pci/msi/msi.c

// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Message Signaled Interrupt (MSI)
 *
 * Copyright (C) 2003-2004 Intel
 * Copyright (C) Tom Long Nguyen (tom.l.nguyen@intel.com)
 * Copyright (C) 2016 Christoph Hellwig.
 */
#include <linux/bitfield.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>

#include "../pci.h"
#include "msi.h"

int pci_msi_enable = 1;

/**
 * pci_msi_supported - check whether MSI may be enabled on a device
 * @dev: pointer to the pci_dev data structure of MSI device function
 * @nvec: how many MSIs have been requested?
 *
 * Look at global flags, the device itself, and its parent buses
 * to determine if MSI/-X are supported for the device. If MSI/-X is
 * supported return 1, else return 0.
 **/
static int pci_msi_supported(struct pci_dev *dev, int nvec)
{
	struct pci_bus *bus;

	/* MSI must be globally enabled and supported by the device */
	if (!pci_msi_enable)
		return 0;

	if (!dev || dev->no_msi)
		return 0;

	/*
	 * You can't ask to have 0 or less MSIs configured.
	 *  a) it's stupid ..
	 *  b) the list manipulation code assumes nvec >= 1.
	 */
	if (nvec < 1)
		return 0;

	/*
	 * Any bridge which does NOT route MSI transactions from its
	 * secondary bus to its primary bus must set NO_MSI flag on
	 * the secondary pci_bus.
	 *
	 * The NO_MSI flag can either be set directly by:
	 * - arch-specific PCI host bus controller drivers (deprecated)
	 * - quirks for specific PCI bridges
	 *
	 * or indirectly by platform-specific PCI host bridge drivers by
	 * advertising the 'msi_domain' property, which results in
	 * the NO_MSI flag when no MSI domain is found for this bridge
	 * at probe time.
	 */
	for (bus = dev->bus; bus; bus = bus->parent)
		if (bus->bus_flags & PCI_BUS_FLAGS_NO_MSI)
			return 0;

	return 1;
}

static void pcim_msi_release(void *pcidev)
{
	struct pci_dev *dev = pcidev;

	dev->is_msi_managed = false;
	pci_free_irq_vectors(dev);
}

/*
 * Needs to be separate from pcim_release to prevent an ordering problem
 * vs. msi_device_data_release() in the MSI core code.
 */
static int pcim_setup_msi_release(struct pci_dev *dev)
{
	int ret;

	if (!pci_is_managed(dev) || dev->is_msi_managed)
		return 0;

	ret = devm_add_action(&dev->dev, pcim_msi_release, dev);
	if (ret)
		return ret;

	dev->is_msi_managed = true;
	return 0;
}

/*
 * Ordering vs. devres: msi device data has to be installed first so that
 * pcim_msi_release() is invoked before it on device release.
 */
static int pci_setup_msi_context(struct pci_dev *dev)
{
	int ret = msi_setup_device_data(&dev->dev);

	if (ret)
		return ret;

	return pcim_setup_msi_release(dev);
}

/*
 * Helper functions for mask/unmask and MSI message handling
 */

void pci_msi_update_mask(struct msi_desc *desc, u32 clear, u32 set)
{
	raw_spinlock_t *lock = &to_pci_dev(desc->dev)->msi_lock;
	unsigned long flags;

	if (!desc->pci.msi_attrib.can_mask)
		return;

	raw_spin_lock_irqsave(lock, flags);
	desc->pci.msi_mask &= ~clear;
	desc->pci.msi_mask |= set;
	pci_write_config_dword(msi_desc_to_pci_dev(desc), desc->pci.mask_pos,
			       desc->pci.msi_mask);
	raw_spin_unlock_irqrestore(lock, flags);
}

/**
 * pci_msi_mask_irq - Generic IRQ chip callback to mask PCI/MSI interrupts
 * @data:	pointer to irqdata associated to that interrupt
 */
void pci_msi_mask_irq(struct irq_data *data)
{
	struct msi_desc *desc = irq_data_get_msi_desc(data);

	__pci_msi_mask_desc(desc, BIT(data->irq - desc->irq));
}
EXPORT_SYMBOL_GPL(pci_msi_mask_irq);

/**
 * pci_msi_unmask_irq - Generic IRQ chip callback to unmask PCI/MSI interrupts
 * @data:	pointer to irqdata associated to that interrupt
 */
void pci_msi_unmask_irq(struct irq_data *data)
{
	struct msi_desc *desc = irq_data_get_msi_desc(data);

