Fixed MTP to work with TWRP

drivers/pci/pcie/aspm.c

@@ -0,0 +1,991 @@
+/*
+ * 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 */
+
+#ifdef CONFIG_PCIEASPM_PERFORMANCE
+static int aspm_policy = POLICY_PERFORMANCE;
+#elif defined CONFIG_PCIEASPM_POWERSAVE
+static int aspm_policy = POLICY_POWERSAVE;
+#else
+static int aspm_policy;
+#endif
+
+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)
+{
+	struct pci_dev *child;
+	struct pci_bus *linkbus = link->pdev->subordinate;
+
+	list_for_each_entry(child, &linkbus->devices, bus_list) {
+		if (enable)
+			pcie_capability_set_word(child, PCI_EXP_LNKCTL,
+						 PCI_EXP_LNKCTL_CLKREQ_EN);
+		else
+			pcie_capability_clear_word(child, PCI_EXP_LNKCTL,
+						   PCI_EXP_LNKCTL_CLKREQ_EN);
+	}
+	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 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) {
+		pcie_capability_read_dword(child, PCI_EXP_LNKCAP, &reg32);
+		if (!(reg32 & PCI_EXP_LNKCAP_CLKPM)) {
+			capable = 0;
+			enabled = 0;
+			break;
+		}
+		pcie_capability_read_word(child, 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 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 */
+	pcie_capability_read_word(child, PCI_EXP_LNKSTA, &reg16);
+	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
+		same_clock = 0;
+
+	/* Check upstream component if bit Slot Clock Configuration is 1 */
+	pcie_capability_read_word(parent, 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) {
+		pcie_capability_read_word(child, 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;
+		pcie_capability_write_word(child, PCI_EXP_LNKCTL, reg16);
+	}
+
+	/* Configure upstream component */
+	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
+	parent_reg = reg16;
+	if (same_clock)
+		reg16 |= PCI_EXP_LNKCTL_CCC;
+	else
+		reg16 &= ~PCI_EXP_LNKCTL_CCC;
+	pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
+
+	/* Retrain link */
+	reg16 |= PCI_EXP_LNKCTL_RL;
+	pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
+
+	/* Wait for link training end. Break out after waiting for timeout */
+	start_jiffies = jiffies;
+	for (;;) {
+		pcie_capability_read_word(parent, 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_err(&parent->dev, "ASPM: Could not configure common clock\n");
+	list_for_each_entry(child, &linkbus->devices, bus_list)
+		pcie_capability_write_word(child, PCI_EXP_LNKCTL,
+					   child_reg[PCI_FUNC(child->devfn)]);
+	pcie_capability_write_word(parent, 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)
+{
+	u16 reg16;
+	u32 reg32;
+
+	pcie_capability_read_dword(pdev, 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;
+	pcie_capability_read_word(pdev, 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 (pci_pcie_type(child) == 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) {
+		u32 reg32, encoding;
+		struct aspm_latency *acceptable =
+			&link->acceptable[PCI_FUNC(child->devfn)];
+
+		if (pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT &&
+		    pci_pcie_type(child) != PCI_EXP_TYPE_LEG_END)
+			continue;
+
+		pcie_capability_read_dword(child, 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)
+{
+	pcie_capability_clear_and_set_word(pdev, PCI_EXP_LNKCTL,
+					   PCI_EXP_LNKCTL_ASPMC, val);
+}
+
+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 |= PCI_EXP_LNKCTL_ASPM_L0S;
+	if (state & ASPM_STATE_L0S_DW)
+		upstream |= PCI_EXP_LNKCTL_ASPM_L0S;
+	if (state & ASPM_STATE_L1) {
+		upstream |= PCI_EXP_LNKCTL_ASPM_L1;
+		dwstream |= PCI_EXP_LNKCTL_ASPM_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;
+	u32 reg32;
+
+	/*
+	 * 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) {
+		if (!pci_is_pcie(child))
+			return -EINVAL;
+
+		/*
+		 * If ASPM is disabled then we're not going to change
+		 * the BIOS state. It's safe to continue even if it's a
+		 * pre-1.1 device
+		 */
+
+		if (aspm_disabled)
+			continue;
+
+		/*
+		 * 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
+		 */
+		pcie_capability_read_dword(child, PCI_EXP_DEVCAP, &reg32);
+		if (!(reg32 & PCI_EXP_DEVCAP_RBER) && !aspm_force) {
+			dev_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 (pci_pcie_type(pdev) == 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 scanned.
+ * @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 (!aspm_support_enabled)
+		return;
+
+	if (!pci_is_pcie(pdev) || pdev->link_state)
+		return;
+	if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT &&
+	    pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM)
+		return;
+
+	/* VIA has a strange chipset, root port is under a bridge */
+	if (pci_pcie_type(pdev) == 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 ((pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT) &&
+			    (pci_pcie_type(child) != 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 (!parent || !parent->link_state)
+		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 ((pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) &&
+	    (pci_pcie_type(pdev) != 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 ((pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) &&
+	    (pci_pcie_type(pdev) != 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);
+}
+
+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 (!pci_is_pcie(pdev))
+		return;
+
+	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT ||
+	    pci_pcie_type(pdev) == PCI_EXP_TYPE_DOWNSTREAM)
+		parent = pdev;
+	if (!parent || !parent->link_state)
+		return;
+
+	/*
+	 * A driver requested that ASPM be disabled on this device, but
+	 * if we don't have permission to manage ASPM (e.g., on ACPI
+	 * systems we have to observe the FADT ACPI_FADT_NO_ASPM bit and
+	 * the _OSC method), we can't honor that request.  Windows has
+	 * a similar mechanism using "PciASPMOptOut", which is also
+	 * ignored in this situation.
+	 */
+	if (aspm_disabled && !force) {
+		dev_warn(&pdev->dev, "can't disable ASPM; OS doesn't have ASPM control\n");
+		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);
+
+/**
+ * pci_disable_link_state - Disable device's link state, so the link will
+ * never enter specific states.  Note that if the BIOS didn't grant ASPM
+ * control to the OS, this does nothing because we can't touch the LNKCTL
+ * register.
+ *
+ * @pdev: PCI device
+ * @state: ASPM link state to disable
+ */
+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;
+
+	if (aspm_force)
+		return;
+
+	/*
+	 * 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) ||
+	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT &&
+	     pci_pcie_type(pdev) != 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) ||
+	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT &&
+	     pci_pcie_type(pdev) != 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;
+	}
+}
+
+bool pcie_aspm_support_enabled(void)
+{
+	return aspm_support_enabled;
+}
+EXPORT_SYMBOL(pcie_aspm_support_enabled);