source: src/linux/universal/linux-3.2/drivers/pci/pcie/aspm.c @ 18761

/*
 * File:        drivers/pci/pcie/aspm.c
 * Enabling PCIe link L0s/L1 state and Clock Power Management
 *
 * Copyright (C) 2007 Intel
 * Copyright (C) Zhang Yanmin (yanmin.zhang@intel.com)
 * Copyright (C) Shaohua Li (shaohua.li@intel.com)
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/pci.h>
#include <linux/pci_regs.h>
#include <linux/errno.h>
#include <linux/pm.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/delay.h>
#include <linux/pci-aspm.h>
#include "../pci.h"

#ifdef MODULE_PARAM_PREFIX
#undef MODULE_PARAM_PREFIX
#endif
#define MODULE_PARAM_PREFIX "pcie_aspm."

/* Note: those are not register definitions */
#define ASPM_STATE_L0S_UP       (1)     /* Upstream direction L0s state */
#define ASPM_STATE_L0S_DW       (2)     /* Downstream direction L0s state */
#define ASPM_STATE_L1           (4)     /* L1 state */
#define ASPM_STATE_L0S          (ASPM_STATE_L0S_UP | ASPM_STATE_L0S_DW)
#define ASPM_STATE_ALL          (ASPM_STATE_L0S | ASPM_STATE_L1)

struct aspm_latency {
        u32 l0s;                        /* L0s latency (nsec) */
        u32 l1;                         /* L1 latency (nsec) */
};

struct pcie_link_state {
        struct pci_dev *pdev;           /* Upstream component of the Link */
        struct pcie_link_state *root;   /* pointer to the root port link */
        struct pcie_link_state *parent; /* pointer to the parent Link state */
        struct list_head sibling;       /* node in link_list */
        struct list_head children;      /* list of child link states */
        struct list_head link;          /* node in parent's children list */

        /* ASPM state */
        u32 aspm_support:3;             /* Supported ASPM state */
        u32 aspm_enabled:3;             /* Enabled ASPM state */
        u32 aspm_capable:3;             /* Capable ASPM state with latency */
        u32 aspm_default:3;             /* Default ASPM state by BIOS */
        u32 aspm_disable:3;             /* Disabled ASPM state */

        /* Clock PM state */
        u32 clkpm_capable:1;            /* Clock PM capable? */
        u32 clkpm_enabled:1;            /* Current Clock PM state */
        u32 clkpm_default:1;            /* Default Clock PM state by BIOS */

        /* Exit latencies */
        struct aspm_latency latency_up; /* Upstream direction exit latency */
        struct aspm_latency latency_dw; /* Downstream direction exit latency */
        /*
         * Endpoint acceptable latencies. A pcie downstream port only
         * has one slot under it, so at most there are 8 functions.
         */
        struct aspm_latency acceptable[8];
};

static int aspm_disabled, aspm_force;
static bool aspm_support_enabled = true;
static DEFINE_MUTEX(aspm_lock);
static LIST_HEAD(link_list);

#define POLICY_DEFAULT 0        /* BIOS default setting */
#define POLICY_PERFORMANCE 1    /* high performance */
#define POLICY_POWERSAVE 2      /* high power saving */
static int aspm_policy;
static const char *policy_str[] = {
        [POLICY_DEFAULT] = "default",
        [POLICY_PERFORMANCE] = "performance",
        [POLICY_POWERSAVE] = "powersave"
};

#define LINK_RETRAIN_TIMEOUT HZ

static int policy_to_aspm_state(struct pcie_link_state *link)
{
        switch (aspm_policy) {
        case POLICY_PERFORMANCE:
                /* Disable ASPM and Clock PM */
                return 0;
        case POLICY_POWERSAVE:
                /* Enable ASPM L0s/L1 */
                return ASPM_STATE_ALL;
        case POLICY_DEFAULT:
                return link->aspm_default;
        }
        return 0;
}

static int policy_to_clkpm_state(struct pcie_link_state *link)
{
        switch (aspm_policy) {
        case POLICY_PERFORMANCE:
                /* Disable ASPM and Clock PM */
                return 0;
        case POLICY_POWERSAVE:
                /* Disable Clock PM */
                return 1;
        case POLICY_DEFAULT:
                return link->clkpm_default;
        }
        return 0;
}

static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
{
        int pos;
        u16 reg16;
        struct pci_dev *child;
        struct pci_bus *linkbus = link->pdev->subordinate;