	__pci_msi_unmask_desc(desc, BIT(data->irq - desc->irq));
}
EXPORT_SYMBOL_GPL(pci_msi_unmask_irq);

void __pci_read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
{
	struct pci_dev *dev = msi_desc_to_pci_dev(entry);

	BUG_ON(dev->current_state != PCI_D0);

	if (entry->pci.msi_attrib.is_msix) {
		void __iomem *base = pci_msix_desc_addr(entry);

		if (WARN_ON_ONCE(entry->pci.msi_attrib.is_virtual))
			return;

		msg->address_lo = readl(base + PCI_MSIX_ENTRY_LOWER_ADDR);
		msg->address_hi = readl(base + PCI_MSIX_ENTRY_UPPER_ADDR);
		msg->data = readl(base + PCI_MSIX_ENTRY_DATA);
	} else {
		int pos = dev->msi_cap;
		u16 data;

		pci_read_config_dword(dev, pos + PCI_MSI_ADDRESS_LO,
				      &msg->address_lo);
		if (entry->pci.msi_attrib.is_64) {
			pci_read_config_dword(dev, pos + PCI_MSI_ADDRESS_HI,
					      &msg->address_hi);
			pci_read_config_word(dev, pos + PCI_MSI_DATA_64, &data);
		} else {
			msg->address_hi = 0;
			pci_read_config_word(dev, pos + PCI_MSI_DATA_32, &data);
		}
		msg->data = data;
	}
}

static inline void pci_write_msg_msi(struct pci_dev *dev, struct msi_desc *desc,
				     struct msi_msg *msg)
{
	int pos = dev->msi_cap;
	u16 msgctl;

	pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &msgctl);
	msgctl &= ~PCI_MSI_FLAGS_QSIZE;
	msgctl |= FIELD_PREP(PCI_MSI_FLAGS_QSIZE, desc->pci.msi_attrib.multiple);
	pci_write_config_word(dev, pos + PCI_MSI_FLAGS, msgctl);

	pci_write_config_dword(dev, pos + PCI_MSI_ADDRESS_LO, msg->address_lo);
	if (desc->pci.msi_attrib.is_64) {
		pci_write_config_dword(dev, pos + PCI_MSI_ADDRESS_HI,  msg->address_hi);
		pci_write_config_word(dev, pos + PCI_MSI_DATA_64, msg->data);
	} else {
		pci_write_config_word(dev, pos + PCI_MSI_DATA_32, msg->data);
	}
	/* Ensure that the writes are visible in the device */
	pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &msgctl);
}

static inline void pci_write_msg_msix(struct msi_desc *desc, struct msi_msg *msg)
{
	void __iomem *base = pci_msix_desc_addr(desc);
	u32 ctrl = desc->pci.msix_ctrl;
	bool unmasked = !(ctrl & PCI_MSIX_ENTRY_CTRL_MASKBIT);

	if (desc->pci.msi_attrib.is_virtual)
		return;
	/*
	 * The specification mandates that the entry is masked
	 * when the message is modified:
	 *
	 * "If software changes the Address or Data value of an
	 * entry while the entry is unmasked, the result is
	 * undefined."
	 */
	if (unmasked)
		pci_msix_write_vector_ctrl(desc, ctrl | PCI_MSIX_ENTRY_CTRL_MASKBIT);

	writel(msg->address_lo, base + PCI_MSIX_ENTRY_LOWER_ADDR);
	writel(msg->address_hi, base + PCI_MSIX_ENTRY_UPPER_ADDR);
	writel(msg->data, base + PCI_MSIX_ENTRY_DATA);

	if (unmasked)
		pci_msix_write_vector_ctrl(desc, ctrl);

