drivers/dma/acpi-dma.c - kernel/msm-4.9 - Gitiles

 /*
  * ACPI helpers for DMA request / controller
  *
  * Based on of-dma.c
  *
  * Copyright (C) 2013, Intel Corporation
  * Authors: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
  *	    Mika Westerberg <mika.westerberg@linux.intel.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/ioport.h>
 #include <linux/acpi.h>
 #include <linux/acpi_dma.h>
 #include <linux/property.h>

 static LIST_HEAD(acpi_dma_list);
 static DEFINE_MUTEX(acpi_dma_lock);

 /**
  * acpi_dma_parse_resource_group - match device and parse resource group
  * @grp:	CSRT resource group
  * @adev:	ACPI device to match with
  * @adma:	struct acpi_dma of the given DMA controller
  *
  * In order to match a device from DSDT table to the corresponding CSRT device
  * we use MMIO address and IRQ.
  *
  * Return:
  * 1 on success, 0 when no information is available, or appropriate errno value
  * on error.
  */
 static int acpi_dma_parse_resource_group(const struct acpi_csrt_group *grp,
 		struct acpi_device *adev, struct acpi_dma *adma)
 {
 	const struct acpi_csrt_shared_info *si;
 	struct list_head resource_list;
 	struct resource_entry *rentry;
 	resource_size_t mem = 0, irq = 0;
 	int ret;

 	if (grp->shared_info_length != sizeof(struct acpi_csrt_shared_info))
 		return -ENODEV;

 	INIT_LIST_HEAD(&resource_list);
 	ret = acpi_dev_get_resources(adev, &resource_list, NULL, NULL);
 	if (ret <= 0)
 		return 0;

 	list_for_each_entry(rentry, &resource_list, node) {
 		if (resource_type(rentry->res) == IORESOURCE_MEM)
 			mem = rentry->res->start;
 		else if (resource_type(rentry->res) == IORESOURCE_IRQ)
 			irq = rentry->res->start;
 	}

 	acpi_dev_free_resource_list(&resource_list);

 	/* Consider initial zero values as resource not found */
 	if (mem == 0 && irq == 0)
 		return 0;

 	si = (const struct acpi_csrt_shared_info *)&grp[1];

 	/* Match device by MMIO and IRQ */
 	if (si->mmio_base_low != mem || si->gsi_interrupt != irq)
 		return 0;

 	dev_dbg(&adev->dev, "matches with %.4s%04X (rev %u)\n",
 		(char *)&grp->vendor_id, grp->device_id, grp->revision);

 	/* Check if the request line range is available */
 	if (si->base_request_line == 0 && si->num_handshake_signals == 0)
 		return 0;

 	adma->base_request_line = si->base_request_line;
 	adma->end_request_line = si->base_request_line +
 				 si->num_handshake_signals - 1;

 	dev_dbg(&adev->dev, "request line base: 0x%04x end: 0x%04x\n",
 		adma->base_request_line, adma->end_request_line);

 	return 1;
 }

 /**
  * acpi_dma_parse_csrt - parse CSRT to exctract additional DMA resources
  * @adev:	ACPI device to match with
  * @adma:	struct acpi_dma of the given DMA controller
  *
  * CSRT or Core System Resources Table is a proprietary ACPI table
  * introduced by Microsoft. This table can contain devices that are not in
  * the system DSDT table. In particular DMA controllers might be described
  * here.
  *
  * We are using this table to get the request line range of the specific DMA
  * controller to be used later.
  */
 static void acpi_dma_parse_csrt(struct acpi_device *adev, struct acpi_dma *adma)
 {
 	struct acpi_csrt_group *grp, *end;
 	struct acpi_table_csrt *csrt;
 	acpi_status status;
 	int ret;

 	status = acpi_get_table(ACPI_SIG_CSRT, 0,
 				(struct acpi_table_header **)&csrt);
 	if (ACPI_FAILURE(status)) {
 		if (status != AE_NOT_FOUND)
 			dev_warn(&adev->dev, "failed to get the CSRT table\n");
 		return;
 	}

