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gpiolib: allow simultaneous setting of multiple GPIO outputs

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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>
This commit is contained in:
Rojhalat Ibrahim 2014-11-04 17:12:06 +01:00 committed by Linus Walleij
parent b5b7b48743
commit 5f42424354
4 changed files with 237 additions and 0 deletions
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27
Documentation/gpio/consumer.txt
View file

@ -199,6 +199,33 @@ 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 functions set the output values of an array of GPIOs:
void gpiod_set_array(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array)
void gpiod_set_raw_array(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array)
void gpiod_set_array_cansleep(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.
Note that for optimal performance GPIOs belonging to the same chip should be
contiguous within the array of descriptors.
GPIOs mapped to IRQs
--------------------
GPIO lines can quite often be used as IRQs. You can get the IRQ number

168
drivers/gpio/gpiolib.c
View file

@ -1254,6 +1254,88 @@ static void _gpiod_set_raw_value(struct gpio_desc *desc, bool value)
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
@ -1298,6 +1380,48 @@ 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
* @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
@ -1457,6 +1581,50 @@ 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
* @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

38
include/linux/gpio/consumer.h
View file

@ -74,14 +74,24 @@ int gpiod_direction_output_raw(struct gpio_desc *desc, int value);
/* Value get/set from non-sleeping context */
int gpiod_get_value(const struct gpio_desc *desc);
void gpiod_set_value(struct gpio_desc *desc, int value);
void gpiod_set_array(unsigned int array_size,
struct gpio_desc **desc_array, int *value_array);
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);
void gpiod_set_array_cansleep(unsigned int array_size,
struct gpio_desc **desc_array,
int *value_array);
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);
@ -210,6 +220,13 @@ static inline void gpiod_set_value(struct gpio_desc *desc, int value)
/* GPIO can never have been requested */
WARN_ON(1);
}
static inline void gpiod_set_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_raw_value(const struct gpio_desc *desc)
{
/* GPIO can never have been requested */
@ -221,6 +238,13 @@ static inline void gpiod_set_raw_value(struct gpio_desc *desc, int value)
/* GPIO can never have been requested */
WARN_ON(1);
}
static inline 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)
{
@ -233,6 +257,13 @@ static inline void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
/* GPIO can never have been requested */
WARN_ON(1);
}
static inline void gpiod_set_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_get_raw_value_cansleep(const struct gpio_desc *desc)
{
/* GPIO can never have been requested */
@ -245,6 +276,13 @@ static inline void gpiod_set_raw_value_cansleep(struct gpio_desc *desc,
/* GPIO can never have been requested */
WARN_ON(1);
}
static inline 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)
{

4
include/linux/gpio/driver.h
View file

@ -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;
@ -89,6 +90,9 @@ struct gpio_chip {
unsigned offset);
void (*set)(struct gpio_chip *chip,
unsigned offset, int value);
void (*set_multiple)(struct gpio_chip *chip,
unsigned long *mask,
unsigned long *bits);
int (*set_debounce)(struct gpio_chip *chip,
unsigned offset,
unsigned debounce);