drivers/pci/ats.c - linux-imx - Git at Google

 /*
  * drivers/pci/ats.c
  *
  * Copyright (C) 2009 Intel Corporation, Yu Zhao <yu.zhao@intel.com>
  * Copyright (C) 2011 Advanced Micro Devices,
  *
  * PCI Express I/O Virtualization (IOV) support.
  *   Address Translation Service 1.0
  *   Page Request Interface added by Joerg Roedel <joerg.roedel@amd.com>
  *   PASID support added by Joerg Roedel <joerg.roedel@amd.com>
  */

 #include <linux/export.h>
 #include <linux/pci-ats.h>
 #include <linux/pci.h>
 #include <linux/slab.h>

 #include "pci.h"

 void pci_ats_init(struct pci_dev *dev)
 {
 	int pos;

 	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ATS);
 	if (!pos)
 		return;

 	dev->ats_cap = pos;
 }

 /**
  * pci_enable_ats - enable the ATS capability
  * @dev: the PCI device
  * @ps: the IOMMU page shift
  *
  * Returns 0 on success, or negative on failure.
  */
 int pci_enable_ats(struct pci_dev *dev, int ps)
 {
 	u16 ctrl;
 	struct pci_dev *pdev;

 	if (!dev->ats_cap)
 		return -EINVAL;

 	if (WARN_ON(dev->ats_enabled))
 		return -EBUSY;

 	if (ps < PCI_ATS_MIN_STU)
 		return -EINVAL;

 	/*
 	 * Note that enabling ATS on a VF fails unless it's already enabled
 	 * with the same STU on the PF.
 	 */
 	ctrl = PCI_ATS_CTRL_ENABLE;
 	if (dev->is_virtfn) {
 		pdev = pci_physfn(dev);
 		if (pdev->ats_stu != ps)
 			return -EINVAL;

 		atomic_inc(&pdev->ats_ref_cnt);  /* count enabled VFs */
 	} else {
 		dev->ats_stu = ps;
 		ctrl |= PCI_ATS_CTRL_STU(dev->ats_stu - PCI_ATS_MIN_STU);
 	}
 	pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);

 	dev->ats_enabled = 1;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_enable_ats);

 /**
  * pci_disable_ats - disable the ATS capability
  * @dev: the PCI device
  */
 void pci_disable_ats(struct pci_dev *dev)
 {
 	struct pci_dev *pdev;
 	u16 ctrl;

 	if (WARN_ON(!dev->ats_enabled))
 		return;

 	if (atomic_read(&dev->ats_ref_cnt))
 		return;		/* VFs still enabled */

 	if (dev->is_virtfn) {
 		pdev = pci_physfn(dev);
 		atomic_dec(&pdev->ats_ref_cnt);
 	}

 	pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, &ctrl);
 	ctrl &= ~PCI_ATS_CTRL_ENABLE;
 	pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);

 	dev->ats_enabled = 0;
 }
 EXPORT_SYMBOL_GPL(pci_disable_ats);

 void pci_restore_ats_state(struct pci_dev *dev)
 {
 	u16 ctrl;

 	if (!dev->ats_enabled)
 		return;

 	ctrl = PCI_ATS_CTRL_ENABLE;
 	if (!dev->is_virtfn)
 		ctrl |= PCI_ATS_CTRL_STU(dev->ats_stu - PCI_ATS_MIN_STU);
 	pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);
 }
 EXPORT_SYMBOL_GPL(pci_restore_ats_state);

 /**
  * pci_ats_queue_depth - query the ATS Invalidate Queue Depth
  * @dev: the PCI device
  *
  * Returns the queue depth on success, or negative on failure.
  *
  * The ATS spec uses 0 in the Invalidate Queue Depth field to
  * indicate that the function can accept 32 Invalidate Request.
  * But here we use the `real' values (i.e. 1~32) for the Queue
  * Depth; and 0 indicates the function shares the Queue with
  * other functions (doesn't exclusively own a Queue).
  */
 int pci_ats_queue_depth(struct pci_dev *dev)
 {
 	u16 cap;

 	if (!dev->ats_cap)
 		return -EINVAL;

 	if (dev->is_virtfn)
 		return 0;

 	pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CAP, &cap);
 	return PCI_ATS_CAP_QDEP(cap) ? PCI_ATS_CAP_QDEP(cap) : PCI_ATS_MAX_QDEP;
 }
 EXPORT_SYMBOL_GPL(pci_ats_queue_depth);