        list_for_each_entry(child, &linkbus->devices, bus_list) {
                pos = pci_pcie_cap(child);
                if (!pos)
                        return;
                pci_read_config_word(child, pos + PCI_EXP_LNKCTL, &reg16);
                if (enable)
                        reg16 |= PCI_EXP_LNKCTL_CLKREQ_EN;
                else
                        reg16 &= ~PCI_EXP_LNKCTL_CLKREQ_EN;
                pci_write_config_word(child, pos + PCI_EXP_LNKCTL, reg16);
        }
        link->clkpm_enabled = !!enable;
}

static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
{
        /* Don't enable Clock PM if the link is not Clock PM capable */
        if (!link->clkpm_capable && enable)
                enable = 0;
        /* Need nothing if the specified equals to current state */
        if (link->clkpm_enabled == enable)
                return;
        pcie_set_clkpm_nocheck(link, enable);
}

static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
{
        int pos, capable = 1, enabled = 1;
        u32 reg32;
        u16 reg16;
        struct pci_dev *child;
        struct pci_bus *linkbus = link->pdev->subordinate;

        /* All functions should have the same cap and state, take the worst */
        list_for_each_entry(child, &linkbus->devices, bus_list) {
                pos = pci_pcie_cap(child);
                if (!pos)
                        return;
                pci_read_config_dword(child, pos + PCI_EXP_LNKCAP, &reg32);
                if (!(reg32 & PCI_EXP_LNKCAP_CLKPM)) {
                        capable = 0;
                        enabled = 0;
                        break;
                }
                pci_read_config_word(child, pos + PCI_EXP_LNKCTL, &reg16);
                if (!(reg16 & PCI_EXP_LNKCTL_CLKREQ_EN))
                        enabled = 0;
        }
        link->clkpm_enabled = enabled;
        link->clkpm_default = enabled;
        link->clkpm_capable = (blacklist) ? 0 : capable;
}

/*
 * pcie_aspm_configure_common_clock: check if the 2 ends of a link
 *   could use common clock. If they are, configure them to use the
 *   common clock. That will reduce the ASPM state exit latency.
 */
static void pcie_aspm_configure_common_clock(struct pcie_link_state *link)
{
        int ppos, cpos, same_clock = 1;
        u16 reg16, parent_reg, child_reg[8];
        unsigned long start_jiffies;
        struct pci_dev *child, *parent = link->pdev;
        struct pci_bus *linkbus = parent->subordinate;
        /*
         * All functions of a slot should have the same Slot Clock
         * Configuration, so just check one function
         */
        child = list_entry(linkbus->devices.next, struct pci_dev, bus_list);
        BUG_ON(!pci_is_pcie(child));

        /* Check downstream component if bit Slot Clock Configuration is 1 */
        cpos = pci_pcie_cap(child);
        pci_read_config_word(child, cpos + PCI_EXP_LNKSTA, &reg16);
        if (!(reg16 & PCI_EXP_LNKSTA_SLC))
                same_clock = 0;

        /* Check upstream component if bit Slot Clock Configuration is 1 */
        ppos = pci_pcie_cap(parent);
        pci_read_config_word(parent, ppos + PCI_EXP_LNKSTA, &reg16);
        if (!(reg16 & PCI_EXP_LNKSTA_SLC))
                same_clock = 0;

        /* Configure downstream component, all functions */
        list_for_each_entry(child, &linkbus->devices, bus_list) {
                cpos = pci_pcie_cap(child);
                pci_read_config_word(child, cpos + PCI_EXP_LNKCTL, &reg16);
                child_reg[PCI_FUNC(child->devfn)] = reg16;
                if (same_clock)
                        reg16 |= PCI_EXP_LNKCTL_CCC;
                else
                        reg16 &= ~PCI_EXP_LNKCTL_CCC;
                pci_write_config_word(child, cpos + PCI_EXP_LNKCTL, reg16);
        }

        /* Configure upstream component */
        pci_read_config_word(parent, ppos + PCI_EXP_LNKCTL, &reg16);
        parent_reg = reg16;
        if (same_clock)
                reg16 |= PCI_EXP_LNKCTL_CCC;
        else
                reg16 &= ~PCI_EXP_LNKCTL_CCC;
        pci_write_config_word(parent, ppos + PCI_EXP_LNKCTL, reg16);

        /* Retrain link */
        reg16 |= PCI_EXP_LNKCTL_RL;
        pci_write_config_word(parent, ppos + PCI_EXP_LNKCTL, reg16);

