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Date:	Tue, 14 Oct 2014 15:44:03 +0200
From:	Grant Likely <grant.likely@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Aaron Lu <aaron.lu@...el.com>, devicetree@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Bryan Wu <cooloney@...il.com>, Arnd Bergmann <arnd@...db.de>,
	Darren Hart <dvhart@...ux.intel.com>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 06/13] gpio / ACPI: Add support for _DSD device
 properties

On Tue, 07 Oct 2014 02:15:18 +0200
, "Rafael J. Wysocki" <rjw@...ysocki.net>
 wrote:
> From: Mika Westerberg <mika.westerberg@...ux.intel.com>
> 
> 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.

Patch looks good, but please put the above description into
/Documentation until we've got a better place to document extra bindings.

g.

> 
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Acked-by: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/gpio/gpiolib-acpi.c | 78 +++++++++++++++++++++++++++++++++++++--------
>  drivers/gpio/gpiolib.c      | 30 ++++++++++++++---
>  drivers/gpio/gpiolib.h      |  7 ++--
>  3 files changed, 94 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
> index 687476f..b14c045 100644
> --- a/drivers/gpio/gpiolib-acpi.c
> +++ b/drivers/gpio/gpiolib-acpi.c
> @@ -293,6 +293,7 @@ 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;
>  };
> @@ -306,13 +307,24 @@ 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;
> @@ -320,40 +332,75 @@ 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);
> @@ -362,8 +409,11 @@ 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);
>  }
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index c68d037..4c86601 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1487,14 +1487,36 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
>  					unsigned int idx,
>  					enum gpio_lookup_flags *flags)
>  {
> +	static const char * const suffixes[] = { "gpios", "gpio" };
> +	struct acpi_device *adev = ACPI_COMPANION(dev);
>  	struct acpi_gpio_info info;
>  	struct gpio_desc *desc;
> +	char propname[32];
> +	int i;
>  
> -	desc = acpi_get_gpiod_by_index(dev, idx, &info);
> -	if (IS_ERR(desc))
> -		return desc;
> +	/* Try first from _DSD */
> +	for (i = 0; i < ARRAY_SIZE(suffixes); i++) {
> +		if (con_id && strcmp(con_id, "gpios")) {
> +			snprintf(propname, sizeof(propname), "%s-%s",
> +				 con_id, suffixes[i]);
> +		} else {
> +			snprintf(propname, sizeof(propname), "%s",
> +				 suffixes[i]);
> +		}
> +
> +		desc = acpi_get_gpiod_by_index(adev, propname, 0, &info);
> +		if (!IS_ERR(desc) || (PTR_ERR(desc) == -EPROBE_DEFER))
> +			break;
> +	}
> +
> +	/* Then from plain _CRS GPIOs */
> +	if (IS_ERR(desc)) {
> +		desc = acpi_get_gpiod_by_index(adev, NULL, idx, &info);
> +		if (IS_ERR(desc))
> +			return desc;
> +	}
>  
> -	if (info.gpioint && info.active_low)
> +	if (info.active_low)
>  		*flags |= GPIO_ACTIVE_LOW;
>  
>  	return desc;
> diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
> index 9db2b6a..e3a5211 100644
> --- a/drivers/gpio/gpiolib.h
> +++ b/drivers/gpio/gpiolib.h
> @@ -34,7 +34,8 @@ void acpi_gpiochip_remove(struct gpio_chip *chip);
>  void acpi_gpiochip_request_interrupts(struct gpio_chip *chip);
>  void acpi_gpiochip_free_interrupts(struct gpio_chip *chip);
>  
> -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);
>  #else
>  static inline void acpi_gpiochip_add(struct gpio_chip *chip) { }
> @@ -47,8 +48,8 @@ static inline void
>  acpi_gpiochip_free_interrupts(struct gpio_chip *chip) { }
>  
>  static inline struct gpio_desc *
> -acpi_get_gpiod_by_index(struct device *dev, int index,
> -			struct acpi_gpio_info *info)
> +acpi_get_gpiod_by_index(struct acpi_device *adev, const char *propname,
> +			int index, struct acpi_gpio_info *info)
>  {
>  	return ERR_PTR(-ENOSYS);
>  }
> -- 
> 1.9.3
> 
> 

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