Sometimes it's necessary to set GPIO values synchronously, e.g.
when CPU's GPIOs go to a FPGA and the FPGA has no latch-enable line,
so intermediate values on GPIO lines may trigger unnecessary actions
by the FPGA.
Another usage is chip-select muxes, e.g. using X GPIOs as address lines
to mux 2^X chip-selects, and setting some amount of GPIOs at once may
be a huge win.
Note that it's not always possible to set up GPIOs synchronously, so
gpio_can_set_values_sync() call is implemented. Currently it checks
for two things:
1. Whether gpio_chip has .set_sync() callback;
2. Whether all passed GPIOs belong to one particular gpio_chip.
Someday we may want to implement chip-specific .can_set_sync() check,
but currently this isn't needed.
Signed-off-by: Anton Vorontsov <avoront...@ru.mvista.com>
---
drivers/gpio/gpiolib.c | 57 ++++++++++++++++++++++++++++++++++++++++++++
include/asm-generic/gpio.h | 8 ++++++
include/linux/gpio.h | 14 ++++++++++
3 files changed, 79 insertions(+), 0 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 51a8d41..cf714ad 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1067,6 +1067,53 @@ void __gpio_set_value(unsigned gpio, int value)
EXPORT_SYMBOL_GPL(__gpio_set_value);
/**
+ * __gpio_can_set_values_sync() - check if gpios can be set synchronously
+ * @num: amount of gpios
+ * @gpios: gpios in question
+ * Context: any
+ *
+ * This is used directly or indirectly to implement gpio_can_set_values_sync().
+ * It returns nonzero if an array of gpios can be set simultaneously.
+ */
+int __gpio_can_set_values_sync(unsigned num, unsigned *gpios)
+{
+ struct gpio_chip *chip;
+ unsigned i;
+
+ chip = gpio_to_chip(gpios[0]);
+ if (!chip->set_sync)
+ return 0;
+
+ for (i = 1; i < num; i++) {
+ if (chip != gpio_to_chip(gpios[i]))
+ return 0;
+ }
+
+ return 1;
+}
+EXPORT_SYMBOL_GPL(__gpio_can_set_values_sync);
+
+/**
+ * __gpio_set_values_sync() - assign gpios' values synchronously
+ * @num: amount of gpios
+ * @gpios: gpios whose value will be assigned
+ * @values: value to assign
+ * Context: any
+ *
+ * This is used directly or indirectly to implement gpio_set_values_sync().
+ * It invokes the associated gpio_chip.set_sync() method.
+ */
+void __gpio_set_values_sync(unsigned num, unsigned *gpios, int *values)
+{
+ struct gpio_chip *chip;
+
+ chip = gpio_to_chip(gpios[0]);
+ WARN_ON(extra_checks && chip->can_sleep);
+ chip->set_sync(chip, num, gpios, values);
+}
+EXPORT_SYMBOL_GPL(__gpio_set_values_sync);
+
+/**
* __gpio_cansleep() - report whether gpio value access will sleep
* @gpio: gpio in question
* Context: any
@@ -1129,6 +1176,16 @@ void gpio_set_value_cansleep(unsigned gpio, int value)
}
EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);
+void gpio_set_values_sync_cansleep(unsigned num, unsigned *gpios, int *values)
+{
+ struct gpio_chip *chip;
+
+ might_sleep_if(extra_checks);
+ chip = gpio_to_chip(gpios[0]);
+ chip->set_sync(chip, num, gpios, values);
+}
+EXPORT_SYMBOL_GPL(gpio_set_values_sync_cansleep);
+
#ifdef CONFIG_DEBUG_FS
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index d6c379d..c181623 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -88,6 +88,10 @@ struct gpio_chip {
unsigned offset, int value);
void (*set)(struct gpio_chip *chip,
unsigned offset, int value);
+ /* NOTE: _sync() version accepts gpios, not offsets. */
+ void (*set_sync)(struct gpio_chip *chip,
+ unsigned num, unsigned *gpios,
+ int *values);
int (*to_irq)(struct gpio_chip *chip,
unsigned offset);
@@ -121,6 +125,8 @@ extern int gpio_direction_output(unsigned gpio, int value);
extern int gpio_get_value_cansleep(unsigned gpio);
extern void gpio_set_value_cansleep(unsigned gpio, int value);
+extern void gpio_set_values_sync_cansleep(unsigned num, unsigned *gpios,
+ int *values);
/* A platform's <asm/gpio.h> code may want to inline the I/O calls when
@@ -129,6 +135,8 @@ extern void gpio_set_value_cansleep(unsigned gpio, int
value);
*/
extern int __gpio_get_value(unsigned gpio);
extern void __gpio_set_value(unsigned gpio, int value);
+extern int __gpio_can_set_values_sync(unsigned num, unsigned *gpios);
+extern void __gpio_set_values_sync(unsigned num, unsigned *gpios, int *values);
extern int __gpio_cansleep(unsigned gpio);
diff --git a/include/linux/gpio.h b/include/linux/gpio.h
index e10c49a..ff62c1e 100644
--- a/include/linux/gpio.h
+++ b/include/linux/gpio.h
@@ -62,6 +62,20 @@ static inline void gpio_set_value(unsigned gpio, int value)
WARN_ON(1);
}
+static inline int gpio_can_set_values_sync(unsigned num, unsigned *gpios)
+{
+ /* GPIO can never have been requested or set as output */
+ WARN_ON(1);
+ return 0;
+}
+
+static inline void gpio_set_values_sync(unsigned num, unsigned *gpios,
+ int *values)
+{
+ /* GPIO can never have been requested or set as output */
+ WARN_ON(1);
+}
+
static inline int gpio_cansleep(unsigned gpio)
{
/* GPIO can never have been requested or set as {in,out}put */
--
1.6.3.3
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