 	grp = (struct acpi_csrt_group *)(csrt + 1);
 	end = (struct acpi_csrt_group *)((void *)csrt + csrt->header.length);

 	while (grp < end) {
 		ret = acpi_dma_parse_resource_group(grp, adev, adma);
 		if (ret < 0) {
 			dev_warn(&adev->dev,
 				 "error in parsing resource group\n");
 			return;
 		}

 		grp = (struct acpi_csrt_group *)((void *)grp + grp->length);
 	}
 }

 /**
  * acpi_dma_controller_register - Register a DMA controller to ACPI DMA helpers
  * @dev:		struct device of DMA controller
  * @acpi_dma_xlate:	translation function which converts a dma specifier
  *			into a dma_chan structure
  * @data		pointer to controller specific data to be used by
  *			translation function
  *
  * Allocated memory should be freed with appropriate acpi_dma_controller_free()
  * call.
  *
  * Return:
  * 0 on success or appropriate errno value on error.
  */
 int acpi_dma_controller_register(struct device *dev,
 		struct dma_chan *(*acpi_dma_xlate)
 		(struct acpi_dma_spec *, struct acpi_dma *),
 		void *data)
 {
 	struct acpi_device *adev;
 	struct acpi_dma	*adma;

 	if (!dev || !acpi_dma_xlate)
 		return -EINVAL;

 	/* Check if the device was enumerated by ACPI */
 	adev = ACPI_COMPANION(dev);
 	if (!adev)
 		return -EINVAL;

 	adma = kzalloc(sizeof(*adma), GFP_KERNEL);
 	if (!adma)
 		return -ENOMEM;

 	adma->dev = dev;
 	adma->acpi_dma_xlate = acpi_dma_xlate;
 	adma->data = data;

 	acpi_dma_parse_csrt(adev, adma);

 	/* Now queue acpi_dma controller structure in list */
 	mutex_lock(&acpi_dma_lock);
 	list_add_tail(&adma->dma_controllers, &acpi_dma_list);
 	mutex_unlock(&acpi_dma_lock);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(acpi_dma_controller_register);

 /**
  * acpi_dma_controller_free - Remove a DMA controller from ACPI DMA helpers list
  * @dev:	struct device of DMA controller
  *
  * Memory allocated by acpi_dma_controller_register() is freed here.
  *
  * Return:
  * 0 on success or appropriate errno value on error.
  */
 int acpi_dma_controller_free(struct device *dev)
 {
 	struct acpi_dma *adma;

 	if (!dev)
 		return -EINVAL;

 	mutex_lock(&acpi_dma_lock);

 	list_for_each_entry(adma, &acpi_dma_list, dma_controllers)
 		if (adma->dev == dev) {
 			list_del(&adma->dma_controllers);
 			mutex_unlock(&acpi_dma_lock);
 			kfree(adma);
 			return 0;
 		}

 	mutex_unlock(&acpi_dma_lock);
 	return -ENODEV;
 }
 EXPORT_SYMBOL_GPL(acpi_dma_controller_free);

 static void devm_acpi_dma_release(struct device *dev, void *res)
 {
 	acpi_dma_controller_free(dev);
 }

 /**
  * devm_acpi_dma_controller_register - resource managed acpi_dma_controller_register()
  * @dev:		device that is registering this DMA controller
  * @acpi_dma_xlate:	translation function
  * @data		pointer to controller specific data
  *
  * Managed acpi_dma_controller_register(). DMA controller registered by this
  * function are automatically freed on driver detach. See
  * acpi_dma_controller_register() for more information.
  *
  * Return:
  * 0 on success or appropriate errno value on error.
  */
 int devm_acpi_dma_controller_register(struct device *dev,
 		struct dma_chan *(*acpi_dma_xlate)
 		(struct acpi_dma_spec *, struct acpi_dma *),
 		void *data)
 {
 	void *res;
 	int ret;

 	res = devres_alloc(devm_acpi_dma_release, 0, GFP_KERNEL);
 	if (!res)
 		return -ENOMEM;

 	ret = acpi_dma_controller_register(dev, acpi_dma_xlate, data);
 	if (ret) {
 		devres_free(res);
 		return ret;
 	}
 	devres_add(dev, res);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(devm_acpi_dma_controller_register);