        /* Wait for link training end. Break out after waiting for timeout */
        start_jiffies = jiffies;
        for (;;) {
                pci_read_config_word(parent, ppos + PCI_EXP_LNKSTA, &reg16);
                if (!(reg16 & PCI_EXP_LNKSTA_LT))
                        break;
                if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT))
                        break;
                msleep(1);
        }
        if (!(reg16 & PCI_EXP_LNKSTA_LT))
                return;

        /* Training failed. Restore common clock configurations */
        dev_printk(KERN_ERR, &parent->dev,
                   "ASPM: Could not configure common clock\n");
        list_for_each_entry(child, &linkbus->devices, bus_list) {
                cpos = pci_pcie_cap(child);
                pci_write_config_word(child, cpos + PCI_EXP_LNKCTL,
                                      child_reg[PCI_FUNC(child->devfn)]);
        }
        pci_write_config_word(parent, ppos + PCI_EXP_LNKCTL, parent_reg);
}

/* Convert L0s latency encoding to ns */
static u32 calc_l0s_latency(u32 encoding)
{
        if (encoding == 0x7)
                return (5 * 1000);      /* > 4us */
        return (64 << encoding);
}

/* Convert L0s acceptable latency encoding to ns */
static u32 calc_l0s_acceptable(u32 encoding)
{
        if (encoding == 0x7)
                return -1U;
        return (64 << encoding);
}

/* Convert L1 latency encoding to ns */
static u32 calc_l1_latency(u32 encoding)
{
        if (encoding == 0x7)
                return (65 * 1000);     /* > 64us */
        return (1000 << encoding);
}

/* Convert L1 acceptable latency encoding to ns */
static u32 calc_l1_acceptable(u32 encoding)
{
        if (encoding == 0x7)
                return -1U;
        return (1000 << encoding);
}

struct aspm_register_info {
        u32 support:2;
        u32 enabled:2;
        u32 latency_encoding_l0s;
        u32 latency_encoding_l1;
};

static void pcie_get_aspm_reg(struct pci_dev *pdev,
                              struct aspm_register_info *info)
{
        int pos;
        u16 reg16;
        u32 reg32;

        pos = pci_pcie_cap(pdev);
        pci_read_config_dword(pdev, pos + PCI_EXP_LNKCAP, &reg32);
        info->support = (reg32 & PCI_EXP_LNKCAP_ASPMS) >> 10;
        info->latency_encoding_l0s = (reg32 & PCI_EXP_LNKCAP_L0SEL) >> 12;
        info->latency_encoding_l1  = (reg32 & PCI_EXP_LNKCAP_L1EL) >> 15;
        pci_read_config_word(pdev, pos + PCI_EXP_LNKCTL, &reg16);
        info->enabled = reg16 & PCI_EXP_LNKCTL_ASPMC;
}

static void pcie_aspm_check_latency(struct pci_dev *endpoint)
{
        u32 latency, l1_switch_latency = 0;
        struct aspm_latency *acceptable;
        struct pcie_link_state *link;

        /* Device not in D0 doesn't need latency check */
        if ((endpoint->current_state != PCI_D0) &&
            (endpoint->current_state != PCI_UNKNOWN))
                return;

        link = endpoint->bus->self->link_state;
        acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];

        while (link) {
                /* Check upstream direction L0s latency */
                if ((link->aspm_capable & ASPM_STATE_L0S_UP) &&
                    (link->latency_up.l0s > acceptable->l0s))
                        link->aspm_capable &= ~ASPM_STATE_L0S_UP;

                /* Check downstream direction L0s latency */
                if ((link->aspm_capable & ASPM_STATE_L0S_DW) &&
                    (link->latency_dw.l0s > acceptable->l0s))
                        link->aspm_capable &= ~ASPM_STATE_L0S_DW;
                /*
                 * Check L1 latency.
                 * Every switch on the path to root complex need 1
                 * more microsecond for L1. Spec doesn't mention L0s.
                 */
                latency = max_t(u32, link->latency_up.l1, link->latency_dw.l1);
                if ((link->aspm_capable & ASPM_STATE_L1) &&
                    (latency + l1_switch_latency > acceptable->l1))
                        link->aspm_capable &= ~ASPM_STATE_L1;
                l1_switch_latency += 1000;

                link = link->parent;
        }
}

static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
{
        struct pci_dev *child, *parent = link->pdev;
        struct pci_bus *linkbus = parent->subordinate;
        struct aspm_register_info upreg, dwreg;

        if (blacklist) {
                /* Set enabled/disable so that we will disable ASPM later */
                link->aspm_enabled = ASPM_STATE_ALL;
                link->aspm_disable = ASPM_STATE_ALL;
                return;
        }

