xref: /linux/drivers/cxl/core/pci.c (revision e812928be2ee1c2744adf20ed04e0ce1e2fc5c13)

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
#include <linux/units.h>
#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/pci.h>
#include <linux/pci-doe.h>
#include <linux/aer.h>
#include <cxlpci.h>
#include <cxlmem.h>
#include <cxl.h>
#include "core.h"
#include "trace.h"

/**
 * DOC: cxl core pci
 *
 * Compute Express Link protocols are layered on top of PCIe. CXL core provides
 * a set of helpers for CXL interactions which occur via PCIe.
 */

static unsigned short media_ready_timeout = 60;
module_param(media_ready_timeout, ushort, 0644);
MODULE_PARM_DESC(media_ready_timeout, "seconds to wait for media ready");

static int pci_get_port_num(struct pci_dev *pdev)
{
	u32 lnkcap;
	int type;

	type = pci_pcie_type(pdev);
	if (type != PCI_EXP_TYPE_DOWNSTREAM && type != PCI_EXP_TYPE_ROOT_PORT)
		return -EINVAL;

	if (pci_read_config_dword(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCAP,
				  &lnkcap))
		return -ENXIO;

	return FIELD_GET(PCI_EXP_LNKCAP_PN, lnkcap);
}

/**
 * devm_cxl_add_dport_by_dev - allocate a dport by dport device
 * @port: cxl_port that hosts the dport
 * @dport_dev: 'struct device' of the dport
 *
 * Returns the allocated dport on success or ERR_PTR() of -errno on error
 */
struct cxl_dport *devm_cxl_add_dport_by_dev(struct cxl_port *port,
					    struct device *dport_dev)
{
	struct cxl_register_map map;
	struct pci_dev *pdev;
	int port_num, rc;

	if (!dev_is_pci(dport_dev))
		return ERR_PTR(-EINVAL);

	pdev = to_pci_dev(dport_dev);
	port_num = pci_get_port_num(pdev);
	if (port_num < 0)
		return ERR_PTR(port_num);

	rc = cxl_find_regblock(pdev, CXL_REGLOC_RBI_COMPONENT, &map);
	if (rc)
		return ERR_PTR(rc);

	device_lock_assert(&port->dev);
	return devm_cxl_add_dport(port, dport_dev, port_num, map.resource);
}
EXPORT_SYMBOL_NS_GPL(devm_cxl_add_dport_by_dev, "CXL");

static int cxl_dvsec_mem_range_valid(struct cxl_dev_state *cxlds, int id)
{
	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
	int d = cxlds->cxl_dvsec;
	bool valid = false;
	int rc, i;
	u32 temp;

	if (id > CXL_DVSEC_RANGE_MAX)
		return -EINVAL;

	/* Check MEM INFO VALID bit first, give up after 1s */
	i = 1;
	do {
		rc = pci_read_config_dword(pdev,
					   d + PCI_DVSEC_CXL_RANGE_SIZE_LOW(id),
					   &temp);
		if (rc)
			return rc;

		valid = FIELD_GET(PCI_DVSEC_CXL_MEM_INFO_VALID, temp);
		if (valid)
			break;
		msleep(1000);
	} while (i--);

	if (!valid) {
		dev_err(&pdev->dev,
			"Timeout awaiting memory range %d valid after 1s.\n",
			id);
		return -ETIMEDOUT;
	}

	return 0;
}

static int cxl_dvsec_mem_range_active(struct cxl_dev_state *cxlds, int id)
{
	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
	int d = cxlds->cxl_dvsec;
	bool active = false;
	int rc, i;
	u32 temp;

	if (id > CXL_DVSEC_RANGE_MAX)
		return -EINVAL;

