[PATCH 3/5] ACPI / gpio: Add hogging support

Mika Westerberg
2016-09-23T14:57:41Z

GPIO hogging means that the GPIO controller can "hog" and configure certain
GPIOs without need for a driver or userspace to do that. This is useful in
open-connected boards where BIOS cannot possibly know beforehand which
devices will be connected to the board.

This adds GPIO hogging mechanism to ACPI analogous to Device Tree.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
Documentation/acpi/gpio-properties.txt | 26 ++++++++++++
drivers/gpio/gpiolib-acpi.c | 72 ++++++++++++++++++++++++++++++++++
2 files changed, 98 insertions(+)

diff --git a/Documentation/acpi/gpio-properties.txt b/Documentation/acpi/gpio-properties.txt
index 7875974823ae..46df91c3512b 100644
--- a/Documentation/acpi/gpio-properties.txt
+++ b/Documentation/acpi/gpio-properties.txt
@@ -69,6 +69,32 @@ Example:
}
}

+- gpio-hog
+- output-high
+- output-low
+- input
+- line-name
+
+Example:
+
+ Name (_DSD, Package () {
+ // _DSD Hierarchical Properties Extension UUID
+ ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
+ Package () {
+ Package () {"hog-gpio8", "G8PU"}
+ }
+ })
+
+ Name (G8PU, Package () {
+ ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+ Package () {
+ Package () {"gpio-hog", 1},
+ Package () {"gpios", Package () {8, 0}},
+ Package () {"output-high", 1},
+ Package () {"line-name", "gpio8-pullup"},
+ }
+ })
+
See Documentation/devicetree/bindings/gpio/gpio.tx for more information
about these properties.

diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index 202cf1b842de..4e50f8f5d597 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c
@@ -14,6 +14,7 @@
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
+#include <linux/gpio/machine.h>
#include <linux/export.h>
#include <linux/acpi.h>
#include <linux/interrupt.h>
@@ -845,6 +846,76 @@ static void acpi_gpiochip_set_names(struct acpi_gpio_chip *achip)
kfree(names);
}

+struct gpio_desc *acpi_gpiochip_parse_own_gpio(struct acpi_gpio_chip *achip,
+ struct fwnode_handle *fwnode, const char **name, unsigned int *lflags,
+ unsigned int *dflags)
+{
+ struct gpio_chip *chip = achip->chip;
+ struct gpio_desc *desc;
+ u32 gpios[2];
+ int ret;
+
+ ret = fwnode_property_read_u32_array(fwnode, "gpios", gpios,
+ ARRAY_SIZE(gpios));
+ if (ret < 0)
+ return ERR_PTR(ret);
+
+ ret = acpi_gpiochip_pin_to_gpio_offset(chip->gpiodev, gpios[0]);
+ if (ret < 0)
+ return ERR_PTR(ret);
+
+ desc = gpiochip_get_desc(chip, ret);
+ if (IS_ERR(desc))
+ return desc;
+
+ *lflags = 0;
+ *dflags = 0;
+ *name = NULL;
+
+ if (gpios[1])
+ *lflags |= GPIO_ACTIVE_LOW;
+
+ if (fwnode_property_present(fwnode, "input"))
+ *dflags |= GPIOD_IN;
+ else if (fwnode_property_present(fwnode, "output-low"))
+ *dflags |= GPIOD_OUT_LOW;
+ else if (fwnode_property_present(fwnode, "output-high"))
+ *dflags |= GPIOD_OUT_HIGH;
+ else
+ return ERR_PTR(-EINVAL);
+
+ fwnode_property_read_string(fwnode, "line-name", name);
+
+ return desc;
+}
+
+static void acpi_gpiochip_scan_gpios(struct acpi_gpio_chip *achip)
+{
+ struct gpio_chip *chip = achip->chip;
+ struct fwnode_handle *fwnode;
+
+ device_for_each_child_node(chip->parent, fwnode) {
+ unsigned int lflags, dflags;
+ struct gpio_desc *desc;
+ const char *name;
+ int ret;
+
+ if (!fwnode_property_present(fwnode, "gpio-hog"))
+ continue;
+
+ desc = acpi_gpiochip_parse_own_gpio(achip, fwnode, &name,
+ &lflags, &dflags);
+ if (IS_ERR(desc))
+ continue;
+
+ ret = gpiod_hog(desc, name, lflags, dflags);
+ if (ret) {
+ dev_err(chip->parent, "Failed to hog GPIO\n");
+ return;
+ }
+ }
+}
+
void acpi_gpiochip_add(struct gpio_chip *chip)
{
struct acpi_gpio_chip *acpi_gpio;
@@ -879,6 +950,7 @@ void acpi_gpiochip_add(struct gpio_chip *chip)
acpi_gpiochip_set_names(acpi_gpio);

acpi_gpiochip_request_regions(acpi_gpio);
+ acpi_gpiochip_scan_gpios(acpi_gpio);
acpi_walk_dep_device_list(handle);
}

--
2.9.3