        /* Configure common clock before checking latencies */
        pcie_aspm_configure_common_clock(link);

        /* Get upstream/downstream components' register state */
        pcie_get_aspm_reg(parent, &upreg);
        child = list_entry(linkbus->devices.next, struct pci_dev, bus_list);
        pcie_get_aspm_reg(child, &dwreg);

        /*
         * Setup L0s state
         *
         * Note that we must not enable L0s in either direction on a
         * given link unless components on both sides of the link each
         * support L0s.
         */
        if (dwreg.support & upreg.support & PCIE_LINK_STATE_L0S)
                link->aspm_support |= ASPM_STATE_L0S;
        if (dwreg.enabled & PCIE_LINK_STATE_L0S)
                link->aspm_enabled |= ASPM_STATE_L0S_UP;
        if (upreg.enabled & PCIE_LINK_STATE_L0S)
                link->aspm_enabled |= ASPM_STATE_L0S_DW;
        link->latency_up.l0s = calc_l0s_latency(upreg.latency_encoding_l0s);
        link->latency_dw.l0s = calc_l0s_latency(dwreg.latency_encoding_l0s);

        /* Setup L1 state */
        if (upreg.support & dwreg.support & PCIE_LINK_STATE_L1)
                link->aspm_support |= ASPM_STATE_L1;
        if (upreg.enabled & dwreg.enabled & PCIE_LINK_STATE_L1)
                link->aspm_enabled |= ASPM_STATE_L1;
        link->latency_up.l1 = calc_l1_latency(upreg.latency_encoding_l1);
        link->latency_dw.l1 = calc_l1_latency(dwreg.latency_encoding_l1);

        /* Save default state */
        link->aspm_default = link->aspm_enabled;

        /* Setup initial capable state. Will be updated later */
        link->aspm_capable = link->aspm_support;
        /*
         * If the downstream component has pci bridge function, don't
         * do ASPM for now.
         */
        list_for_each_entry(child, &linkbus->devices, bus_list) {
                if (child->pcie_type == PCI_EXP_TYPE_PCI_BRIDGE) {
                        link->aspm_disable = ASPM_STATE_ALL;
                        break;
                }
        }

        /* Get and check endpoint acceptable latencies */
        list_for_each_entry(child, &linkbus->devices, bus_list) {
                int pos;
                u32 reg32, encoding;
                struct aspm_latency *acceptable =
                        &link->acceptable[PCI_FUNC(child->devfn)];

                if (child->pcie_type != PCI_EXP_TYPE_ENDPOINT &&
                    child->pcie_type != PCI_EXP_TYPE_LEG_END)
                        continue;

                pos = pci_pcie_cap(child);
                pci_read_config_dword(child, pos + PCI_EXP_DEVCAP, &reg32);
                /* Calculate endpoint L0s acceptable latency */
                encoding = (reg32 & PCI_EXP_DEVCAP_L0S) >> 6;
                acceptable->l0s = calc_l0s_acceptable(encoding);
                /* Calculate endpoint L1 acceptable latency */
                encoding = (reg32 & PCI_EXP_DEVCAP_L1) >> 9;
                acceptable->l1 = calc_l1_acceptable(encoding);

                pcie_aspm_check_latency(child);
        }
}

static void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
{
        u16 reg16;
        int pos = pci_pcie_cap(pdev);

        pci_read_config_word(pdev, pos + PCI_EXP_LNKCTL, &reg16);
        reg16 &= ~0x3;
        reg16 |= val;
        pci_write_config_word(pdev, pos + PCI_EXP_LNKCTL, reg16);
}

static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
{
        u32 upstream = 0, dwstream = 0;
        struct pci_dev *child, *parent = link->pdev;
        struct pci_bus *linkbus = parent->subordinate;

