gpio / ACPI: Add support for _DSD device properties

With release of ACPI 5.1 and _DSD method we can finally name GPIOs (and
other things as well) returned by _CRS. Previously we were only able to
use integer index to find the corresponding GPIO, which is pretty error
prone if the order changes.

With _DSD we can now query GPIOs using name instead of an integer index,
like the below example shows:

  // Bluetooth device with reset and shutdown GPIOs
  Device (BTH)
  {
      Name (_HID, ...)

      Name (_CRS, ResourceTemplate ()
      {
          GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
                  "\\_SB.GPO0", 0, ResourceConsumer) {15}
          GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
                  "\\_SB.GPO0", 0, ResourceConsumer) {27, 31}
      })

      Name (_DSD, Package ()
      {
          ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
          Package ()
	  {
              Package () {"reset-gpio", Package() {^BTH, 1, 1, 0 }},
              Package () {"shutdown-gpio", Package() {^BTH, 0, 0, 0 }},
          }
      })
  }

The format of the supported GPIO property is:

  Package () { "name", Package () { ref, index, pin, active_low }}

  ref - The device that has _CRS containing GpioIo()/GpioInt() resources,
        typically this is the device itself (BTH in our case).
  index - Index of the GpioIo()/GpioInt() resource in _CRS starting from zero.
  pin - Pin in the GpioIo()/GpioInt() resource. Typically this is zero.
  active_low - If 1 the GPIO is marked as active_low.

Since ACPI GpioIo() resource does not have field saying whether it is
active low or high, the "active_low" argument can be used here. Setting
it to 1 marks the GPIO as active low.

In our Bluetooth example the "reset-gpio" refers to the second GpioIo()
resource, second pin in that resource with the GPIO number of 31.

This patch implements necessary support to gpiolib for extracting GPIOs
using _DSD device properties.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 64 insertions, 14 deletions

diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index 05c6275da224..8aa6ca473748 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c
@@ -290,6 +290,7 @@ void acpi_gpiochip_free_interrupts(struct gpio_chip *chip)
 struct acpi_gpio_lookup {
         struct acpi_gpio_info info;
         int index;
+        int pin_index;
         struct gpio_desc *desc;
         int n;
 };
@@ -303,13 +304,24 @@ static int acpi_find_gpio(struct acpi_resource *ares, void *data)
 
         if (lookup->n++ == lookup->index && !lookup->desc) {
                 const struct acpi_resource_gpio *agpio = &ares->data.gpio;
+                int pin_index = lookup->pin_index;
+
+                if (pin_index >= agpio->pin_table_length)
+                        return 1;
 
                 lookup->desc = acpi_get_gpiod(agpio->resource_source.string_ptr,
-                                              agpio->pin_table[0]);
+                                              agpio->pin_table[pin_index]);
                 lookup->info.gpioint =
                         agpio->connection_type == ACPI_RESOURCE_GPIO_TYPE_INT;
-                lookup->info.active_low =
-                        agpio->polarity == ACPI_ACTIVE_LOW;
+
+                /*
+                 * ActiveLow is only specified for GpioInt resource. If
+                 * GpioIo is used then the only way to set the flag is
+                 * to use _DSD "gpios" property.
+                 */
+                if (lookup->info.gpioint)
+                        lookup->info.active_low =
+                                agpio->polarity == ACPI_ACTIVE_LOW;
         }
 
         return 1;
@@ -317,40 +329,75 @@ static int acpi_find_gpio(struct acpi_resource *ares, void *data)
 
 /**
  * acpi_get_gpiod_by_index() - get a GPIO descriptor from device resources
- * @dev: pointer to a device to get GPIO from
+ * @adev: pointer to a ACPI device to get GPIO from
+ * @propname: Property name of the GPIO (optional)
  * @index: index of GpioIo/GpioInt resource (starting from %0)
  * @info: info pointer to fill in (optional)
  *
- * Function goes through ACPI resources for @dev and based on @index looks
+ * Function goes through ACPI resources for @adev and based on @index looks
  * up a GpioIo/GpioInt resource, translates it to the Linux GPIO descriptor,
  * and returns it. @index matches GpioIo/GpioInt resources only so if there
  * are total %3 GPIO resources, the index goes from %0 to %2.
  *
+ * If @propname is specified the GPIO is looked using device property. In
+ * that case @index is used to select the GPIO entry in the property value
+ * (in case of multiple).
+ *
  * If the GPIO cannot be translated or there is an error an ERR_PTR is
  * returned.
  *
  * Note: if the GPIO resource has multiple entries in the pin list, this
  * function only returns the first.
  */
-struct gpio_desc *acpi_get_gpiod_by_index(struct device *dev, int index,
+struct gpio_desc *acpi_get_gpiod_by_index(struct acpi_device *adev,
+                                          const char *propname, int index,
                                           struct acpi_gpio_info *info)
 {
         struct acpi_gpio_lookup lookup;
         struct list_head resource_list;
-        struct acpi_device *adev;
-        acpi_handle handle;
+        bool active_low = false;
         int ret;
 
-        if (!dev)
-                return ERR_PTR(-EINVAL);
-
-        handle = ACPI_HANDLE(dev);
-        if (!handle || acpi_bus_get_device(handle, &adev))
+        if (!adev)
                 return ERR_PTR(-ENODEV);
 
         memset(&lookup, 0, sizeof(lookup));
         lookup.index = index;
 
+        if (propname) {
+                struct acpi_reference_args args;
+
+                dev_dbg(&adev->dev, "GPIO: looking up %s\n", propname);
+
+                memset(&args, 0, sizeof(args));
+                ret = acpi_dev_get_property_reference(adev, propname, NULL,
+                                                      index, &args);
+                if (ret)
+                        return ERR_PTR(ret);
+
+                /*
+                 * The property was found and resolved so need to
+                 * lookup the GPIO based on returned args instead.
+                 */
+                adev = args.adev;
+                if (args.nargs >= 2) {
+                        lookup.index = args.args[0];
+                        lookup.pin_index = args.args[1];
+                        /*
+                         * 3rd argument, if present is used to
+                         * specify active_low.
+                         */
+                        if (args.nargs >= 3)
+                                active_low = !!args.args[2];
+                }
+
+                dev_dbg(&adev->dev, "GPIO: _DSD returned %s %zd %llu %llu %llu\n",
+                        dev_name(&adev->dev), args.nargs,
+                        args.args[0], args.args[1], args.args[2]);
+        } else {
+                dev_dbg(&adev->dev, "GPIO: looking up %d in _CRS\n", index);
+        }
+
         INIT_LIST_HEAD(&resource_list);
         ret = acpi_dev_get_resources(adev, &resource_list, acpi_find_gpio,
                                      &lookup);
@@ -359,8 +406,11 @@ struct gpio_desc *acpi_get_gpiod_by_index(struct device *dev, int index,
 
         acpi_dev_free_resource_list(&resource_list);
 
-        if (lookup.desc && info)
+        if (lookup.desc && info) {
                 *info = lookup.info;
+                if (active_low)
+                        info->active_low = active_low;
+        }
 
         return lookup.desc ? lookup.desc : ERR_PTR(-ENOENT);
 }