	/* Check MEM ACTIVE bit, up to 60s timeout by default */
	for (i = media_ready_timeout; i; i--) {
		rc = pci_read_config_dword(
			pdev, d + PCI_DVSEC_CXL_RANGE_SIZE_LOW(id), &temp);
		if (rc)
			return rc;

		active = FIELD_GET(PCI_DVSEC_CXL_MEM_ACTIVE, temp);
		if (active)
			break;
		msleep(1000);
	}

	if (!active) {
		dev_err(&pdev->dev,
			"timeout awaiting memory active after %d seconds\n",
			media_ready_timeout);
		return -ETIMEDOUT;
	}

	return 0;
}

/*
 * Wait up to @media_ready_timeout for the device to report memory
 * active.
 */
int cxl_await_media_ready(struct cxl_dev_state *cxlds)
{
	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
	int d = cxlds->cxl_dvsec;
	int rc, i, hdm_count;
	u64 md_status;
	u16 cap;

	rc = pci_read_config_word(pdev,
				  d + PCI_DVSEC_CXL_CAP, &cap);
	if (rc)
		return rc;

	hdm_count = FIELD_GET(PCI_DVSEC_CXL_HDM_COUNT, cap);
	for (i = 0; i < hdm_count; i++) {
		rc = cxl_dvsec_mem_range_valid(cxlds, i);
		if (rc)
			return rc;
	}

	for (i = 0; i < hdm_count; i++) {
		rc = cxl_dvsec_mem_range_active(cxlds, i);
		if (rc)
			return rc;
	}

	md_status = readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET);
	if (!CXLMDEV_READY(md_status))
		return -EIO;

	return 0;
}
EXPORT_SYMBOL_NS_GPL(cxl_await_media_ready, "CXL");

static int cxl_set_mem_enable(struct cxl_dev_state *cxlds, u16 val)
{
	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
	int d = cxlds->cxl_dvsec;
	u16 ctrl;
	int rc;

	rc = pci_read_config_word(pdev, d + PCI_DVSEC_CXL_CTRL, &ctrl);
	if (rc < 0)
		return rc;

	if ((ctrl & PCI_DVSEC_CXL_MEM_ENABLE) == val)
		return 1;
	ctrl &= ~PCI_DVSEC_CXL_MEM_ENABLE;
	ctrl |= val;

	rc = pci_write_config_word(pdev, d + PCI_DVSEC_CXL_CTRL, ctrl);
	if (rc < 0)
		return rc;

	return 0;
}

static void clear_mem_enable(void *cxlds)
{
	cxl_set_mem_enable(cxlds, 0);
}

static int devm_cxl_enable_mem(struct device *host, struct cxl_dev_state *cxlds)
{
	int rc;

	rc = cxl_set_mem_enable(cxlds, PCI_DVSEC_CXL_MEM_ENABLE);
	if (rc < 0)
		return rc;
	if (rc > 0)
		return 0;
	return devm_add_action_or_reset(host, clear_mem_enable, cxlds);
}

/* require dvsec ranges to be covered by a locked platform window */
static int dvsec_range_allowed(struct device *dev, const void *arg)
{
	const struct range *dev_range = arg;
	struct cxl_decoder *cxld;

	if (!is_root_decoder(dev))
		return 0;

	cxld = to_cxl_decoder(dev);

	if (!(cxld->flags & CXL_DECODER_F_RAM))
		return 0;

	return range_contains(&cxld->hpa_range, dev_range);
}

static void disable_hdm(void *_cxlhdm)
{
	u32 global_ctrl;
	struct cxl_hdm *cxlhdm = _cxlhdm;
	void __iomem *hdm = cxlhdm->regs.hdm_decoder;

	global_ctrl = readl(hdm + CXL_HDM_DECODER_CTRL_OFFSET);
	writel(global_ctrl & ~CXL_HDM_DECODER_ENABLE,
	       hdm + CXL_HDM_DECODER_CTRL_OFFSET);
}

static int devm_cxl_enable_hdm(struct device *host, struct cxl_hdm *cxlhdm)
{
	void __iomem *hdm = cxlhdm->regs.hdm_decoder;
	u32 global_ctrl;

	global_ctrl = readl(hdm + CXL_HDM_DECODER_CTRL_OFFSET);
	writel(global_ctrl | CXL_HDM_DECODER_ENABLE,
	       hdm + CXL_HDM_DECODER_CTRL_OFFSET);