        /* Nothing to do if the link is already in the requested state */
        state &= (link->aspm_capable & ~link->aspm_disable);
        if (link->aspm_enabled == state)
                return;
        /* Convert ASPM state to upstream/downstream ASPM register state */
        if (state & ASPM_STATE_L0S_UP)
                dwstream |= PCIE_LINK_STATE_L0S;
        if (state & ASPM_STATE_L0S_DW)
                upstream |= PCIE_LINK_STATE_L0S;
        if (state & ASPM_STATE_L1) {
                upstream |= PCIE_LINK_STATE_L1;
                dwstream |= PCIE_LINK_STATE_L1;
        }
        /*
         * Spec 2.0 suggests all functions should be configured the
         * same setting for ASPM. Enabling ASPM L1 should be done in
         * upstream component first and then downstream, and vice
         * versa for disabling ASPM L1. Spec doesn't mention L0S.
         */
        if (state & ASPM_STATE_L1)
                pcie_config_aspm_dev(parent, upstream);
        list_for_each_entry(child, &linkbus->devices, bus_list)
                pcie_config_aspm_dev(child, dwstream);
        if (!(state & ASPM_STATE_L1))
                pcie_config_aspm_dev(parent, upstream);

        link->aspm_enabled = state;
}

static void pcie_config_aspm_path(struct pcie_link_state *link)
{
        while (link) {
                pcie_config_aspm_link(link, policy_to_aspm_state(link));
                link = link->parent;
        }
}

static void free_link_state(struct pcie_link_state *link)
{
        link->pdev->link_state = NULL;
        kfree(link);
}

static int pcie_aspm_sanity_check(struct pci_dev *pdev)
{
        struct pci_dev *child;
        int pos;
        u32 reg32;

        if (aspm_disabled)
                return 0;

        /*
         * Some functions in a slot might not all be PCIe functions,
         * very strange. Disable ASPM for the whole slot
         */
        list_for_each_entry(child, &pdev->subordinate->devices, bus_list) {
                pos = pci_pcie_cap(child);
                if (!pos)
                        return -EINVAL;
                /*
                 * Disable ASPM for pre-1.1 PCIe device, we follow MS to use
                 * RBER bit to determine if a function is 1.1 version device
                 */
                pci_read_config_dword(child, pos + PCI_EXP_DEVCAP, &reg32);
                if (!(reg32 & PCI_EXP_DEVCAP_RBER) && !aspm_force) {
                        dev_printk(KERN_INFO, &child->dev, "disabling ASPM"
                                " on pre-1.1 PCIe device.  You can enable it"
                                " with 'pcie_aspm=force'\n");
                        return -EINVAL;
                }
        }
        return 0;
}

static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
{
        struct pcie_link_state *link;

        link = kzalloc(sizeof(*link), GFP_KERNEL);
        if (!link)
                return NULL;
        INIT_LIST_HEAD(&link->sibling);
        INIT_LIST_HEAD(&link->children);
        INIT_LIST_HEAD(&link->link);
        link->pdev = pdev;
        if (pdev->pcie_type == PCI_EXP_TYPE_DOWNSTREAM) {
                struct pcie_link_state *parent;
                parent = pdev->bus->parent->self->link_state;
                if (!parent) {
                        kfree(link);
                        return NULL;
                }
                link->parent = parent;
                list_add(&link->link, &parent->children);
        }
        /* Setup a pointer to the root port link */
        if (!link->parent)
                link->root = link;
        else
                link->root = link->parent->root;

        list_add(&link->sibling, &link_list);
        pdev->link_state = link;
        return link;
}

/*
 * pcie_aspm_init_link_state: Initiate PCI express link state.
 * It is called after the pcie and its children devices are scaned.
 * @pdev: the root port or switch downstream port
 */
void pcie_aspm_init_link_state(struct pci_dev *pdev)
{
        struct pcie_link_state *link;
        int blacklist = !!pcie_aspm_sanity_check(pdev);

        if (!pci_is_pcie(pdev) || pdev->link_state)
                return;
        if (pdev->pcie_type != PCI_EXP_TYPE_ROOT_PORT &&
            pdev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM)
                return;

        /* VIA has a strange chipset, root port is under a bridge */
        if (pdev->pcie_type == PCI_EXP_TYPE_ROOT_PORT &&
            pdev->bus->self)
                return;

        down_read(&pci_bus_sem);
        if (list_empty(&pdev->subordinate->devices))
                goto out;

        mutex_lock(&aspm_lock);
        link = alloc_pcie_link_state(pdev);
        if (!link)
                goto unlock;
        /*
         * Setup initial ASPM state. Note that we need to configure
         * upstream links also because capable state of them can be
         * update through pcie_aspm_cap_init().
         */
        pcie_aspm_cap_init(link, blacklist);