 /**
  * devm_acpi_dma_controller_free - resource managed acpi_dma_controller_free()
  *
  * Unregister a DMA controller registered with
  * devm_acpi_dma_controller_register(). Normally this function will not need to
  * be called and the resource management code will ensure that the resource is
  * freed.
  */
 void devm_acpi_dma_controller_free(struct device *dev)
 {
 	WARN_ON(devres_release(dev, devm_acpi_dma_release, NULL, NULL));
 }
 EXPORT_SYMBOL_GPL(devm_acpi_dma_controller_free);

 /**
  * acpi_dma_update_dma_spec - prepare dma specifier to pass to translation function
  * @adma:	struct acpi_dma of DMA controller
  * @dma_spec:	dma specifier to update
  *
  * Accordingly to ACPI 5.0 Specification Table 6-170 "Fixed DMA Resource
  * Descriptor":
  *	DMA Request Line bits is a platform-relative number uniquely
  *	identifying the request line assigned. Request line-to-Controller
  *	mapping is done in a controller-specific OS driver.
  * That's why we can safely adjust slave_id when the appropriate controller is
  * found.
  *
  * Return:
  * 0, if no information is avaiable, -1 on mismatch, and 1 otherwise.
  */
 static int acpi_dma_update_dma_spec(struct acpi_dma *adma,
 		struct acpi_dma_spec *dma_spec)
 {
 	/* Set link to the DMA controller device */
 	dma_spec->dev = adma->dev;

 	/* Check if the request line range is available */
 	if (adma->base_request_line == 0 && adma->end_request_line == 0)
 		return 0;

 	/* Check if slave_id falls to the range */
 	if (dma_spec->slave_id < adma->base_request_line ||
 	    dma_spec->slave_id > adma->end_request_line)
 		return -1;

 	/*
 	 * Here we adjust slave_id. It should be a relative number to the base
 	 * request line.
 	 */
 	dma_spec->slave_id -= adma->base_request_line;

 	return 1;
 }

 struct acpi_dma_parser_data {
 	struct acpi_dma_spec dma_spec;
 	size_t index;
 	size_t n;
 };

 /**
  * acpi_dma_parse_fixed_dma - Parse FixedDMA ACPI resources to a DMA specifier
  * @res:	struct acpi_resource to get FixedDMA resources from
  * @data:	pointer to a helper struct acpi_dma_parser_data
  */
 static int acpi_dma_parse_fixed_dma(struct acpi_resource *res, void *data)
 {
 	struct acpi_dma_parser_data *pdata = data;

 	if (res->type == ACPI_RESOURCE_TYPE_FIXED_DMA) {
 		struct acpi_resource_fixed_dma *dma = &res->data.fixed_dma;

 		if (pdata->n++ == pdata->index) {
 			pdata->dma_spec.chan_id = dma->channels;
 			pdata->dma_spec.slave_id = dma->request_lines;
 		}
 	}

 	/* Tell the ACPI core to skip this resource */
 	return 1;
 }

 /**
  * acpi_dma_request_slave_chan_by_index - Get the DMA slave channel
  * @dev:	struct device to get DMA request from
  * @index:	index of FixedDMA descriptor for @dev
  *
  * Return:
  * Pointer to appropriate dma channel on success or an error pointer.
  */
 struct dma_chan *acpi_dma_request_slave_chan_by_index(struct device *dev,
 		size_t index)
 {
 	struct acpi_dma_parser_data pdata;
 	struct acpi_dma_spec *dma_spec = &pdata.dma_spec;
 	struct list_head resource_list;
 	struct acpi_device *adev;
 	struct acpi_dma *adma;
 	struct dma_chan *chan = NULL;
 	int found;