	return devm_add_action_or_reset(host, disable_hdm, cxlhdm);
}

int cxl_dvsec_rr_decode(struct cxl_dev_state *cxlds,
			struct cxl_endpoint_dvsec_info *info)
{
	struct pci_dev *pdev = to_pci_dev(cxlds->dev);
	struct device *dev = cxlds->dev;
	int hdm_count, rc, i, ranges = 0;
	int d = cxlds->cxl_dvsec;
	u16 cap, ctrl;

	if (!d) {
		dev_dbg(dev, "No DVSEC Capability\n");
		return -ENXIO;
	}

	rc = pci_read_config_word(pdev, d + PCI_DVSEC_CXL_CAP, &cap);
	if (rc)
		return rc;

	if (!(cap & PCI_DVSEC_CXL_MEM_CAPABLE)) {
		dev_dbg(dev, "Not MEM Capable\n");
		return -ENXIO;
	}

	/*
	 * It is not allowed by spec for MEM.capable to be set and have 0 legacy
	 * HDM decoders (values > 2 are also undefined as of CXL 2.0). As this
	 * driver is for a spec defined class code which must be CXL.mem
	 * capable, there is no point in continuing to enable CXL.mem.
	 */
	hdm_count = FIELD_GET(PCI_DVSEC_CXL_HDM_COUNT, cap);
	if (!hdm_count || hdm_count > 2)
		return -EINVAL;

	/*
	 * The current DVSEC values are moot if the memory capability is
	 * disabled, and they will remain moot after the HDM Decoder
	 * capability is enabled.
	 */
	rc = pci_read_config_word(pdev, d + PCI_DVSEC_CXL_CTRL, &ctrl);
	if (rc)
		return rc;

	info->mem_enabled = FIELD_GET(PCI_DVSEC_CXL_MEM_ENABLE, ctrl);
	if (!info->mem_enabled)
		return 0;

	for (i = 0; i < hdm_count; i++) {
		u64 base, size;
		u32 temp;

		rc = cxl_dvsec_mem_range_valid(cxlds, i);
		if (rc)
			return rc;

		rc = pci_read_config_dword(
			pdev, d + PCI_DVSEC_CXL_RANGE_SIZE_HIGH(i), &temp);
		if (rc)
			return rc;

		size = (u64)temp << 32;

		rc = pci_read_config_dword(
			pdev, d + PCI_DVSEC_CXL_RANGE_SIZE_LOW(i), &temp);
		if (rc)
			return rc;

		size |= temp & PCI_DVSEC_CXL_MEM_SIZE_LOW;
		if (!size) {
			continue;
		}

		rc = pci_read_config_dword(
			pdev, d + PCI_DVSEC_CXL_RANGE_BASE_HIGH(i), &temp);
		if (rc)
			return rc;

		base = (u64)temp << 32;

		rc = pci_read_config_dword(
			pdev, d + PCI_DVSEC_CXL_RANGE_BASE_LOW(i), &temp);
		if (rc)
			return rc;

		base |= temp & PCI_DVSEC_CXL_MEM_BASE_LOW;

		info->dvsec_range[ranges++] = (struct range) {
			.start = base,
			.end = base + size - 1
		};
	}

	info->ranges = ranges;

	return 0;
}
EXPORT_SYMBOL_NS_GPL(cxl_dvsec_rr_decode, "CXL");

/**
 * cxl_hdm_decode_init() - Setup HDM decoding for the endpoint
 * @cxlds: Device state
 * @cxlhdm: Mapped HDM decoder Capability
 * @info: Cached DVSEC range registers info
 *
 * Try to enable the endpoint's HDM Decoder Capability
 */
int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
			struct cxl_endpoint_dvsec_info *info)
{
	void __iomem *hdm = cxlhdm->regs.hdm_decoder;
	struct cxl_port *port = cxlhdm->port;
	struct device *dev = cxlds->dev;
	struct cxl_port *root;
	int i, rc, allowed;
	u32 global_ctrl = 0;

	if (hdm)
		global_ctrl = readl(hdm + CXL_HDM_DECODER_CTRL_OFFSET);

	/*
	 * If the HDM Decoder Capability is already enabled then assume
	 * that some other agent like platform firmware set it up.
	 */
	if (global_ctrl & CXL_HDM_DECODER_ENABLE || (!hdm && info->mem_enabled))
		return devm_cxl_enable_mem(&port->dev, cxlds);