	/* Ensure that the writes are visible in the device */
	readl(base + PCI_MSIX_ENTRY_DATA);
}

void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
{
	struct pci_dev *dev = msi_desc_to_pci_dev(entry);

	if (dev->current_state != PCI_D0 || pci_dev_is_disconnected(dev)) {
		/* Don't touch the hardware now */
	} else if (entry->pci.msi_attrib.is_msix) {
		pci_write_msg_msix(entry, msg);
	} else {
		pci_write_msg_msi(dev, entry, msg);
	}

	entry->msg = *msg;

	if (entry->write_msi_msg)
		entry->write_msi_msg(entry, entry->write_msi_msg_data);
}

void pci_write_msi_msg(unsigned int irq, struct msi_msg *msg)
{
	struct msi_desc *entry = irq_get_msi_desc(irq);

	__pci_write_msi_msg(entry, msg);
}
EXPORT_SYMBOL_GPL(pci_write_msi_msg);


/* PCI/MSI specific functionality */

static void pci_intx_for_msi(struct pci_dev *dev, int enable)
{
	if (!(dev->dev_flags & PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG))
		pci_intx(dev, enable);
}

static void pci_msi_set_enable(struct pci_dev *dev, int enable)
{
	u16 control;

	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
	control &= ~PCI_MSI_FLAGS_ENABLE;
	if (enable)
		control |= PCI_MSI_FLAGS_ENABLE;
	pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control);
}

static int msi_setup_msi_desc(struct pci_dev *dev, int nvec,
			      struct irq_affinity_desc *masks)
{
	struct msi_desc desc;
	u16 control;

	/* MSI Entry Initialization */
	memset(&desc, 0, sizeof(desc));

	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
	/* Lies, damned lies, and MSIs */
	if (dev->dev_flags & PCI_DEV_FLAGS_HAS_MSI_MASKING)
		control |= PCI_MSI_FLAGS_MASKBIT;
	if (pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY))
		control &= ~PCI_MSI_FLAGS_MASKBIT;

	desc.nvec_used			= nvec;
	desc.pci.msi_attrib.is_64	= !!(control & PCI_MSI_FLAGS_64BIT);
	desc.pci.msi_attrib.can_mask	= !!(control & PCI_MSI_FLAGS_MASKBIT);
	desc.pci.msi_attrib.default_irq	= dev->irq;
	desc.pci.msi_attrib.multi_cap	= FIELD_GET(PCI_MSI_FLAGS_QMASK, control);
	desc.pci.msi_attrib.multiple	= ilog2(__roundup_pow_of_two(nvec));
	desc.affinity			= masks;

	if (control & PCI_MSI_FLAGS_64BIT)
		desc.pci.mask_pos = dev->msi_cap + PCI_MSI_MASK_64;
	else
		desc.pci.mask_pos = dev->msi_cap + PCI_MSI_MASK_32;

	/* Save the initial mask status */
	if (desc.pci.msi_attrib.can_mask)
		pci_read_config_dword(dev, desc.pci.mask_pos, &desc.pci.msi_mask);

	return msi_insert_msi_desc(&dev->dev, &desc);
}

static int msi_verify_entries(struct pci_dev *dev)
{
	struct msi_desc *entry;

	if (!dev->no_64bit_msi)
		return 0;

	msi_for_each_desc(entry, &dev->dev, MSI_DESC_ALL) {
		if (entry->msg.address_hi) {
			pci_err(dev, "arch assigned 64-bit MSI address %#x%08x but device only supports 32 bits\n",
				entry->msg.address_hi, entry->msg.address_lo);
			break;
		}
	}
	return !entry ? 0 : -EIO;
}

/**
 * msi_capability_init - configure device's MSI capability structure
 * @dev: pointer to the pci_dev data structure of MSI device function
 * @nvec: number of interrupts to allocate
 * @affd: description of automatic IRQ affinity assignments (may be %NULL)
 *
 * Setup the MSI capability structure of the device with the requested
 * number of interrupts.  A return value of zero indicates the successful
 * setup of an entry with the new MSI IRQ.  A negative return value indicates
 * an error, and a positive return value indicates the number of interrupts
 * which could have been allocated.
 */
static int msi_capability_init(struct pci_dev *dev, int nvec,
			       struct irq_affinity *affd)
{
	struct irq_affinity_desc *masks = NULL;
	struct msi_desc *entry, desc;
	int ret;

	/* Reject multi-MSI early on irq domain enabled architectures */
	if (nvec > 1 && !pci_msi_domain_supports(dev, MSI_FLAG_MULTI_PCI_MSI, ALLOW_LEGACY))
		return 1;

