linux/drivers/pci/rebar.c

// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Resizable BAR Extended Capability handling.
 */

#include <linux/bits.h>
#include <linux/bitfield.h>
#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/ioport.h>
#include <linux/log2.h>
#include <linux/pci.h>
#include <linux/sizes.h>
#include <linux/types.h>

#include "pci.h"

#define PCI_REBAR_MIN_SIZE	((resource_size_t)SZ_1M)

/**
 * pci_rebar_bytes_to_size - Convert size in bytes to PCI BAR Size
 * @bytes: size in bytes
 *
 * Convert size in bytes to encoded BAR Size in Resizable BAR Capability
 * (PCIe r6.2, sec. 7.8.6.3).
 *
 * Return: encoded BAR Size as defined in the PCIe spec (0=1MB, 31=128TB)
 */
int pci_rebar_bytes_to_size(u64 bytes)
{
	int rebar_minsize = ilog2(PCI_REBAR_MIN_SIZE);

	bytes = roundup_pow_of_two(bytes);

	return max(ilog2(bytes), rebar_minsize) - rebar_minsize;
}
EXPORT_SYMBOL_GPL(pci_rebar_bytes_to_size);

/**
 * pci_rebar_size_to_bytes - Convert encoded BAR Size to size in bytes
 * @size: encoded BAR Size as defined in the PCIe spec (0=1MB, 31=128TB)
 *
 * Return: BAR size in bytes
 */
resource_size_t pci_rebar_size_to_bytes(int size)
{
	return 1ULL << (size + ilog2(PCI_REBAR_MIN_SIZE));
}
EXPORT_SYMBOL_GPL(pci_rebar_size_to_bytes);

void pci_rebar_init(struct pci_dev *pdev)
{
	pdev->rebar_cap = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_REBAR);
}

/**
 * pci_rebar_find_pos - find position of resize control reg for BAR
 * @pdev: PCI device
 * @bar: BAR to find
 *
 * Helper to find the position of the control register for a BAR.
 *
 * Return:
 * * %-ENOTSUPP if resizable BARs are not supported at all,
 * * %-ENOENT if no control register for the BAR could be found.
 */
static int pci_rebar_find_pos(struct pci_dev *pdev, int bar)
{
	unsigned int pos, nbars, i;
	u32 ctrl;

	if (pci_resource_is_iov(bar)) {
		pos = pci_iov_vf_rebar_cap(pdev);
		bar = pci_resource_num_to_vf_bar(bar);
	} else {
		pos = pdev->rebar_cap;
	}

	if (!pos)
		return -ENOTSUPP;

	pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
	nbars = FIELD_GET(PCI_REBAR_CTRL_NBAR_MASK, ctrl);

	for (i = 0; i < nbars; i++, pos += 8) {
		int bar_idx;

		pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
		bar_idx = FIELD_GET(PCI_REBAR_CTRL_BAR_IDX, ctrl);
		if (bar_idx == bar)
			return pos;
	}

	return -ENOENT;
}

/**
 * pci_rebar_get_possible_sizes - get possible sizes for Resizable BAR
 * @pdev: PCI device
 * @bar: BAR to query
 *
 * Get the possible sizes of a resizable BAR as bitmask.
 *
 * Return: A bitmask of possible sizes (bit 0=1MB, bit 31=128TB), or %0 if
 *	   BAR isn't resizable.
 */
u64 pci_rebar_get_possible_sizes(struct pci_dev *pdev, int bar)
{
	int pos;
	u32 cap;

	pos = pci_rebar_find_pos(pdev, bar);
	if (pos < 0)
		return 0;

	pci_read_config_dword(pdev, pos + PCI_REBAR_CAP, &cap);
	cap = FIELD_GET(PCI_REBAR_CAP_SIZES, cap);

	/* Sapphire RX 5600 XT Pulse has an invalid cap dword for BAR 0 */
	if (pdev->vendor == PCI_VENDOR_ID_ATI && pdev->device == 0x731f &&
	    bar == 0 && cap == 0x700)
		return 0x3f00;

	return cap;
}
EXPORT_SYMBOL(pci_rebar_get_possible_sizes);

/**
 * pci_rebar_size_supported - check if size is supported for BAR
 * @pdev: PCI device
 * @bar: BAR to check
 * @size: encoded size as defined in the PCIe spec (0=1MB, 31=128TB)
 *
 * Return: %true if @bar is resizable and @size is supported, otherwise
 *	   %false.
 */
bool pci_rebar_size_supported(struct pci_dev *pdev, int bar, int size)
{
	u64 sizes = pci_rebar_get_possible_sizes(pdev, bar);

	if (size < 0 || size > ilog2(SZ_128T) - ilog2(PCI_REBAR_MIN_SIZE))
		return false;

	return BIT(size) & sizes;
}
EXPORT_SYMBOL_GPL(pci_rebar_size_supported);