	/*
	 * If the HDM Decoder Capability does not exist and DVSEC was
	 * not setup, the DVSEC based emulation cannot be used.
	 */
	if (!hdm)
		return -ENODEV;

	/* The HDM Decoder Capability exists but is globally disabled. */

	/*
	 * If the DVSEC CXL Range registers are not enabled, just
	 * enable and use the HDM Decoder Capability registers.
	 */
	if (!info->mem_enabled) {
		rc = devm_cxl_enable_hdm(&port->dev, cxlhdm);
		if (rc)
			return rc;

		return devm_cxl_enable_mem(&port->dev, cxlds);
	}

	/*
	 * Per CXL 2.0 Section 8.1.3.8.3 and 8.1.3.8.4 DVSEC CXL Range 1 Base
	 * [High,Low] when HDM operation is enabled the range register values
	 * are ignored by the device, but the spec also recommends matching the
	 * DVSEC Range 1,2 to HDM Decoder Range 0,1. So, non-zero info->ranges
	 * are expected even though Linux does not require or maintain that
	 * match. Check if at least one DVSEC range is enabled and allowed by
	 * the platform. That is, the DVSEC range must be covered by a locked
	 * platform window (CFMWS). Fail otherwise as the endpoint's decoders
	 * cannot be used.
	 */

	root = to_cxl_port(port->dev.parent);
	while (!is_cxl_root(root) && is_cxl_port(root->dev.parent))
		root = to_cxl_port(root->dev.parent);
	if (!is_cxl_root(root)) {
		dev_err(dev, "Failed to acquire root port for HDM enable\n");
		return -ENODEV;
	}

	for (i = 0, allowed = 0; i < info->ranges; i++) {
		struct device *cxld_dev;

		cxld_dev = device_find_child(&root->dev, &info->dvsec_range[i],
					     dvsec_range_allowed);
		if (!cxld_dev) {
			dev_dbg(dev, "DVSEC Range%d denied by platform\n", i);
			continue;
		}
		dev_dbg(dev, "DVSEC Range%d allowed by platform\n", i);
		put_device(cxld_dev);
		allowed++;
	}

	if (!allowed) {
		dev_err(dev, "Range register decodes outside platform defined CXL ranges.\n");
		return -ENXIO;
	}

	return 0;
}
EXPORT_SYMBOL_NS_GPL(cxl_hdm_decode_init, "CXL");

#define CXL_DOE_TABLE_ACCESS_REQ_CODE		0x000000ff
#define   CXL_DOE_TABLE_ACCESS_REQ_CODE_READ	0
#define CXL_DOE_TABLE_ACCESS_TABLE_TYPE		0x0000ff00
#define   CXL_DOE_TABLE_ACCESS_TABLE_TYPE_CDATA	0
#define CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE	0xffff0000
#define CXL_DOE_TABLE_ACCESS_LAST_ENTRY		0xffff
#define CXL_DOE_PROTOCOL_TABLE_ACCESS 2

#define CDAT_DOE_REQ(entry_handle) cpu_to_le32				\
	(FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE,			\
		    CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) |		\
	 FIELD_PREP(CXL_DOE_TABLE_ACCESS_TABLE_TYPE,			\
		    CXL_DOE_TABLE_ACCESS_TABLE_TYPE_CDATA) |		\
	 FIELD_PREP(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE, (entry_handle)))

static int cxl_cdat_get_length(struct device *dev,
			       struct pci_doe_mb *doe_mb,
			       size_t *length)
{
	__le32 request = CDAT_DOE_REQ(0);
	__le32 response[2];
	int rc;

	rc = pci_doe(doe_mb, PCI_VENDOR_ID_CXL,
		     CXL_DOE_PROTOCOL_TABLE_ACCESS,
		     &request, sizeof(request),
		     &response, sizeof(response));
	if (rc < 0) {
		dev_err(dev, "DOE failed: %d", rc);
		return rc;
	}
	if (rc < sizeof(response))
		return -EIO;