	/*
	 * Disable MSI during setup in the hardware, but mark it enabled
	 * so that setup code can evaluate it.
	 */
	pci_msi_set_enable(dev, 0);
	dev->msi_enabled = 1;

	if (affd)
		masks = irq_create_affinity_masks(nvec, affd);

	msi_lock_descs(&dev->dev);
	ret = msi_setup_msi_desc(dev, nvec, masks);
	if (ret)
		goto fail;

	/* All MSIs are unmasked by default; mask them all */
	entry = msi_first_desc(&dev->dev, MSI_DESC_ALL);
	pci_msi_mask(entry, msi_multi_mask(entry));
	/*
	 * Copy the MSI descriptor for the error path because
	 * pci_msi_setup_msi_irqs() will free it for the hierarchical
	 * interrupt domain case.
	 */
	memcpy(&desc, entry, sizeof(desc));

	/* Configure MSI capability structure */
	ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSI);
	if (ret)
		goto err;

	ret = msi_verify_entries(dev);
	if (ret)
		goto err;

	/* Set MSI enabled bits	*/
	pci_intx_for_msi(dev, 0);
	pci_msi_set_enable(dev, 1);

	pcibios_free_irq(dev);
	dev->irq = entry->irq;
	goto unlock;

err:
	pci_msi_unmask(&desc, msi_multi_mask(&desc));
	pci_free_msi_irqs(dev);
fail:
	dev->msi_enabled = 0;
unlock:
	msi_unlock_descs(&dev->dev);
	kfree(masks);
	return ret;
}

int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
			   struct irq_affinity *affd)
{
	int nvec;
	int rc;

	if (!pci_msi_supported(dev, minvec) || dev->current_state != PCI_D0)
		return -EINVAL;

	/* Check whether driver already requested MSI-X IRQs */
	if (dev->msix_enabled) {
		pci_info(dev, "can't enable MSI (MSI-X already enabled)\n");
		return -EINVAL;
	}

	if (maxvec < minvec)
		return -ERANGE;

	if (WARN_ON_ONCE(dev->msi_enabled))
		return -EINVAL;

	/* Test for the availability of MSI support */
	if (!pci_msi_domain_supports(dev, 0, ALLOW_LEGACY))
		return -ENOTSUPP;

	nvec = pci_msi_vec_count(dev);
	if (nvec < 0)
		return nvec;
	if (nvec < minvec)
		return -ENOSPC;

	if (nvec > maxvec)
		nvec = maxvec;

	rc = pci_setup_msi_context(dev);
	if (rc)
		return rc;

	if (!pci_setup_msi_device_domain(dev))
		return -ENODEV;

	for (;;) {
		if (affd) {
			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
			if (nvec < minvec)
				return -ENOSPC;
		}

		rc = msi_capability_init(dev, nvec, affd);
		if (rc == 0)
			return nvec;

		if (rc < 0)
			return rc;
		if (rc < minvec)
			return -ENOSPC;

		nvec = rc;
	}
}

/**
 * pci_msi_vec_count - Return the number of MSI vectors a device can send
 * @dev: device to report about
 *
 * This function returns the number of MSI vectors a device requested via
 * Multiple Message Capable register. It returns a negative errno if the
 * device is not capable sending MSI interrupts. Otherwise, the call succeeds
 * and returns a power of two, up to a maximum of 2^5 (32), according to the
 * MSI specification.
 **/
int pci_msi_vec_count(struct pci_dev *dev)
{
	int ret;
	u16 msgctl;

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

	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &msgctl);
	ret = 1 << FIELD_GET(PCI_MSI_FLAGS_QMASK, msgctl);

	return ret;
}
EXPORT_SYMBOL(pci_msi_vec_count);

