gpiolib: allow simultaneous setting of multiple GPIO outputs
Introduce new functions gpiod_set_array & gpiod_set_raw_array to the consumer
interface which allow 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
20 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.
Change log:
v6: - rebase on current linux-gpio devel branch
v5: - check can_sleep property per chip
- remove superfluous checks
- supplement documentation
v4: - add gpiod_set_array function for setting logical values
- change interface of the set_multiple driver function to use
unsigned long as type for the bit fields
- use generic bitops (which also use unsigned long for bit fields)
- do not use ARCH_NR_GPIOS any more
v3: - add documentation
- change commit message
v2: - use descriptor interface
- allow arbitrary groups of GPIOs spanning multiple chips
Signed-off-by: Rojhalat Ibrahim <imr@rtschenk.de>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 50e18a4..eb739a5 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1254,6 +1254,88 @@
chip->set(chip, gpio_chip_hwgpio(desc), value);
}
+/*
+ * set multiple outputs on the same chip;
+ * use the chip's set_multiple function if available;
+ * otherwise set the outputs sequentially;
+ * @mask: bit mask array; one bit per output; BITS_PER_LONG bits per word
+ * defines which outputs are to be changed
+ * @bits: bit value array; one bit per output; BITS_PER_LONG bits per word
+ * defines the values the outputs specified by mask are to be set to
+ */
+static void gpio_chip_set_multiple(struct gpio_chip *chip,
+ unsigned long *mask, unsigned long *bits)
+{
+ if (chip->set_multiple) {
+ chip->set_multiple(chip, mask, bits);
+ } else {
+ int i;
+ for (i = 0; i < chip->ngpio; i++) {
+ if (mask[BIT_WORD(i)] == 0) {
+ /* no more set bits in this mask word;
+ * skip ahead to the next word */
+ i = (BIT_WORD(i) + 1) * BITS_PER_LONG - 1;
+ continue;
+ }
+ /* set outputs if the corresponding mask bit is set */
+ if (__test_and_clear_bit(i, mask)) {
+ chip->set(chip, i, test_bit(i, bits));
+ }
+ }
+ }
+}
+
+static void gpiod_set_array_priv(bool raw, bool can_sleep,
+ unsigned int array_size,
+ struct gpio_desc **desc_array,
+ int *value_array)
+{
+ int i = 0;
+
+ while (i < array_size) {
+ struct gpio_chip *chip = desc_array[i]->chip;
+ unsigned long mask[BITS_TO_LONGS(chip->ngpio)];
+ unsigned long bits[BITS_TO_LONGS(chip->ngpio)];
+ int count = 0;
+
+ if (!can_sleep) {
+ WARN_ON(chip->can_sleep);
+ }
+ memset(mask, 0, sizeof(mask));
+ do {
+ struct gpio_desc *desc = desc_array[i];
+ int hwgpio = gpio_chip_hwgpio(desc);
+ int value = value_array[i];
+
+ if (!raw && test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+ value = !value;
+ trace_gpio_value(desc_to_gpio(desc), 0, value);
+ /*
+ * collect all normal outputs belonging to the same chip
+ * open drain and open source outputs are set individually
+ */
+ 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 {
+ __set_bit(hwgpio, mask);
+ if (value) {
+ __set_bit(hwgpio, bits);
+ } else {
+ __clear_bit(hwgpio, bits);
+ }
+ count++;
+ }
+ i++;
+ } while ((i < array_size) && (desc_array[i]->chip == chip));
+ /* push collected bits to outputs */
+ 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
@@ -1299,6 +1381,48 @@
EXPORT_SYMBOL_GPL(gpiod_set_value);
/**
+ * gpiod_set_raw_array() - assign values to an array of GPIOs
+ * @array_size: number of elements in the descriptor / value arrays
+ * @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;
+ gpiod_set_array_priv(true, false, array_size, desc_array, value_array);
+}
+EXPORT_SYMBOL_GPL(gpiod_set_raw_array);
+
+/**
+ * gpiod_set_array() - assign values to an array of GPIOs
+ * @array_size: number of elements in the descriptor / value arrays
+ * @desc_array: array of GPIO descriptors whose values will be assigned
+ * @value_array: array of values to assign
+ *
+ * Set the logical values of the GPIOs, i.e. taking their ACTIVE_LOW status
+ * into account.
+ *
+ * This function should be called from contexts where we cannot sleep, and will
+ * complain if the GPIO chip functions potentially sleep.
+ */
+void gpiod_set_array(unsigned int array_size,
+ struct gpio_desc **desc_array, int *value_array)
+{
+ if (!desc_array)
+ return;
+ gpiod_set_array_priv(false, false, array_size, desc_array, value_array);
+}
+EXPORT_SYMBOL_GPL(gpiod_set_array);
+
+/**
* gpiod_cansleep() - report whether gpio value access may sleep
* @desc: gpio to check
*
@@ -1458,6 +1582,50 @@
EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
/**
+ * gpiod_set_raw_array_cansleep() - assign values to an array of GPIOs
+ * @array_size: number of elements in the descriptor / value arrays
+ * @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_array_priv(true, true, array_size, desc_array, value_array);
+}
+EXPORT_SYMBOL_GPL(gpiod_set_raw_array_cansleep);
+
+/**
+ * gpiod_set_array_cansleep() - assign values to an array of GPIOs
+ * @array_size: number of elements in the descriptor / value arrays
+ * @desc_array: array of GPIO descriptors whose values will be assigned
+ * @value_array: array of values to assign
+ *
+ * Set the logical values of the GPIOs, i.e. taking their ACTIVE_LOW status
+ * into account.
+ *
+ * This function is to be called from contexts that can sleep.
+ */
+void gpiod_set_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_array_priv(false, true, array_size, desc_array, value_array);
+}
+EXPORT_SYMBOL_GPL(gpiod_set_array_cansleep);
+
+/**
* gpiod_add_lookup_table() - register GPIO device consumers
* @table: table of consumers to register
*/