 	/* Check if the device was enumerated by ACPI */
 	if (!dev)
 		return ERR_PTR(-ENODEV);

 	adev = ACPI_COMPANION(dev);
 	if (!adev)
 		return ERR_PTR(-ENODEV);

 	memset(&pdata, 0, sizeof(pdata));
 	pdata.index = index;

 	/* Initial values for the request line and channel */
 	dma_spec->chan_id = -1;
 	dma_spec->slave_id = -1;

 	INIT_LIST_HEAD(&resource_list);
 	acpi_dev_get_resources(adev, &resource_list,
 			acpi_dma_parse_fixed_dma, &pdata);
 	acpi_dev_free_resource_list(&resource_list);

 	if (dma_spec->slave_id < 0 || dma_spec->chan_id < 0)
 		return ERR_PTR(-ENODEV);

 	mutex_lock(&acpi_dma_lock);

 	list_for_each_entry(adma, &acpi_dma_list, dma_controllers) {
 		/*
 		 * We are not going to call translation function if slave_id
 		 * doesn't fall to the request range.
 		 */
 		found = acpi_dma_update_dma_spec(adma, dma_spec);
 		if (found < 0)
 			continue;
 		chan = adma->acpi_dma_xlate(dma_spec, adma);
 		/*
 		 * Try to get a channel only from the DMA controller that
 		 * matches the slave_id. See acpi_dma_update_dma_spec()
 		 * description for the details.
 		 */
 		if (found > 0 || chan)
 			break;
 	}

 	mutex_unlock(&acpi_dma_lock);
 	return chan ? chan : ERR_PTR(-EPROBE_DEFER);
 }
 EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_index);

 /**
  * acpi_dma_request_slave_chan_by_name - Get the DMA slave channel
  * @dev:	struct device to get DMA request from
  * @name:	represents corresponding FixedDMA descriptor for @dev
  *
  * In order to support both Device Tree and ACPI in a single driver we
  * translate the names "tx" and "rx" here based on the most common case where
  * the first FixedDMA descriptor is TX and second is RX.
  *
  * If the device has "dma-names" property the FixedDMA descriptor indices
  * are retrieved based on those. Otherwise the function falls back using
  * hardcoded indices.
  *
  * Return:
  * Pointer to appropriate dma channel on success or an error pointer.
  */
 struct dma_chan *acpi_dma_request_slave_chan_by_name(struct device *dev,
 		const char *name)
 {
 	int index;

 	index = device_property_match_string(dev, "dma-names", name);
 	if (index < 0) {
 		if (!strcmp(name, "tx"))
 			index = 0;
 		else if (!strcmp(name, "rx"))
 			index = 1;
 		else
 			return ERR_PTR(-ENODEV);
 	}

 	dev_dbg(dev, "found DMA channel \"%s\" at index %d\n", name, index);
 	return acpi_dma_request_slave_chan_by_index(dev, index);
 }
 EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_name);

 /**
  * acpi_dma_simple_xlate - Simple ACPI DMA engine translation helper
  * @dma_spec: pointer to ACPI DMA specifier
  * @adma: pointer to ACPI DMA controller data
  *
  * A simple translation function for ACPI based devices. Passes &struct
  * dma_spec to the DMA controller driver provided filter function.
  *
  * Return:
  * Pointer to the channel if found or %NULL otherwise.
  */
 struct dma_chan *acpi_dma_simple_xlate(struct acpi_dma_spec *dma_spec,
 		struct acpi_dma *adma)
 {
 	struct acpi_dma_filter_info *info = adma->data;

 	if (!info || !info->filter_fn)
 		return NULL;