        /* Setup initial Clock PM state */
        pcie_clkpm_cap_init(link, blacklist);

        /*
         * At this stage drivers haven't had an opportunity to change the
         * link policy setting. Enabling ASPM on broken hardware can cripple
         * it even before the driver has had a chance to disable ASPM, so
         * default to a safe level right now. If we're enabling ASPM beyond
         * the BIOS's expectation, we'll do so once pci_enable_device() is
         * called.
         */
        if (aspm_policy != POLICY_POWERSAVE) {
                pcie_config_aspm_path(link);
                pcie_set_clkpm(link, policy_to_clkpm_state(link));
        }

unlock:
        mutex_unlock(&aspm_lock);
out:
        up_read(&pci_bus_sem);
}

/* Recheck latencies and update aspm_capable for links under the root */
static void pcie_update_aspm_capable(struct pcie_link_state *root)
{
        struct pcie_link_state *link;
        BUG_ON(root->parent);
        list_for_each_entry(link, &link_list, sibling) {
                if (link->root != root)
                        continue;
                link->aspm_capable = link->aspm_support;
        }
        list_for_each_entry(link, &link_list, sibling) {
                struct pci_dev *child;
                struct pci_bus *linkbus = link->pdev->subordinate;
                if (link->root != root)
                        continue;
                list_for_each_entry(child, &linkbus->devices, bus_list) {
                        if ((child->pcie_type != PCI_EXP_TYPE_ENDPOINT) &&
                            (child->pcie_type != PCI_EXP_TYPE_LEG_END))
                                continue;
                        pcie_aspm_check_latency(child);
                }
        }
}

/* @pdev: the endpoint device */
void pcie_aspm_exit_link_state(struct pci_dev *pdev)
{
        struct pci_dev *parent = pdev->bus->self;
        struct pcie_link_state *link, *root, *parent_link;

        if (!pci_is_pcie(pdev) || !parent || !parent->link_state)
                return;
        if ((parent->pcie_type != PCI_EXP_TYPE_ROOT_PORT) &&
            (parent->pcie_type != PCI_EXP_TYPE_DOWNSTREAM))
                return;

        down_read(&pci_bus_sem);
        mutex_lock(&aspm_lock);
        /*
         * All PCIe functions are in one slot, remove one function will remove
         * the whole slot, so just wait until we are the last function left.
         */
        if (!list_is_last(&pdev->bus_list, &parent->subordinate->devices))
                goto out;

        link = parent->link_state;
        root = link->root;
        parent_link = link->parent;

        /* All functions are removed, so just disable ASPM for the link */
        pcie_config_aspm_link(link, 0);
        list_del(&link->sibling);
        list_del(&link->link);
        /* Clock PM is for endpoint device */
        free_link_state(link);

        /* Recheck latencies and configure upstream links */
        if (parent_link) {
                pcie_update_aspm_capable(root);
                pcie_config_aspm_path(parent_link);
        }
out:
        mutex_unlock(&aspm_lock);
        up_read(&pci_bus_sem);
}

/* @pdev: the root port or switch downstream port */
void pcie_aspm_pm_state_change(struct pci_dev *pdev)
{
        struct pcie_link_state *link = pdev->link_state;

        if (aspm_disabled || !pci_is_pcie(pdev) || !link)
                return;
        if ((pdev->pcie_type != PCI_EXP_TYPE_ROOT_PORT) &&
            (pdev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM))
                return;
        /*
         * Devices changed PM state, we should recheck if latency
         * meets all functions' requirement
         */
        down_read(&pci_bus_sem);
        mutex_lock(&aspm_lock);
        pcie_update_aspm_capable(link->root);
        pcie_config_aspm_path(link);
        mutex_unlock(&aspm_lock);
        up_read(&pci_bus_sem);
}

void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
{
        struct pcie_link_state *link = pdev->link_state;

        if (aspm_disabled || !pci_is_pcie(pdev) || !link)
                return;

        if (aspm_policy != POLICY_POWERSAVE)
                return;

        if ((pdev->pcie_type != PCI_EXP_TYPE_ROOT_PORT) &&
            (pdev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM))
                return;

        down_read(&pci_bus_sem);
        mutex_lock(&aspm_lock);
        pcie_config_aspm_path(link);
        pcie_set_clkpm(link, policy_to_clkpm_state(link));
        mutex_unlock(&aspm_lock);
        up_read(&pci_bus_sem);
}