/*
 * Architecture override returns true when the PCI MSI message should be
 * written by the generic restore function.
 */
bool __weak arch_restore_msi_irqs(struct pci_dev *dev)
{
	return true;
}

void __pci_restore_msi_state(struct pci_dev *dev)
{
	struct msi_desc *entry;
	u16 control;

	if (!dev->msi_enabled)
		return;

	entry = irq_get_msi_desc(dev->irq);

	pci_intx_for_msi(dev, 0);
	pci_msi_set_enable(dev, 0);
	if (arch_restore_msi_irqs(dev))
		__pci_write_msi_msg(entry, &entry->msg);

	pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
	pci_msi_update_mask(entry, 0, 0);
	control &= ~PCI_MSI_FLAGS_QSIZE;
	control |= PCI_MSI_FLAGS_ENABLE |
		   FIELD_PREP(PCI_MSI_FLAGS_QSIZE, entry->pci.msi_attrib.multiple);
	pci_write_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, control);
}

void pci_msi_shutdown(struct pci_dev *dev)
{
	struct msi_desc *desc;

	if (!pci_msi_enable || !dev || !dev->msi_enabled)
		return;

	pci_msi_set_enable(dev, 0);
	pci_intx_for_msi(dev, 1);
	dev->msi_enabled = 0;

	/* Return the device with MSI unmasked as initial states */
	desc = msi_first_desc(&dev->dev, MSI_DESC_ALL);
	if (!WARN_ON_ONCE(!desc))
		pci_msi_unmask(desc, msi_multi_mask(desc));

	/* Restore dev->irq to its default pin-assertion IRQ */
	dev->irq = desc->pci.msi_attrib.default_irq;
	pcibios_alloc_irq(dev);
}

/* PCI/MSI-X specific functionality */

static void pci_msix_clear_and_set_ctrl(struct pci_dev *dev, u16 clear, u16 set)
{
	u16 ctrl;

	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &ctrl);
	ctrl &= ~clear;
	ctrl |= set;
	pci_write_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, ctrl);
}

static void __iomem *msix_map_region(struct pci_dev *dev,
				     unsigned int nr_entries)
{
	resource_size_t phys_addr;
	u32 table_offset;
	unsigned long flags;
	u8 bir;

	pci_read_config_dword(dev, dev->msix_cap + PCI_MSIX_TABLE,
			      &table_offset);
	bir = (u8)(table_offset & PCI_MSIX_TABLE_BIR);
	flags = pci_resource_flags(dev, bir);
	if (!flags || (flags & IORESOURCE_UNSET))
		return NULL;

	table_offset &= PCI_MSIX_TABLE_OFFSET;
	phys_addr = pci_resource_start(dev, bir) + table_offset;

	return ioremap(phys_addr, nr_entries * PCI_MSIX_ENTRY_SIZE);
}

/**
 * msix_prepare_msi_desc - Prepare a half initialized MSI descriptor for operation
 * @dev:	The PCI device for which the descriptor is prepared
 * @desc:	The MSI descriptor for preparation
 *
 * This is separate from msix_setup_msi_descs() below to handle dynamic
 * allocations for MSI-X after initial enablement.
 *
 * Ideally the whole MSI-X setup would work that way, but there is no way to
 * support this for the legacy arch_setup_msi_irqs() mechanism and for the
 * fake irq domains like the x86 XEN one. Sigh...
 *
 * The descriptor is zeroed and only @desc::msi_index and @desc::affinity
 * are set. When called from msix_setup_msi_descs() then the is_virtual
 * attribute is initialized as well.
 *
 * Fill in the rest.
 */
void msix_prepare_msi_desc(struct pci_dev *dev, struct msi_desc *desc)
{
	desc->nvec_used				= 1;
	desc->pci.msi_attrib.is_msix		= 1;
	desc->pci.msi_attrib.is_64		= 1;
	desc->pci.msi_attrib.default_irq	= dev->irq;
	desc->pci.mask_base			= dev->msix_base;


	if (!pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY) &&
	    !desc->pci.msi_attrib.is_virtual) {
		void __iomem *addr = pci_msix_desc_addr(desc);

		desc->pci.msi_attrib.can_mask = 1;
		/* Workaround for SUN NIU insanity, which requires write before read */
		if (dev->dev_flags & PCI_DEV_FLAGS_MSIX_TOUCH_ENTRY_DATA_FIRST)
			writel(0, addr + PCI_MSIX_ENTRY_DATA);
		desc->pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
	}
}

static int msix_setup_msi_descs(struct pci_dev *dev, struct msix_entry *entries,
				int nvec, struct irq_affinity_desc *masks)
{
	int ret = 0, i, vec_count = pci_msix_vec_count(dev);
	struct irq_affinity_desc *curmsk;
	struct msi_desc desc;

	memset(&desc, 0, sizeof(desc));