 	return dma_request_channel(info->dma_cap, info->filter_fn, dma_spec);
 }
 EXPORT_SYMBOL_GPL(acpi_dma_simple_xlate);
	/*
	* ACPI helpers for DMA request / controller
	*
	* Based on of-dma.c
	*
	* Copyright (C) 2013, Intel Corporation
	* Authors: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
	* Mika Westerberg <mika.westerberg@linux.intel.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <linux/device.h>
	#include <linux/err.h>
	#include <linux/module.h>
	#include <linux/list.h>
	#include <linux/mutex.h>
	#include <linux/slab.h>
	#include <linux/ioport.h>
	#include <linux/acpi.h>
	#include <linux/acpi_dma.h>
	#include <linux/property.h>

	static LIST_HEAD(acpi_dma_list);
	static DEFINE_MUTEX(acpi_dma_lock);

	/**
	* acpi_dma_parse_resource_group - match device and parse resource group
	* @grp: CSRT resource group
	* @adev: ACPI device to match with
	* @adma: struct acpi_dma of the given DMA controller
	*
	* In order to match a device from DSDT table to the corresponding CSRT device
	* we use MMIO address and IRQ.
	*
	* Return:
	* 1 on success, 0 when no information is available, or appropriate errno value
	* on error.
	*/
	static int acpi_dma_parse_resource_group(const struct acpi_csrt_group *grp,
	struct acpi_device adev, struct acpi_dma adma)
	{
	const struct acpi_csrt_shared_info *si;
	struct list_head resource_list;
	struct resource_entry *rentry;
	resource_size_t mem = 0, irq = 0;
	int ret;

	if (grp->shared_info_length != sizeof(struct acpi_csrt_shared_info))
	return -ENODEV;

	INIT_LIST_HEAD(&resource_list);
	ret = acpi_dev_get_resources(adev, &resource_list, NULL, NULL);
	if (ret <= 0)
	return 0;

	list_for_each_entry(rentry, &resource_list, node) {
	if (resource_type(rentry->res) == IORESOURCE_MEM)
	mem = rentry->res->start;
	else if (resource_type(rentry->res) == IORESOURCE_IRQ)
	irq = rentry->res->start;
	}

	acpi_dev_free_resource_list(&resource_list);

	/* Consider initial zero values as resource not found */
	if (mem == 0 && irq == 0)
	return 0;

	si = (const struct acpi_csrt_shared_info *)&grp[1];

	/* Match device by MMIO and IRQ */
	if (si->mmio_base_low != mem \|\| si->gsi_interrupt != irq)
	return 0;

	dev_dbg(&adev->dev, "matches with %.4s%04X (rev %u)\n",
	(char *)&grp->vendor_id, grp->device_id, grp->revision);

	/* Check if the request line range is available */
	if (si->base_request_line == 0 && si->num_handshake_signals == 0)
	return 0;

	adma->base_request_line = si->base_request_line;
	adma->end_request_line = si->base_request_line +
	si->num_handshake_signals - 1;

	dev_dbg(&adev->dev, "request line base: 0x%04x end: 0x%04x\n",
	adma->base_request_line, adma->end_request_line);

	return 1;
	}

	/**
	* acpi_dma_parse_csrt - parse CSRT to exctract additional DMA resources
	* @adev: ACPI device to match with
	* @adma: struct acpi_dma of the given DMA controller
	*
	* CSRT or Core System Resources Table is a proprietary ACPI table
	* introduced by Microsoft. This table can contain devices that are not in
	* the system DSDT table. In particular DMA controllers might be described
	* here.
	*
	* We are using this table to get the request line range of the specific DMA
	* controller to be used later.
	*/
	static void acpi_dma_parse_csrt(struct acpi_device adev, struct acpi_dma adma)
	{
	struct acpi_csrt_group grp, end;
	struct acpi_table_csrt *csrt;
	acpi_status status;
	int ret;