	*length = le32_to_cpu(response[1]);
	dev_dbg(dev, "CDAT length %zu\n", *length);

	return 0;
}

static int cxl_cdat_read_table(struct device *dev,
			       struct pci_doe_mb *doe_mb,
			       struct cdat_doe_rsp *rsp, size_t *length)
{
	size_t received, remaining = *length;
	unsigned int entry_handle = 0;
	union cdat_data *data;
	__le32 saved_dw = 0;

	do {
		__le32 request = CDAT_DOE_REQ(entry_handle);
		int rc;

		rc = pci_doe(doe_mb, PCI_VENDOR_ID_CXL,
			     CXL_DOE_PROTOCOL_TABLE_ACCESS,
			     &request, sizeof(request),
			     rsp, sizeof(*rsp) + remaining);
		if (rc < 0) {
			dev_err(dev, "DOE failed: %d", rc);
			return rc;
		}

		if (rc < sizeof(*rsp))
			return -EIO;

		data = (union cdat_data *)rsp->data;
		received = rc - sizeof(*rsp);

		if (entry_handle == 0) {
			if (received != sizeof(data->header))
				return -EIO;
		} else {
			if (received < sizeof(data->entry) ||
			    received != le16_to_cpu(data->entry.length))
				return -EIO;
		}

		/* Get the CXL table access header entry handle */
		entry_handle = FIELD_GET(CXL_DOE_TABLE_ACCESS_ENTRY_HANDLE,
					 le32_to_cpu(rsp->doe_header));

		/*
		 * Table Access Response Header overwrote the last DW of
		 * previous entry, so restore that DW
		 */
		rsp->doe_header = saved_dw;
		remaining -= received;
		rsp = (void *)rsp + received;
		saved_dw = rsp->doe_header;
	} while (entry_handle != CXL_DOE_TABLE_ACCESS_LAST_ENTRY);

	/* Length in CDAT header may exceed concatenation of CDAT entries */
	*length -= remaining;

	return 0;
}

static unsigned char cdat_checksum(void *buf, size_t size)
{
	unsigned char sum, *data = buf;
	size_t i;

	for (sum = 0, i = 0; i < size; i++)
		sum += data[i];
	return sum;
}

/**
 * read_cdat_data - Read the CDAT data on this port
 * @port: Port to read data from
 *
 * This call will sleep waiting for responses from the DOE mailbox.
 */
void read_cdat_data(struct cxl_port *port)
{
	struct device *uport = port->uport_dev;
	struct device *dev = &port->dev;
	struct pci_doe_mb *doe_mb;
	struct pci_dev *pdev = NULL;
	struct cxl_memdev *cxlmd;
	struct cdat_doe_rsp *buf;
	size_t table_length, length;
	int rc;

	if (is_cxl_memdev(uport)) {
		struct device *host;

		cxlmd = to_cxl_memdev(uport);
		host = cxlmd->dev.parent;
		if (dev_is_pci(host))
			pdev = to_pci_dev(host);
	} else if (dev_is_pci(uport)) {
		pdev = to_pci_dev(uport);
	}

	if (!pdev)
		return;

	doe_mb = pci_find_doe_mailbox(pdev, PCI_VENDOR_ID_CXL,
				      CXL_DOE_PROTOCOL_TABLE_ACCESS);
	if (!doe_mb) {
		dev_dbg(dev, "No CDAT mailbox\n");
		return;
	}

	port->cdat_available = true;

	if (cxl_cdat_get_length(dev, doe_mb, &length)) {
		dev_dbg(dev, "No CDAT length\n");
		return;
	}

