+GPIOs belonging to the same bank or chip simultaneously if supported by the
+corresponding chip driver. In that case a significantly improved performance
+can be expected. If simultaneous setting is not possible the GPIOs will be set
+sequentially.
+
GPIOs mapped to IRQs
--------------------
GPIO lines can quite often be used as IRQs. You can get the IRQ number
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f48817d..ee67ef1 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2345,6 +2345,77 @@ static void _gpiod_set_raw_value(struct gpio_desc *desc,
bool value)
chip->set(chip, gpio_chip_hwgpio(desc), value);
}
+static void _gpio_chip_set_multiple(struct gpio_chip *chip,
+ u32 mask[ARCH_NR_GPIOS/32],
+ u32 bits[ARCH_NR_GPIOS/32])
+{
+ if (chip->set_multiple) {
+ chip->set_multiple(chip, mask, bits);
+ } else {
+ int i;
+ for (i = 0; i < ARCH_NR_GPIOS; i++) {
+ if (i > chip->ngpio - 1)
+ break;
+ if (mask[i/32] == 0) {
+ /* skip ahead */
+ i = (i/32 + 1) * 32 - 1;
+ continue;
+ }
+ if (mask[i/32] & (1 << (i % 32))) {
+ chip->set(chip, i, (bits[i/32] >> (i % 32)) &
1);
+ mask[i/32] &= ~(1 << (i % 32));
+ }
+ }
+ }
+}
+
+static void _gpiod_set_raw_array(unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array)
+{
+ struct gpio_chip *chip = desc_array[0]->chip;
+ u32 mask[ARCH_NR_GPIOS/32];
+ u32 bits[ARCH_NR_GPIOS/32];
+ int count = 0;
+ int i;
+
+ memset(mask, 0, sizeof(mask));
+ for (i = 0; i < array_size; i++) {
+ struct gpio_desc *desc = desc_array[i];
+ int hwgpio = gpio_chip_hwgpio(desc);
+ int value = value_array[i];
+
+ /* another chip; push collected bits to outputs */
+ if (desc->chip != chip) {
+ if (count != 0) {
+ _gpio_chip_set_multiple(chip, mask, bits);
+ memset(mask, 0, sizeof(mask));
+ count = 0;
+ }
+ chip = desc->chip;
+ }
+ /* collect all normal outputs belonging to the same chip */
+ /* open drain and open source outputs are set individually */
+ trace_gpio_value(desc_to_gpio(desc), 0, value);
+ if (test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {
+ _gpio_set_open_drain_value(desc, value);
+ } else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) {
+ _gpio_set_open_source_value(desc, value);
+ } else {
+ mask[hwgpio/32] |= (1 << (hwgpio % 32));
+ if (value) {
+ bits[hwgpio/32] |= (1 << (hwgpio % 32));
+ } else {
+ bits[hwgpio/32] &= ~(1 << (hwgpio % 32));
+ }
+ count++;
+ }
+ }
+ if (count != 0) {
+ _gpio_chip_set_multiple(chip, mask, bits);
+ }
+}
+
/**
* gpiod_set_raw_value() - assign a gpio's raw value
* @desc: gpio whose value will be assigned
@@ -2390,6 +2461,30 @@ void gpiod_set_value(struct gpio_desc *desc, int value)
EXPORT_SYMBOL_GPL(gpiod_set_value);
/**
+ * gpiod_set_raw_array() - assign values to an array of GPIOs
+ * @desc_array: array of GPIO descriptors whose values will be assigned
+ * @value_array: array of values to assign
+ *
+ * Set the raw values of the GPIOs, i.e. the values of the physical lines
+ * without regard for their ACTIVE_LOW status.
+ *
+ * This function should be called from contexts where we cannot sleep, and will
+ * complain if the GPIO chip functions potentially sleep.