	for (i = 0, curmsk = masks; i < nvec; i++, curmsk++) {
		desc.msi_index = entries ? entries[i].entry : i;
		desc.affinity = masks ? curmsk : NULL;
		desc.pci.msi_attrib.is_virtual = desc.msi_index >= vec_count;

		msix_prepare_msi_desc(dev, &desc);

		ret = msi_insert_msi_desc(&dev->dev, &desc);
		if (ret)
			break;
	}
	return ret;
}

static void msix_update_entries(struct pci_dev *dev, struct msix_entry *entries)
{
	struct msi_desc *desc;

	if (entries) {
		msi_for_each_desc(desc, &dev->dev, MSI_DESC_ALL) {
			entries->vector = desc->irq;
			entries++;
		}
	}
}

static void msix_mask_all(void __iomem *base, int tsize)
{
	u32 ctrl = PCI_MSIX_ENTRY_CTRL_MASKBIT;
	int i;

	for (i = 0; i < tsize; i++, base += PCI_MSIX_ENTRY_SIZE)
		writel(ctrl, base + PCI_MSIX_ENTRY_VECTOR_CTRL);
}

static int msix_setup_interrupts(struct pci_dev *dev, struct msix_entry *entries,
				 int nvec, struct irq_affinity *affd)
{
	struct irq_affinity_desc *masks = NULL;
	int ret;

	if (affd)
		masks = irq_create_affinity_masks(nvec, affd);

	msi_lock_descs(&dev->dev);
	ret = msix_setup_msi_descs(dev, entries, nvec, masks);
	if (ret)
		goto out_free;

	ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
	if (ret)
		goto out_free;

	/* Check if all MSI entries honor device restrictions */
	ret = msi_verify_entries(dev);
	if (ret)
		goto out_free;

	msix_update_entries(dev, entries);
	goto out_unlock;

out_free:
	pci_free_msi_irqs(dev);
out_unlock:
	msi_unlock_descs(&dev->dev);
	kfree(masks);
	return ret;
}

/**
 * msix_capability_init - configure device's MSI-X capability
 * @dev: pointer to the pci_dev data structure of MSI-X device function
 * @entries: pointer to an array of struct msix_entry entries
 * @nvec: number of @entries
 * @affd: Optional pointer to enable automatic affinity assignment
 *
 * Setup the MSI-X capability structure of device function with a
 * single MSI-X IRQ. A return of zero indicates the successful setup of
 * requested MSI-X entries with allocated IRQs or non-zero for otherwise.
 **/
static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
				int nvec, struct irq_affinity *affd)
{
	int ret, tsize;
	u16 control;

	/*
	 * Some devices require MSI-X to be enabled before the MSI-X
	 * registers can be accessed.  Mask all the vectors to prevent
	 * interrupts coming in before they're fully set up.
	 */
	pci_msix_clear_and_set_ctrl(dev, 0, PCI_MSIX_FLAGS_MASKALL |
				    PCI_MSIX_FLAGS_ENABLE);

	/* Mark it enabled so setup functions can query it */
	dev->msix_enabled = 1;

	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
	/* Request & Map MSI-X table region */
	tsize = msix_table_size(control);
	dev->msix_base = msix_map_region(dev, tsize);
	if (!dev->msix_base) {
		ret = -ENOMEM;
		goto out_disable;
	}

	ret = msix_setup_interrupts(dev, entries, nvec, affd);
	if (ret)
		goto out_disable;

	/* Disable INTX */
	pci_intx_for_msi(dev, 0);

	if (!pci_msi_domain_supports(dev, MSI_FLAG_NO_MASK, DENY_LEGACY)) {
		/*
		 * Ensure that all table entries are masked to prevent
		 * stale entries from firing in a crash kernel.
		 *
		 * Done late to deal with a broken Marvell NVME device
		 * which takes the MSI-X mask bits into account even
		 * when MSI-X is disabled, which prevents MSI delivery.
		 */
		msix_mask_all(dev->msix_base, tsize);
	}
	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);

	pcibios_free_irq(dev);
	return 0;

out_disable:
	dev->msix_enabled = 0;
	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL | PCI_MSIX_FLAGS_ENABLE, 0);

	return ret;
}

static bool pci_msix_validate_entries(struct pci_dev *dev, struct msix_entry *entries, int nvec)
{
	bool nogap;
	int i, j;