 #ifdef CONFIG_PCI_PRI
 /**
  * pci_enable_pri - Enable PRI capability
  * @ pdev: PCI device structure
  *
  * Returns 0 on success, negative value on error
  */
 int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
 {
 	u16 control, status;
 	u32 max_requests;
 	int pos;

 	if (WARN_ON(pdev->pri_enabled))
 		return -EBUSY;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
 	if (!pos)
 		return -EINVAL;

 	pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
 	if (!(status & PCI_PRI_STATUS_STOPPED))
 		return -EBUSY;

 	pci_read_config_dword(pdev, pos + PCI_PRI_MAX_REQ, &max_requests);
 	reqs = min(max_requests, reqs);
 	pdev->pri_reqs_alloc = reqs;
 	pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);

 	control = PCI_PRI_CTRL_ENABLE;
 	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);

 	pdev->pri_enabled = 1;

 	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_enable_pri);

 /**
  * pci_disable_pri - Disable PRI capability
  * @pdev: PCI device structure
  *
  * Only clears the enabled-bit, regardless of its former value
  */
 void pci_disable_pri(struct pci_dev *pdev)
 {
 	u16 control;
 	int pos;

 	if (WARN_ON(!pdev->pri_enabled))
 		return;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
 	if (!pos)
 		return;

 	pci_read_config_word(pdev, pos + PCI_PRI_CTRL, &control);
 	control &= ~PCI_PRI_CTRL_ENABLE;
 	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);

 	pdev->pri_enabled = 0;
 }
 EXPORT_SYMBOL_GPL(pci_disable_pri);

 /**
  * pci_restore_pri_state - Restore PRI
  * @pdev: PCI device structure
  */
 void pci_restore_pri_state(struct pci_dev *pdev)
 {
 	u16 control = PCI_PRI_CTRL_ENABLE;
 	u32 reqs = pdev->pri_reqs_alloc;
 	int pos;

 	if (!pdev->pri_enabled)
 		return;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
 	if (!pos)
 		return;

 	pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);
 	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
 }
 EXPORT_SYMBOL_GPL(pci_restore_pri_state);

 /**
  * pci_reset_pri - Resets device's PRI state
  * @pdev: PCI device structure
  *
  * The PRI capability must be disabled before this function is called.
  * Returns 0 on success, negative value on error.
  */
 int pci_reset_pri(struct pci_dev *pdev)
 {
 	u16 control;
 	int pos;

 	if (WARN_ON(pdev->pri_enabled))
 		return -EBUSY;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
 	if (!pos)
 		return -EINVAL;

 	control = PCI_PRI_CTRL_RESET;
 	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_reset_pri);
 #endif /* CONFIG_PCI_PRI */

 #ifdef CONFIG_PCI_PASID
 /**
  * pci_enable_pasid - Enable the PASID capability
  * @pdev: PCI device structure
  * @features: Features to enable
  *
  * Returns 0 on success, negative value on error. This function checks
  * whether the features are actually supported by the device and returns
  * an error if not.
  */
 int pci_enable_pasid(struct pci_dev *pdev, int features)
 {
 	u16 control, supported;
 	int pos;

 	if (WARN_ON(pdev->pasid_enabled))
 		return -EBUSY;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
 	if (!pos)
 		return -EINVAL;

 	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);
 	supported &= PCI_PASID_CAP_EXEC | PCI_PASID_CAP_PRIV;

 	/* User wants to enable anything unsupported? */
 	if ((supported & features) != features)
 		return -EINVAL;

 	control = PCI_PASID_CTRL_ENABLE | features;
 	pdev->pasid_features = features;

 	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);

 	pdev->pasid_enabled = 1;

 	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_enable_pasid);

 /**
  * pci_disable_pasid - Disable the PASID capability
  * @pdev: PCI device structure
  */
 void pci_disable_pasid(struct pci_dev *pdev)
 {
 	u16 control = 0;
 	int pos;

 	if (WARN_ON(!pdev->pasid_enabled))
 		return;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
 	if (!pos)
 		return;

 	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);

 	pdev->pasid_enabled = 0;
 }
 EXPORT_SYMBOL_GPL(pci_disable_pasid);