	/*
	 * The begin of the CDAT buffer needs space for additional 4
	 * bytes for the DOE header. Table data starts afterwards.
	 */
	buf = devm_kzalloc(dev, sizeof(*buf) + length, GFP_KERNEL);
	if (!buf)
		goto err;

	table_length = length;

	rc = cxl_cdat_read_table(dev, doe_mb, buf, &length);
	if (rc)
		goto err;

	if (table_length != length)
		dev_warn(dev, "Malformed CDAT table length (%zu:%zu), discarding trailing data\n",
			table_length, length);

	if (cdat_checksum(buf->data, length))
		goto err;

	port->cdat.table = buf->data;
	port->cdat.length = length;

	return;
err:
	/* Don't leave table data allocated on error */
	devm_kfree(dev, buf);
	dev_err(dev, "Failed to read/validate CDAT.\n");
}
EXPORT_SYMBOL_NS_GPL(read_cdat_data, "CXL");

static int cxl_flit_size(struct pci_dev *pdev)
{
	if (cxl_pci_flit_256(pdev))
		return 256;

	return 68;
}

/**
 * cxl_pci_get_latency - calculate the link latency for the PCIe link
 * @pdev: PCI device
 *
 * return: calculated latency or 0 for no latency
 *
 * CXL Memory Device SW Guide v1.0 2.11.4 Link latency calculation
 * Link latency = LinkPropagationLatency + FlitLatency + RetimerLatency
 * LinkProgationLatency is negligible, so 0 will be used
 * RetimerLatency is assumed to be negligible and 0 will be used
 * FlitLatency = FlitSize / LinkBandwidth
 * FlitSize is defined by spec. CXL rev3.0 4.2.1.
 * 68B flit is used up to 32GT/s. >32GT/s, 256B flit size is used.
 * The FlitLatency is converted to picoseconds.
 */
long cxl_pci_get_latency(struct pci_dev *pdev)
{
	long bw;

	bw = pcie_link_speed_mbps(pdev);
	if (bw < 0)
		return 0;
	bw /= BITS_PER_BYTE;

	return cxl_flit_size(pdev) * MEGA / bw;
}

static int __cxl_endpoint_decoder_reset_detected(struct device *dev, void *data)
{
	struct cxl_port *port = data;
	struct cxl_decoder *cxld;
	struct cxl_hdm *cxlhdm;
	void __iomem *hdm;
	u32 ctrl;

	if (!is_endpoint_decoder(dev))
		return 0;

	cxld = to_cxl_decoder(dev);
	if ((cxld->flags & CXL_DECODER_F_ENABLE) == 0)
		return 0;

	cxlhdm = dev_get_drvdata(&port->dev);
	hdm = cxlhdm->regs.hdm_decoder;
	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));

	return !FIELD_GET(CXL_HDM_DECODER0_CTRL_COMMITTED, ctrl);
}

bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port)
{
	return device_for_each_child(&port->dev, port,
				     __cxl_endpoint_decoder_reset_detected);
}
EXPORT_SYMBOL_NS_GPL(cxl_endpoint_decoder_reset_detected, "CXL");

int cxl_pci_get_bandwidth(struct pci_dev *pdev, struct access_coordinate *c)
{
	int speed, bw;
	u16 lnksta;
	u32 width;

	speed = pcie_link_speed_mbps(pdev);
	if (speed < 0)
		return speed;
	speed /= BITS_PER_BYTE;

	pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta);
	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, lnksta);
	bw = speed * width;

	for (int i = 0; i < ACCESS_COORDINATE_MAX; i++) {
		c[i].read_bandwidth = bw;
		c[i].write_bandwidth = bw;
	}

	return 0;
}

/*
 * Set max timeout such that platforms will optimize GPF flow to avoid
 * the implied worst-case scenario delays. On a sane platform, all
 * devices should always complete GPF within the energy budget of
 * the GPF flow. The kernel does not have enough information to pick
 * anything better than "maximize timeouts and hope it works".
 *
 * A misbehaving device could block forward progress of GPF for all
 * the other devices, exhausting the energy budget of the platform.
 * However, the spec seems to assume that moving on from slow to respond
 * devices is a virtue. It is not possible to know that, in actuality,
 * the slow to respond device is *the* most critical device in the
 * system to wait.
 */
#define GPF_TIMEOUT_BASE_MAX 2
#define GPF_TIMEOUT_SCALE_MAX 7 /* 10 seconds */

u16 cxl_gpf_get_dvsec(struct device *dev)
{
	struct pci_dev *pdev;
	bool is_port = true;
	u16 dvsec;

	if (!dev_is_pci(dev))
		return 0;

	pdev = to_pci_dev(dev);
	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ENDPOINT)
		is_port = false;