/*
 * pci_disable_link_state - disable pci device's link state, so the link will
 * never enter specific states
 */
static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem,
                                     bool force)
{
        struct pci_dev *parent = pdev->bus->self;
        struct pcie_link_state *link;

        if (aspm_disabled && !force)
                return;

        if (!pci_is_pcie(pdev))
                return;

        if (pdev->pcie_type == PCI_EXP_TYPE_ROOT_PORT ||
            pdev->pcie_type == PCI_EXP_TYPE_DOWNSTREAM)
                parent = pdev;
        if (!parent || !parent->link_state)
                return;

        if (sem)
                down_read(&pci_bus_sem);
        mutex_lock(&aspm_lock);
        link = parent->link_state;
        if (state & PCIE_LINK_STATE_L0S)
                link->aspm_disable |= ASPM_STATE_L0S;
        if (state & PCIE_LINK_STATE_L1)
                link->aspm_disable |= ASPM_STATE_L1;
        pcie_config_aspm_link(link, policy_to_aspm_state(link));

        if (state & PCIE_LINK_STATE_CLKPM) {
                link->clkpm_capable = 0;
                pcie_set_clkpm(link, 0);
        }
        mutex_unlock(&aspm_lock);
        if (sem)
                up_read(&pci_bus_sem);
}

void pci_disable_link_state_locked(struct pci_dev *pdev, int state)
{
        __pci_disable_link_state(pdev, state, false, false);
}
EXPORT_SYMBOL(pci_disable_link_state_locked);

void pci_disable_link_state(struct pci_dev *pdev, int state)
{
        __pci_disable_link_state(pdev, state, true, false);
}
EXPORT_SYMBOL(pci_disable_link_state);

void pcie_clear_aspm(struct pci_bus *bus)
{
        struct pci_dev *child;

        /*
         * Clear any ASPM setup that the firmware has carried out on this bus
         */
        list_for_each_entry(child, &bus->devices, bus_list) {
                __pci_disable_link_state(child, PCIE_LINK_STATE_L0S |
                                         PCIE_LINK_STATE_L1 |
                                         PCIE_LINK_STATE_CLKPM,
                                         false, true);
        }
}

static int pcie_aspm_set_policy(const char *val, struct kernel_param *kp)
{
        int i;
        struct pcie_link_state *link;

        if (aspm_disabled)
                return -EPERM;
        for (i = 0; i < ARRAY_SIZE(policy_str); i++)
                if (!strncmp(val, policy_str[i], strlen(policy_str[i])))
                        break;
        if (i >= ARRAY_SIZE(policy_str))
                return -EINVAL;
        if (i == aspm_policy)
                return 0;

        down_read(&pci_bus_sem);
        mutex_lock(&aspm_lock);
        aspm_policy = i;
        list_for_each_entry(link, &link_list, sibling) {
                pcie_config_aspm_link(link, policy_to_aspm_state(link));
                pcie_set_clkpm(link, policy_to_clkpm_state(link));
        }
        mutex_unlock(&aspm_lock);
        up_read(&pci_bus_sem);
        return 0;
}

static int pcie_aspm_get_policy(char *buffer, struct kernel_param *kp)
{
        int i, cnt = 0;
        for (i = 0; i < ARRAY_SIZE(policy_str); i++)
                if (i == aspm_policy)
                        cnt += sprintf(buffer + cnt, "[%s] ", policy_str[i]);
                else
                        cnt += sprintf(buffer + cnt, "%s ", policy_str[i]);
        return cnt;
}

module_param_call(policy, pcie_aspm_set_policy, pcie_aspm_get_policy,
        NULL, 0644);

#ifdef CONFIG_PCIEASPM_DEBUG
static ssize_t link_state_show(struct device *dev,
                struct device_attribute *attr,
                char *buf)
{
        struct pci_dev *pci_device = to_pci_dev(dev);
        struct pcie_link_state *link_state = pci_device->link_state;

        return sprintf(buf, "%d\n", link_state->aspm_enabled);
}

static ssize_t link_state_store(struct device *dev,
                struct device_attribute *attr,
                const char *buf,
                size_t n)
{
        struct pci_dev *pdev = to_pci_dev(dev);
        struct pcie_link_state *link, *root = pdev->link_state->root;
        u32 val = buf[0] - '0', state = 0;

        if (aspm_disabled)
                return -EPERM;
        if (n < 1 || val > 3)
                return -EINVAL;