	if (!entries)
		return true;

	nogap = pci_msi_domain_supports(dev, MSI_FLAG_MSIX_CONTIGUOUS, DENY_LEGACY);

	for (i = 0; i < nvec; i++) {
		/* Check for duplicate entries */
		for (j = i + 1; j < nvec; j++) {
			if (entries[i].entry == entries[j].entry)
				return false;
		}
		/* Check for unsupported gaps */
		if (nogap && entries[i].entry != i)
			return false;
	}
	return true;
}

int __pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries, int minvec,
			    int maxvec, struct irq_affinity *affd, int flags)
{
	int hwsize, rc, nvec = maxvec;

	if (maxvec < minvec)
		return -ERANGE;

	if (dev->msi_enabled) {
		pci_info(dev, "can't enable MSI-X (MSI already enabled)\n");
		return -EINVAL;
	}

	if (WARN_ON_ONCE(dev->msix_enabled))
		return -EINVAL;

	/* Check MSI-X early on irq domain enabled architectures */
	if (!pci_msi_domain_supports(dev, MSI_FLAG_PCI_MSIX, ALLOW_LEGACY))
		return -ENOTSUPP;

	if (!pci_msi_supported(dev, nvec) || dev->current_state != PCI_D0)
		return -EINVAL;

	hwsize = pci_msix_vec_count(dev);
	if (hwsize < 0)
		return hwsize;

	if (!pci_msix_validate_entries(dev, entries, nvec))
		return -EINVAL;

	if (hwsize < nvec) {
		/* Keep the IRQ virtual hackery working */
		if (flags & PCI_IRQ_VIRTUAL)
			hwsize = nvec;
		else
			nvec = hwsize;
	}

	if (nvec < minvec)
		return -ENOSPC;

	rc = pci_setup_msi_context(dev);
	if (rc)
		return rc;

	if (!pci_setup_msix_device_domain(dev, hwsize))
		return -ENODEV;

	for (;;) {
		if (affd) {
			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
			if (nvec < minvec)
				return -ENOSPC;
		}

		rc = msix_capability_init(dev, entries, nvec, affd);
		if (rc == 0)
			return nvec;

		if (rc < 0)
			return rc;
		if (rc < minvec)
			return -ENOSPC;

		nvec = rc;
	}
}

void __pci_restore_msix_state(struct pci_dev *dev)
{
	struct msi_desc *entry;
	bool write_msg;

	if (!dev->msix_enabled)
		return;

	/* route the table */
	pci_intx_for_msi(dev, 0);
	pci_msix_clear_and_set_ctrl(dev, 0,
				PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL);

	write_msg = arch_restore_msi_irqs(dev);

	msi_lock_descs(&dev->dev);
	msi_for_each_desc(entry, &dev->dev, MSI_DESC_ALL) {
		if (write_msg)
			__pci_write_msi_msg(entry, &entry->msg);
		pci_msix_write_vector_ctrl(entry, entry->pci.msix_ctrl);
	}
	msi_unlock_descs(&dev->dev);

	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
}

void pci_msix_shutdown(struct pci_dev *dev)
{
	struct msi_desc *desc;

	if (!pci_msi_enable || !dev || !dev->msix_enabled)
		return;

	if (pci_dev_is_disconnected(dev)) {
		dev->msix_enabled = 0;
		return;
	}

	/* Return the device with MSI-X masked as initial states */
	msi_for_each_desc(desc, &dev->dev, MSI_DESC_ALL)
		pci_msix_mask(desc);

	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
	pci_intx_for_msi(dev, 1);
	dev->msix_enabled = 0;
	pcibios_alloc_irq(dev);
}

/* Common interfaces */

void pci_free_msi_irqs(struct pci_dev *dev)
{
	pci_msi_teardown_msi_irqs(dev);

	if (dev->msix_base) {
		iounmap(dev->msix_base);
		dev->msix_base = NULL;
	}
}

/* Misc. infrastructure */

struct pci_dev *msi_desc_to_pci_dev(struct msi_desc *desc)
{
	return to_pci_dev(desc->dev);
}
EXPORT_SYMBOL(msi_desc_to_pci_dev);

void pci_no_msi(void)
{
	pci_msi_enable = 0;
}