 /**
  * pci_restore_pasid_state - Restore PASID capabilities
  * @pdev: PCI device structure
  */
 void pci_restore_pasid_state(struct pci_dev *pdev)
 {
 	u16 control;
 	int pos;

 	if (!pdev->pasid_enabled)
 		return;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
 	if (!pos)
 		return;

 	control = PCI_PASID_CTRL_ENABLE | pdev->pasid_features;
 	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);
 }
 EXPORT_SYMBOL_GPL(pci_restore_pasid_state);

 /**
  * pci_pasid_features - Check which PASID features are supported
  * @pdev: PCI device structure
  *
  * Returns a negative value when no PASI capability is present.
  * Otherwise is returns a bitmask with supported features. Current
  * features reported are:
  * PCI_PASID_CAP_EXEC - Execute permission supported
  * PCI_PASID_CAP_PRIV - Privileged mode supported
  */
 int pci_pasid_features(struct pci_dev *pdev)
 {
 	u16 supported;
 	int pos;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
 	if (!pos)
 		return -EINVAL;

 	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);

 	supported &= PCI_PASID_CAP_EXEC | PCI_PASID_CAP_PRIV;

 	return supported;
 }
 EXPORT_SYMBOL_GPL(pci_pasid_features);

 #define PASID_NUMBER_SHIFT	8
 #define PASID_NUMBER_MASK	(0x1f << PASID_NUMBER_SHIFT)
 /**
  * pci_max_pasid - Get maximum number of PASIDs supported by device
  * @pdev: PCI device structure
  *
  * Returns negative value when PASID capability is not present.
  * Otherwise it returns the numer of supported PASIDs.
  */
 int pci_max_pasids(struct pci_dev *pdev)
 {
 	u16 supported;
 	int pos;

 	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
 	if (!pos)
 		return -EINVAL;

 	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);

 	supported = (supported & PASID_NUMBER_MASK) >> PASID_NUMBER_SHIFT;

 	return (1 << supported);
 }
 EXPORT_SYMBOL_GPL(pci_max_pasids);
 #endif /* CONFIG_PCI_PASID */
	/*
	* drivers/pci/ats.c
	*
	* Copyright (C) 2009 Intel Corporation, Yu Zhao <yu.zhao@intel.com>
	* Copyright (C) 2011 Advanced Micro Devices,
	*
	* PCI Express I/O Virtualization (IOV) support.
	* Address Translation Service 1.0
	* Page Request Interface added by Joerg Roedel <joerg.roedel@amd.com>
	* PASID support added by Joerg Roedel <joerg.roedel@amd.com>
	*/

	#include <linux/export.h>
	#include <linux/pci-ats.h>
	#include <linux/pci.h>
	#include <linux/slab.h>

	#include "pci.h"

	void pci_ats_init(struct pci_dev *dev)
	{
	int pos;

	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ATS);
	if (!pos)
	return;

	dev->ats_cap = pos;
	}

	/**
	* pci_enable_ats - enable the ATS capability
	* @dev: the PCI device
	* @ps: the IOMMU page shift
	*
	* Returns 0 on success, or negative on failure.
	*/
	int pci_enable_ats(struct pci_dev *dev, int ps)
	{
	u16 ctrl;
	struct pci_dev *pdev;

	if (!dev->ats_cap)
	return -EINVAL;

	if (WARN_ON(dev->ats_enabled))
	return -EBUSY;

	if (ps < PCI_ATS_MIN_STU)
	return -EINVAL;

	/*
	* Note that enabling ATS on a VF fails unless it's already enabled
	* with the same STU on the PF.
	*/
	ctrl = PCI_ATS_CTRL_ENABLE;
	if (dev->is_virtfn) {
	pdev = pci_physfn(dev);
	if (pdev->ats_stu != ps)
	return -EINVAL;

	atomic_inc(&pdev->ats_ref_cnt); /* count enabled VFs */
	} else {
	dev->ats_stu = ps;
	ctrl \|= PCI_ATS_CTRL_STU(dev->ats_stu - PCI_ATS_MIN_STU);
	}
	pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);

	dev->ats_enabled = 1;
	return 0;
	}
	EXPORT_SYMBOL_GPL(pci_enable_ats);