        /* Convert requested state to ASPM state */
        if (val & PCIE_LINK_STATE_L0S)
                state |= ASPM_STATE_L0S;
        if (val & PCIE_LINK_STATE_L1)
                state |= ASPM_STATE_L1;

        down_read(&pci_bus_sem);
        mutex_lock(&aspm_lock);
        list_for_each_entry(link, &link_list, sibling) {
                if (link->root != root)
                        continue;
                pcie_config_aspm_link(link, state);
        }
        mutex_unlock(&aspm_lock);
        up_read(&pci_bus_sem);
        return n;
}

static ssize_t clk_ctl_show(struct device *dev,
                struct device_attribute *attr,
                char *buf)
{
        struct pci_dev *pci_device = to_pci_dev(dev);
        struct pcie_link_state *link_state = pci_device->link_state;

        return sprintf(buf, "%d\n", link_state->clkpm_enabled);
}

static ssize_t clk_ctl_store(struct device *dev,
                struct device_attribute *attr,
                const char *buf,
                size_t n)
{
        struct pci_dev *pdev = to_pci_dev(dev);
        int state;

        if (n < 1)
                return -EINVAL;
        state = buf[0]-'0';

        down_read(&pci_bus_sem);
        mutex_lock(&aspm_lock);
        pcie_set_clkpm_nocheck(pdev->link_state, !!state);
        mutex_unlock(&aspm_lock);
        up_read(&pci_bus_sem);

        return n;
}

static DEVICE_ATTR(link_state, 0644, link_state_show, link_state_store);
static DEVICE_ATTR(clk_ctl, 0644, clk_ctl_show, clk_ctl_store);

static char power_group[] = "power";
void pcie_aspm_create_sysfs_dev_files(struct pci_dev *pdev)
{
        struct pcie_link_state *link_state = pdev->link_state;

        if (!pci_is_pcie(pdev) ||
            (pdev->pcie_type != PCI_EXP_TYPE_ROOT_PORT &&
             pdev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM) || !link_state)
                return;

        if (link_state->aspm_support)
                sysfs_add_file_to_group(&pdev->dev.kobj,
                        &dev_attr_link_state.attr, power_group);
        if (link_state->clkpm_capable)
                sysfs_add_file_to_group(&pdev->dev.kobj,
                        &dev_attr_clk_ctl.attr, power_group);
}

void pcie_aspm_remove_sysfs_dev_files(struct pci_dev *pdev)
{
        struct pcie_link_state *link_state = pdev->link_state;

        if (!pci_is_pcie(pdev) ||
            (pdev->pcie_type != PCI_EXP_TYPE_ROOT_PORT &&
             pdev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM) || !link_state)
                return;

        if (link_state->aspm_support)
                sysfs_remove_file_from_group(&pdev->dev.kobj,
                        &dev_attr_link_state.attr, power_group);
        if (link_state->clkpm_capable)
                sysfs_remove_file_from_group(&pdev->dev.kobj,
                        &dev_attr_clk_ctl.attr, power_group);
}
#endif

static int __init pcie_aspm_disable(char *str)
{
        if (!strcmp(str, "off")) {
                aspm_policy = POLICY_DEFAULT;
                aspm_disabled = 1;
                aspm_support_enabled = false;
                printk(KERN_INFO "PCIe ASPM is disabled\n");
        } else if (!strcmp(str, "force")) {
                aspm_force = 1;
                printk(KERN_INFO "PCIe ASPM is forcibly enabled\n");
        }
        return 1;
}

__setup("pcie_aspm=", pcie_aspm_disable);

void pcie_no_aspm(void)
{
        /*
         * Disabling ASPM is intended to prevent the kernel from modifying
         * existing hardware state, not to clear existing state. To that end:
         * (a) set policy to POLICY_DEFAULT in order to avoid changing state
         * (b) prevent userspace from changing policy
         */
        if (!aspm_force) {
                aspm_policy = POLICY_DEFAULT;
                aspm_disabled = 1;
        }
}

/**
 * pcie_aspm_enabled - is PCIe ASPM enabled?
 *
 * Returns true if ASPM has not been disabled by the command-line option
 * pcie_aspm=off.
 **/
int pcie_aspm_enabled(void)
{
       return !aspm_disabled;
}
EXPORT_SYMBOL(pcie_aspm_enabled);

bool pcie_aspm_support_enabled(void)
{
        return aspm_support_enabled;
}
EXPORT_SYMBOL(pcie_aspm_support_enabled);