	status = acpi_get_table(ACPI_SIG_CSRT, 0,
	(struct acpi_table_header **)&csrt);
	if (ACPI_FAILURE(status)) {
	if (status != AE_NOT_FOUND)
	dev_warn(&adev->dev, "failed to get the CSRT table\n");
	return;
	}

	grp = (struct acpi_csrt_group *)(csrt + 1);
	end = (struct acpi_csrt_group )((void )csrt + csrt->header.length);

	while (grp < end) {
	ret = acpi_dma_parse_resource_group(grp, adev, adma);
	if (ret < 0) {
	dev_warn(&adev->dev,
	"error in parsing resource group\n");
	return;
	}

	grp = (struct acpi_csrt_group )((void )grp + grp->length);
	}
	}

	/**
	* acpi_dma_controller_register - Register a DMA controller to ACPI DMA helpers
	* @dev: struct device of DMA controller
	* @acpi_dma_xlate: translation function which converts a dma specifier
	* into a dma_chan structure
	* @data pointer to controller specific data to be used by
	* translation function
	*
	* Allocated memory should be freed with appropriate acpi_dma_controller_free()
	* call.
	*
	* Return:
	* 0 on success or appropriate errno value on error.
	*/
	int acpi_dma_controller_register(struct device *dev,
	struct dma_chan (acpi_dma_xlate)
	(struct acpi_dma_spec , struct acpi_dma ),
	void *data)
	{
	struct acpi_device *adev;
	struct acpi_dma *adma;

	if (!dev \|\| !acpi_dma_xlate)
	return -EINVAL;

	/* Check if the device was enumerated by ACPI */
	adev = ACPI_COMPANION(dev);
	if (!adev)
	return -EINVAL;

	adma = kzalloc(sizeof(*adma), GFP_KERNEL);
	if (!adma)
	return -ENOMEM;

	adma->dev = dev;
	adma->acpi_dma_xlate = acpi_dma_xlate;
	adma->data = data;

	acpi_dma_parse_csrt(adev, adma);

	/* Now queue acpi_dma controller structure in list */
	mutex_lock(&acpi_dma_lock);
	list_add_tail(&adma->dma_controllers, &acpi_dma_list);
	mutex_unlock(&acpi_dma_lock);

	return 0;
	}
	EXPORT_SYMBOL_GPL(acpi_dma_controller_register);

	/**
	* acpi_dma_controller_free - Remove a DMA controller from ACPI DMA helpers list
	* @dev: struct device of DMA controller
	*
	* Memory allocated by acpi_dma_controller_register() is freed here.
	*
	* Return:
	* 0 on success or appropriate errno value on error.
	*/
	int acpi_dma_controller_free(struct device *dev)
	{
	struct acpi_dma *adma;

	if (!dev)
	return -EINVAL;

	mutex_lock(&acpi_dma_lock);

	list_for_each_entry(adma, &acpi_dma_list, dma_controllers)
	if (adma->dev == dev) {
	list_del(&adma->dma_controllers);
	mutex_unlock(&acpi_dma_lock);
	kfree(adma);
	return 0;
	}

	mutex_unlock(&acpi_dma_lock);
	return -ENODEV;
	}
	EXPORT_SYMBOL_GPL(acpi_dma_controller_free);

	static void devm_acpi_dma_release(struct device dev, void res)
	{
	acpi_dma_controller_free(dev);
	}

	/**
	* devm_acpi_dma_controller_register - resource managed acpi_dma_controller_register()
	* @dev: device that is registering this DMA controller
	* @acpi_dma_xlate: translation function
	* @data pointer to controller specific data
	*
	* Managed acpi_dma_controller_register(). DMA controller registered by this
	* function are automatically freed on driver detach. See
	* acpi_dma_controller_register() for more information.
	*
	* Return:
	* 0 on success or appropriate errno value on error.
	*/
	int devm_acpi_dma_controller_register(struct device *dev,
	struct dma_chan (acpi_dma_xlate)
	(struct acpi_dma_spec , struct acpi_dma ),
	void *data)
	{
	void *res;
	int ret;

	res = devres_alloc(devm_acpi_dma_release, 0, GFP_KERNEL);
	if (!res)
	return -ENOMEM;

	ret = acpi_dma_controller_register(dev, acpi_dma_xlate, data);
	if (ret) {
	devres_free(res);
	return ret;
	}
	devres_add(dev, res);
	return 0;
	}
	EXPORT_SYMBOL_GPL(devm_acpi_dma_controller_register);