/**
 * pci_rebar_get_max_size - get the maximum supported size of a BAR
 * @pdev: PCI device
 * @bar: BAR to query
 *
 * Get the largest supported size of a resizable BAR as a size.
 *
 * Return: the encoded maximum BAR size as defined in the PCIe spec
 *	   (0=1MB, 31=128TB), or %-NOENT on error.
 */
int pci_rebar_get_max_size(struct pci_dev *pdev, int bar)
{
	u64 sizes;

	sizes = pci_rebar_get_possible_sizes(pdev, bar);
	if (!sizes)
		return -ENOENT;

	return __fls(sizes);
}
EXPORT_SYMBOL_GPL(pci_rebar_get_max_size);

/**
 * pci_rebar_get_current_size - get the current size of a Resizable BAR
 * @pdev: PCI device
 * @bar: BAR to get the size from
 *
 * Read the current size of a BAR from the Resizable BAR config.
 *
 * Return: BAR Size if @bar is resizable (0=1MB, 31=128TB), or negative on
 *         error.
 */
int pci_rebar_get_current_size(struct pci_dev *pdev, int bar)
{
	int pos;
	u32 ctrl;

	pos = pci_rebar_find_pos(pdev, bar);
	if (pos < 0)
		return pos;

	pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
	return FIELD_GET(PCI_REBAR_CTRL_BAR_SIZE, ctrl);
}

/**
 * pci_rebar_set_size - set a new size for a Resizable BAR
 * @pdev: PCI device
 * @bar: BAR to set size to
 * @size: new size as defined in the PCIe spec (0=1MB, 31=128TB)
 *
 * Set the new size of a BAR as defined in the spec.
 *
 * Return: %0 if resizing was successful, or negative on error.
 */
int pci_rebar_set_size(struct pci_dev *pdev, int bar, int size)
{
	int pos;
	u32 ctrl;

	pos = pci_rebar_find_pos(pdev, bar);
	if (pos < 0)
		return pos;

	pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
	ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
	ctrl |= FIELD_PREP(PCI_REBAR_CTRL_BAR_SIZE, size);
	pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);

	if (pci_resource_is_iov(bar))
		pci_iov_resource_set_size(pdev, bar, size);

	return 0;
}

void pci_restore_rebar_state(struct pci_dev *pdev)
{
	unsigned int pos, nbars, i;
	u32 ctrl;

	pos = pdev->rebar_cap;
	if (!pos)
		return;

	pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
	nbars = FIELD_GET(PCI_REBAR_CTRL_NBAR_MASK, ctrl);

	for (i = 0; i < nbars; i++, pos += 8) {
		struct resource *res;
		int bar_idx, size;

		pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl);
		bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX;
		res = pci_resource_n(pdev, bar_idx);
		size = pci_rebar_bytes_to_size(resource_size(res));
		ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
		ctrl |= FIELD_PREP(PCI_REBAR_CTRL_BAR_SIZE, size);
		pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
	}
}

static bool pci_resize_is_memory_decoding_enabled(struct pci_dev *dev,
						  int resno)
{
	u16 cmd;

	if (pci_resource_is_iov(resno))
		return pci_iov_is_memory_decoding_enabled(dev);

	pci_read_config_word(dev, PCI_COMMAND, &cmd);

	return cmd & PCI_COMMAND_MEMORY;
}

void pci_resize_resource_set_size(struct pci_dev *dev, int resno, int size)
{
	resource_size_t res_size = pci_rebar_size_to_bytes(size);
	struct resource *res = pci_resource_n(dev, resno);

	if (pci_resource_is_iov(resno))
		res_size *= pci_sriov_get_totalvfs(dev);

	resource_set_size(res, res_size);
}

/**
 * pci_resize_resource - reconfigure a Resizable BAR and resources
 * @dev: the PCI device
 * @resno: index of the BAR to be resized
 * @size: new size as defined in the spec (0=1MB, 31=128TB)
 * @exclude_bars: a mask of BARs that should not be released
 *
 * Reconfigure @resno to @size and re-run resource assignment algorithm
 * with the new size.
 *
 * Prior to resize, release @dev resources that share a bridge window with
 * @resno.  This unpins the bridge window resource to allow changing it.
 *
 * The caller may prevent releasing a particular BAR by providing
 * @exclude_bars mask, but this may result in the resize operation failing
 * due to insufficient space.
 *
 * Return: 0 on success, or negative on error. In case of an error, the
 *         resources are restored to their original places.
 */
int pci_resize_resource(struct pci_dev *dev, int resno, int size,
			int exclude_bars)
{
	struct pci_host_bridge *host;
	int old, ret;

	/* Check if we must preserve the firmware's resource assignment */
	host = pci_find_host_bridge(dev->bus);
	if (host->preserve_config)
		return -ENOTSUPP;

	if (pci_resize_is_memory_decoding_enabled(dev, resno))
		return -EBUSY;

	if (!pci_rebar_size_supported(dev, resno, size))
		return -EINVAL;

	old = pci_rebar_get_current_size(dev, resno);
	if (old < 0)
		return old;

	ret = pci_rebar_set_size(dev, resno, size);
	if (ret)
		return ret;

	ret = pci_do_resource_release_and_resize(dev, resno, size, exclude_bars);
	if (ret)
		goto error_resize;
	return 0;

error_resize:
	pci_rebar_set_size(dev, resno, old);
	return ret;
}
EXPORT_SYMBOL(pci_resize_resource);