	/**
	* pci_disable_ats - disable the ATS capability
	* @dev: the PCI device
	*/
	void pci_disable_ats(struct pci_dev *dev)
	{
	struct pci_dev *pdev;
	u16 ctrl;

	if (WARN_ON(!dev->ats_enabled))
	return;

	if (atomic_read(&dev->ats_ref_cnt))
	return; /* VFs still enabled */

	if (dev->is_virtfn) {
	pdev = pci_physfn(dev);
	atomic_dec(&pdev->ats_ref_cnt);
	}

	pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, &ctrl);
	ctrl &= ~PCI_ATS_CTRL_ENABLE;
	pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);

	dev->ats_enabled = 0;
	}
	EXPORT_SYMBOL_GPL(pci_disable_ats);

	void pci_restore_ats_state(struct pci_dev *dev)
	{
	u16 ctrl;

	if (!dev->ats_enabled)
	return;

	ctrl = PCI_ATS_CTRL_ENABLE;
	if (!dev->is_virtfn)
	ctrl \|= PCI_ATS_CTRL_STU(dev->ats_stu - PCI_ATS_MIN_STU);
	pci_write_config_word(dev, dev->ats_cap + PCI_ATS_CTRL, ctrl);
	}
	EXPORT_SYMBOL_GPL(pci_restore_ats_state);

	/**
	* pci_ats_queue_depth - query the ATS Invalidate Queue Depth
	* @dev: the PCI device
	*
	* Returns the queue depth on success, or negative on failure.
	*
	* The ATS spec uses 0 in the Invalidate Queue Depth field to
	* indicate that the function can accept 32 Invalidate Request.
	* But here we use the `real' values (i.e. 1~32) for the Queue
	* Depth; and 0 indicates the function shares the Queue with
	* other functions (doesn't exclusively own a Queue).
	*/
	int pci_ats_queue_depth(struct pci_dev *dev)
	{
	u16 cap;

	if (!dev->ats_cap)
	return -EINVAL;

	if (dev->is_virtfn)
	return 0;

	pci_read_config_word(dev, dev->ats_cap + PCI_ATS_CAP, &cap);
	return PCI_ATS_CAP_QDEP(cap) ? PCI_ATS_CAP_QDEP(cap) : PCI_ATS_MAX_QDEP;
	}
	EXPORT_SYMBOL_GPL(pci_ats_queue_depth);

	#ifdef CONFIG_PCI_PRI
	/**
	* pci_enable_pri - Enable PRI capability
	* @ pdev: PCI device structure
	*
	* Returns 0 on success, negative value on error
	*/
	int pci_enable_pri(struct pci_dev *pdev, u32 reqs)
	{
	u16 control, status;
	u32 max_requests;
	int pos;

	if (WARN_ON(pdev->pri_enabled))
	return -EBUSY;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
	if (!pos)
	return -EINVAL;

	pci_read_config_word(pdev, pos + PCI_PRI_STATUS, &status);
	if (!(status & PCI_PRI_STATUS_STOPPED))
	return -EBUSY;

	pci_read_config_dword(pdev, pos + PCI_PRI_MAX_REQ, &max_requests);
	reqs = min(max_requests, reqs);
	pdev->pri_reqs_alloc = reqs;
	pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);

	control = PCI_PRI_CTRL_ENABLE;
	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);

	pdev->pri_enabled = 1;

	return 0;
	}
	EXPORT_SYMBOL_GPL(pci_enable_pri);

	/**
	* pci_disable_pri - Disable PRI capability
	* @pdev: PCI device structure
	*
	* Only clears the enabled-bit, regardless of its former value
	*/
	void pci_disable_pri(struct pci_dev *pdev)
	{
	u16 control;
	int pos;

	if (WARN_ON(!pdev->pri_enabled))
	return;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
	if (!pos)
	return;

	pci_read_config_word(pdev, pos + PCI_PRI_CTRL, &control);
	control &= ~PCI_PRI_CTRL_ENABLE;
	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);

	pdev->pri_enabled = 0;
	}
	EXPORT_SYMBOL_GPL(pci_disable_pri);

	/**
	* pci_restore_pri_state - Restore PRI
	* @pdev: PCI device structure
	*/
	void pci_restore_pri_state(struct pci_dev *pdev)
	{
	u16 control = PCI_PRI_CTRL_ENABLE;
	u32 reqs = pdev->pri_reqs_alloc;
	int pos;

	if (!pdev->pri_enabled)
	return;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
	if (!pos)
	return;

	pci_write_config_dword(pdev, pos + PCI_PRI_ALLOC_REQ, reqs);
	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);
	}
	EXPORT_SYMBOL_GPL(pci_restore_pri_state);