	/**
	* devm_acpi_dma_controller_free - resource managed acpi_dma_controller_free()
	*
	* Unregister a DMA controller registered with
	* devm_acpi_dma_controller_register(). Normally this function will not need to
	* be called and the resource management code will ensure that the resource is
	* freed.
	*/
	void devm_acpi_dma_controller_free(struct device *dev)
	{
	WARN_ON(devres_release(dev, devm_acpi_dma_release, NULL, NULL));
	}
	EXPORT_SYMBOL_GPL(devm_acpi_dma_controller_free);

	/**
	* acpi_dma_update_dma_spec - prepare dma specifier to pass to translation function
	* @adma: struct acpi_dma of DMA controller
	* @dma_spec: dma specifier to update
	*
	* Accordingly to ACPI 5.0 Specification Table 6-170 "Fixed DMA Resource
	* Descriptor":
	* DMA Request Line bits is a platform-relative number uniquely
	* identifying the request line assigned. Request line-to-Controller
	* mapping is done in a controller-specific OS driver.
	* That's why we can safely adjust slave_id when the appropriate controller is
	* found.
	*
	* Return:
	* 0, if no information is avaiable, -1 on mismatch, and 1 otherwise.
	*/
	static int acpi_dma_update_dma_spec(struct acpi_dma *adma,
	struct acpi_dma_spec *dma_spec)
	{
	/* Set link to the DMA controller device */
	dma_spec->dev = adma->dev;

	/* Check if the request line range is available */
	if (adma->base_request_line == 0 && adma->end_request_line == 0)
	return 0;

	/* Check if slave_id falls to the range */
	if (dma_spec->slave_id < adma->base_request_line \|\|
	dma_spec->slave_id > adma->end_request_line)
	return -1;

	/*
	* Here we adjust slave_id. It should be a relative number to the base
	* request line.
	*/
	dma_spec->slave_id -= adma->base_request_line;

	return 1;
	}

	struct acpi_dma_parser_data {
	struct acpi_dma_spec dma_spec;
	size_t index;
	size_t n;
	};

	/**
	* acpi_dma_parse_fixed_dma - Parse FixedDMA ACPI resources to a DMA specifier
	* @res: struct acpi_resource to get FixedDMA resources from
	* @data: pointer to a helper struct acpi_dma_parser_data
	*/
	static int acpi_dma_parse_fixed_dma(struct acpi_resource res, void data)
	{
	struct acpi_dma_parser_data *pdata = data;

	if (res->type == ACPI_RESOURCE_TYPE_FIXED_DMA) {
	struct acpi_resource_fixed_dma *dma = &res->data.fixed_dma;

	if (pdata->n++ == pdata->index) {
	pdata->dma_spec.chan_id = dma->channels;
	pdata->dma_spec.slave_id = dma->request_lines;
	}
	}

	/* Tell the ACPI core to skip this resource */
	return 1;
	}

	/**
	* acpi_dma_request_slave_chan_by_index - Get the DMA slave channel
	* @dev: struct device to get DMA request from
	* @index: index of FixedDMA descriptor for @dev
	*
	* Return:
	* Pointer to appropriate dma channel on success or an error pointer.
	*/
	struct dma_chan acpi_dma_request_slave_chan_by_index(struct device dev,
	size_t index)
	{
	struct acpi_dma_parser_data pdata;
	struct acpi_dma_spec *dma_spec = &pdata.dma_spec;
	struct list_head resource_list;
	struct acpi_device *adev;
	struct acpi_dma *adma;
	struct dma_chan *chan = NULL;
	int found;