	dvsec = pci_find_dvsec_capability(pdev, PCI_VENDOR_ID_CXL,
			is_port ? PCI_DVSEC_CXL_PORT_GPF : PCI_DVSEC_CXL_DEVICE_GPF);
	if (!dvsec)
		dev_warn(dev, "%s GPF DVSEC not present\n",
			 is_port ? "Port" : "Device");
	return dvsec;
}
EXPORT_SYMBOL_NS_GPL(cxl_gpf_get_dvsec, "CXL");

static int update_gpf_port_dvsec(struct pci_dev *pdev, int dvsec, int phase)
{
	u64 base, scale;
	int rc, offset;
	u16 ctrl;

	switch (phase) {
	case 1:
		offset = PCI_DVSEC_CXL_PORT_GPF_PHASE_1_CONTROL;
		base = PCI_DVSEC_CXL_PORT_GPF_PHASE_1_TMO_BASE;
		scale = PCI_DVSEC_CXL_PORT_GPF_PHASE_1_TMO_SCALE;
		break;
	case 2:
		offset = PCI_DVSEC_CXL_PORT_GPF_PHASE_2_CONTROL;
		base = PCI_DVSEC_CXL_PORT_GPF_PHASE_2_TMO_BASE;
		scale = PCI_DVSEC_CXL_PORT_GPF_PHASE_2_TMO_SCALE;
		break;
	default:
		return -EINVAL;
	}

	rc = pci_read_config_word(pdev, dvsec + offset, &ctrl);
	if (rc)
		return rc;

	if (FIELD_GET(base, ctrl) == GPF_TIMEOUT_BASE_MAX &&
	    FIELD_GET(scale, ctrl) == GPF_TIMEOUT_SCALE_MAX)
		return 0;

	ctrl = FIELD_PREP(base, GPF_TIMEOUT_BASE_MAX);
	ctrl |= FIELD_PREP(scale, GPF_TIMEOUT_SCALE_MAX);

	rc = pci_write_config_word(pdev, dvsec + offset, ctrl);
	if (!rc)
		pci_dbg(pdev, "Port GPF phase %d timeout: %d0 secs\n",
			phase, GPF_TIMEOUT_BASE_MAX);

	return rc;
}

int cxl_gpf_port_setup(struct cxl_dport *dport)
{
	if (!dport)
		return -EINVAL;

	if (!dport->gpf_dvsec) {
		struct pci_dev *pdev;
		int dvsec;

		dvsec = cxl_gpf_get_dvsec(dport->dport_dev);
		if (!dvsec)
			return -EINVAL;

		dport->gpf_dvsec = dvsec;
		pdev = to_pci_dev(dport->dport_dev);
		update_gpf_port_dvsec(pdev, dport->gpf_dvsec, 1);
		update_gpf_port_dvsec(pdev, dport->gpf_dvsec, 2);
	}

	return 0;
}

struct cxl_walk_context {
	struct pci_bus *bus;
	struct cxl_port *port;
	int type;
	int error;
	int count;
};

static int count_dports(struct pci_dev *pdev, void *data)
{
	struct cxl_walk_context *ctx = data;
	int type = pci_pcie_type(pdev);

	if (pdev->bus != ctx->bus)
		return 0;
	if (!pci_is_pcie(pdev))
		return 0;
	if (type != ctx->type)
		return 0;

	ctx->count++;
	return 0;
}

int cxl_port_get_possible_dports(struct cxl_port *port)
{
	struct pci_bus *bus = cxl_port_to_pci_bus(port);
	struct cxl_walk_context ctx;
	int type;

	if (!bus) {
		dev_err(&port->dev, "No PCI bus found for port %s\n",
			dev_name(&port->dev));
		return -ENXIO;
	}

	if (pci_is_root_bus(bus))
		type = PCI_EXP_TYPE_ROOT_PORT;
	else
		type = PCI_EXP_TYPE_DOWNSTREAM;

	ctx = (struct cxl_walk_context) {
		.bus = bus,
		.type = type,
	};
	pci_walk_bus(bus, count_dports, &ctx);

	return ctx.count;
}