	/**
	* pci_reset_pri - Resets device's PRI state
	* @pdev: PCI device structure
	*
	* The PRI capability must be disabled before this function is called.
	* Returns 0 on success, negative value on error.
	*/
	int pci_reset_pri(struct pci_dev *pdev)
	{
	u16 control;
	int pos;

	if (WARN_ON(pdev->pri_enabled))
	return -EBUSY;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PRI);
	if (!pos)
	return -EINVAL;

	control = PCI_PRI_CTRL_RESET;
	pci_write_config_word(pdev, pos + PCI_PRI_CTRL, control);

	return 0;
	}
	EXPORT_SYMBOL_GPL(pci_reset_pri);
	#endif /* CONFIG_PCI_PRI */

	#ifdef CONFIG_PCI_PASID
	/**
	* pci_enable_pasid - Enable the PASID capability
	* @pdev: PCI device structure
	* @features: Features to enable
	*
	* Returns 0 on success, negative value on error. This function checks
	* whether the features are actually supported by the device and returns
	* an error if not.
	*/
	int pci_enable_pasid(struct pci_dev *pdev, int features)
	{
	u16 control, supported;
	int pos;

	if (WARN_ON(pdev->pasid_enabled))
	return -EBUSY;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
	if (!pos)
	return -EINVAL;

	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);
	supported &= PCI_PASID_CAP_EXEC \| PCI_PASID_CAP_PRIV;

	/* User wants to enable anything unsupported? */
	if ((supported & features) != features)
	return -EINVAL;

	control = PCI_PASID_CTRL_ENABLE \| features;
	pdev->pasid_features = features;

	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);

	pdev->pasid_enabled = 1;

	return 0;
	}
	EXPORT_SYMBOL_GPL(pci_enable_pasid);

	/**
	* pci_disable_pasid - Disable the PASID capability
	* @pdev: PCI device structure
	*/
	void pci_disable_pasid(struct pci_dev *pdev)
	{
	u16 control = 0;
	int pos;

	if (WARN_ON(!pdev->pasid_enabled))
	return;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
	if (!pos)
	return;

	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);

	pdev->pasid_enabled = 0;
	}
	EXPORT_SYMBOL_GPL(pci_disable_pasid);

	/**
	* pci_restore_pasid_state - Restore PASID capabilities
	* @pdev: PCI device structure
	*/
	void pci_restore_pasid_state(struct pci_dev *pdev)
	{
	u16 control;
	int pos;

	if (!pdev->pasid_enabled)
	return;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
	if (!pos)
	return;

	control = PCI_PASID_CTRL_ENABLE \| pdev->pasid_features;
	pci_write_config_word(pdev, pos + PCI_PASID_CTRL, control);
	}
	EXPORT_SYMBOL_GPL(pci_restore_pasid_state);

	/**
	* pci_pasid_features - Check which PASID features are supported
	* @pdev: PCI device structure
	*
	* Returns a negative value when no PASI capability is present.
	* Otherwise is returns a bitmask with supported features. Current
	* features reported are:
	* PCI_PASID_CAP_EXEC - Execute permission supported
	* PCI_PASID_CAP_PRIV - Privileged mode supported
	*/
	int pci_pasid_features(struct pci_dev *pdev)
	{
	u16 supported;
	int pos;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
	if (!pos)
	return -EINVAL;

	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);

	supported &= PCI_PASID_CAP_EXEC \| PCI_PASID_CAP_PRIV;

	return supported;
	}
	EXPORT_SYMBOL_GPL(pci_pasid_features);

	#define PASID_NUMBER_SHIFT 8
	#define PASID_NUMBER_MASK (0x1f << PASID_NUMBER_SHIFT)
	/**
	* pci_max_pasid - Get maximum number of PASIDs supported by device
	* @pdev: PCI device structure
	*
	* Returns negative value when PASID capability is not present.
	* Otherwise it returns the numer of supported PASIDs.
	*/
	int pci_max_pasids(struct pci_dev *pdev)
	{
	u16 supported;
	int pos;

	pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_PASID);
	if (!pos)
	return -EINVAL;

	pci_read_config_word(pdev, pos + PCI_PASID_CAP, &supported);

	supported = (supported & PASID_NUMBER_MASK) >> PASID_NUMBER_SHIFT;

	return (1 << supported);
	}
	EXPORT_SYMBOL_GPL(pci_max_pasids);
	#endif /* CONFIG_PCI_PASID */