	/* Check if the device was enumerated by ACPI */
	if (!dev)
	return ERR_PTR(-ENODEV);

	adev = ACPI_COMPANION(dev);
	if (!adev)
	return ERR_PTR(-ENODEV);

	memset(&pdata, 0, sizeof(pdata));
	pdata.index = index;

	/* Initial values for the request line and channel */
	dma_spec->chan_id = -1;
	dma_spec->slave_id = -1;

	INIT_LIST_HEAD(&resource_list);
	acpi_dev_get_resources(adev, &resource_list,
	acpi_dma_parse_fixed_dma, &pdata);
	acpi_dev_free_resource_list(&resource_list);

	if (dma_spec->slave_id < 0 \|\| dma_spec->chan_id < 0)
	return ERR_PTR(-ENODEV);

	mutex_lock(&acpi_dma_lock);

	list_for_each_entry(adma, &acpi_dma_list, dma_controllers) {
	/*
	* We are not going to call translation function if slave_id
	* doesn't fall to the request range.
	*/
	found = acpi_dma_update_dma_spec(adma, dma_spec);
	if (found < 0)
	continue;
	chan = adma->acpi_dma_xlate(dma_spec, adma);
	/*
	* Try to get a channel only from the DMA controller that
	* matches the slave_id. See acpi_dma_update_dma_spec()
	* description for the details.
	*/
	if (found > 0 \|\| chan)
	break;
	}

	mutex_unlock(&acpi_dma_lock);
	return chan ? chan : ERR_PTR(-EPROBE_DEFER);
	}
	EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_index);

	/**
	* acpi_dma_request_slave_chan_by_name - Get the DMA slave channel
	* @dev: struct device to get DMA request from
	* @name: represents corresponding FixedDMA descriptor for @dev
	*
	* In order to support both Device Tree and ACPI in a single driver we
	* translate the names "tx" and "rx" here based on the most common case where
	* the first FixedDMA descriptor is TX and second is RX.
	*
	* If the device has "dma-names" property the FixedDMA descriptor indices
	* are retrieved based on those. Otherwise the function falls back using
	* hardcoded indices.
	*
	* Return:
	* Pointer to appropriate dma channel on success or an error pointer.
	*/
	struct dma_chan acpi_dma_request_slave_chan_by_name(struct device dev,
	const char *name)
	{
	int index;

	index = device_property_match_string(dev, "dma-names", name);
	if (index < 0) {
	if (!strcmp(name, "tx"))
	index = 0;
	else if (!strcmp(name, "rx"))
	index = 1;
	else
	return ERR_PTR(-ENODEV);
	}

	dev_dbg(dev, "found DMA channel \"%s\" at index %d\n", name, index);
	return acpi_dma_request_slave_chan_by_index(dev, index);
	}
	EXPORT_SYMBOL_GPL(acpi_dma_request_slave_chan_by_name);

	/**
	* acpi_dma_simple_xlate - Simple ACPI DMA engine translation helper
	* @dma_spec: pointer to ACPI DMA specifier
	* @adma: pointer to ACPI DMA controller data
	*
	* A simple translation function for ACPI based devices. Passes &struct
	* dma_spec to the DMA controller driver provided filter function.
	*
	* Return:
	* Pointer to the channel if found or %NULL otherwise.
	*/
	struct dma_chan acpi_dma_simple_xlate(struct acpi_dma_spec dma_spec,
	struct acpi_dma *adma)
	{
	struct acpi_dma_filter_info *info = adma->data;

	if (!info \|\| !info->filter_fn)
	return NULL;

	return dma_request_channel(info->dma_cap, info->filter_fn, dma_spec);
	}
	EXPORT_SYMBOL_GPL(acpi_dma_simple_xlate);