+ */
+void gpiod_set_raw_array(unsigned int array_size,
+ struct gpio_desc **desc_array, int *value_array)
+{
+ if (!desc_array)
+ return;
+ if (!desc_array[0])
+ return;
+ /* Should be using gpiod_set_raw_array_cansleep() */
+ WARN_ON(desc_array[0]->chip->can_sleep);
+ _gpiod_set_raw_array(array_size, desc_array, value_array);
+}
+EXPORT_SYMBOL_GPL(gpiod_set_raw_array);
+
+/**
* gpiod_cansleep() - report whether gpio value access may sleep
* @desc: gpio to check
*
@@ -2559,6 +2654,27 @@ void gpiod_set_value_cansleep(struct gpio_desc *desc,
int value)
EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
/**
+ * gpiod_set_raw_array_cansleep() - assign values to an array of GPIOs
+ * @desc_array: array of GPIO descriptors whose values will be assigned
+ * @value_array: array of values to assign
+ *
+ * Set the raw values of the GPIOs, i.e. the values of the physical lines
+ * without regard for their ACTIVE_LOW status.
+ *
+ * This function is to be called from contexts that can sleep.
+ */
+void gpiod_set_raw_array_cansleep(unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array)
+{
+ might_sleep_if(extra_checks);
+ if (!desc_array)
+ return;
+ _gpiod_set_raw_array(array_size, desc_array, value_array);
+}
+EXPORT_SYMBOL_GPL(gpiod_set_raw_array_cansleep);
+
+/**
* gpiod_add_lookup_table() - register GPIO device consumers
* @table: table of consumers to register
*/
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index bed128e..1d0bab3 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -42,12 +42,17 @@ int gpiod_get_value(const struct gpio_desc *desc);
void gpiod_set_value(struct gpio_desc *desc, int value);
int gpiod_get_raw_value(const struct gpio_desc *desc);
void gpiod_set_raw_value(struct gpio_desc *desc, int value);
+void gpiod_set_raw_array(unsigned int array_size,
+ struct gpio_desc **desc_array, int *value_array);
/* Value get/set from sleeping context */
int gpiod_get_value_cansleep(const struct gpio_desc *desc);
void gpiod_set_value_cansleep(struct gpio_desc *desc, int value);
int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc);
void gpiod_set_raw_value_cansleep(struct gpio_desc *desc, int value);
+void gpiod_set_raw_array_cansleep(unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array);
int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce);
@@ -150,6 +155,12 @@ static inline void gpiod_set_raw_value(struct gpio_desc
*desc, int value)
/* GPIO can never have been requested */
WARN_ON(1);
}
+void gpiod_set_raw_array(unsigned int array_size,
+ struct gpio_desc **desc_array, int *value_array)
+{
+ /* GPIO can never have been requested */
+ WARN_ON(1);
+}
static inline int gpiod_get_value_cansleep(const struct gpio_desc *desc)
{
@@ -174,6 +185,13 @@ static inline void gpiod_set_raw_value_cansleep(struct
gpio_desc *desc,
/* GPIO can never have been requested */
WARN_ON(1);
}
+void gpiod_set_raw_array_cansleep(unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array)
+{
+ /* GPIO can never have been requested */
+ WARN_ON(1);
+}
static inline int gpiod_set_debounce(struct gpio_desc *desc, unsigned debounce)
{
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 1827b43..d7968c8 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -32,6 +32,7 @@ struct seq_file;
* @get: returns value for signal "offset"; for output signals this
* returns either the value actually sensed, or zero
* @set: assigns output value for signal "offset"
+ * @set_multiple: assigns output values for multiple signals defined by "mask"
* @set_debounce: optional hook for setting debounce time for specified gpio in
* interrupt triggered gpio chips
* @to_irq: optional hook supporting non-static gpio_to_irq() mappings;
@@ -84,6 +85,8 @@ struct gpio_chip {
unsigned offset);
void (*set)(struct gpio_chip *chip,
unsigned offset, int value);
+ void (*set_multiple)(struct gpio_chip *chip,
+ u32 *mask, u32 *bits);
int (*set_debounce)(struct gpio_chip *chip,
unsigned offset,
unsigned debounce);
--
1.8.5.5
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