1 // SPDX-License-Identifier: GPL-2.0
3 * Enable PCIe link L0s/L1 state and Clock Power Management
5 * Copyright (C) 2007 Intel
6 * Copyright (C) Zhang Yanmin (yanmin.zhang@intel.com)
7 * Copyright (C) Shaohua Li (shaohua.li@intel.com)
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/moduleparam.h>
13 #include <linux/pci.h>
14 #include <linux/pci_regs.h>
15 #include <linux/errno.h>
17 #include <linux/init.h>
18 #include <linux/slab.h>
19 #include <linux/jiffies.h>
20 #include <linux/delay.h>
23 #ifdef MODULE_PARAM_PREFIX
24 #undef MODULE_PARAM_PREFIX
26 #define MODULE_PARAM_PREFIX "pcie_aspm."
28 /* Note: those are not register definitions */
29 #define ASPM_STATE_L0S_UP (1) /* Upstream direction L0s state */
30 #define ASPM_STATE_L0S_DW (2) /* Downstream direction L0s state */
31 #define ASPM_STATE_L1 (4) /* L1 state */
32 #define ASPM_STATE_L1_1 (8) /* ASPM L1.1 state */
33 #define ASPM_STATE_L1_2 (0x10) /* ASPM L1.2 state */
34 #define ASPM_STATE_L1_1_PCIPM (0x20) /* PCI PM L1.1 state */
35 #define ASPM_STATE_L1_2_PCIPM (0x40) /* PCI PM L1.2 state */
36 #define ASPM_STATE_L1_SS_PCIPM (ASPM_STATE_L1_1_PCIPM | ASPM_STATE_L1_2_PCIPM)
37 #define ASPM_STATE_L1_2_MASK (ASPM_STATE_L1_2 | ASPM_STATE_L1_2_PCIPM)
38 #define ASPM_STATE_L1SS (ASPM_STATE_L1_1 | ASPM_STATE_L1_1_PCIPM |\
40 #define ASPM_STATE_L0S (ASPM_STATE_L0S_UP | ASPM_STATE_L0S_DW)
41 #define ASPM_STATE_ALL (ASPM_STATE_L0S | ASPM_STATE_L1 | \
45 u32 l0s; /* L0s latency (nsec) */
46 u32 l1; /* L1 latency (nsec) */
49 struct pcie_link_state {
50 struct pci_dev *pdev; /* Upstream component of the Link */
51 struct pci_dev *downstream; /* Downstream component, function 0 */
52 struct pcie_link_state *root; /* pointer to the root port link */
53 struct pcie_link_state *parent; /* pointer to the parent Link state */
54 struct list_head sibling; /* node in link_list */
57 u32 aspm_support:7; /* Supported ASPM state */
58 u32 aspm_enabled:7; /* Enabled ASPM state */
59 u32 aspm_capable:7; /* Capable ASPM state with latency */
60 u32 aspm_default:7; /* Default ASPM state by BIOS */
61 u32 aspm_disable:7; /* Disabled ASPM state */
64 u32 clkpm_capable:1; /* Clock PM capable? */
65 u32 clkpm_enabled:1; /* Current Clock PM state */
66 u32 clkpm_default:1; /* Default Clock PM state by BIOS */
67 u32 clkpm_disable:1; /* Clock PM disabled */
70 struct aspm_latency latency_up; /* Upstream direction exit latency */
71 struct aspm_latency latency_dw; /* Downstream direction exit latency */
73 * Endpoint acceptable latencies. A pcie downstream port only
74 * has one slot under it, so at most there are 8 functions.
76 struct aspm_latency acceptable[8];
78 /* L1 PM Substate info */
80 u32 up_cap_ptr; /* L1SS cap ptr in upstream dev */
81 u32 dw_cap_ptr; /* L1SS cap ptr in downstream dev */
82 u32 ctl1; /* value to be programmed in ctl1 */
83 u32 ctl2; /* value to be programmed in ctl2 */
87 static int aspm_disabled, aspm_force;
88 static bool aspm_support_enabled = true;
89 static DEFINE_MUTEX(aspm_lock);
90 static LIST_HEAD(link_list);
92 #define POLICY_DEFAULT 0 /* BIOS default setting */
93 #define POLICY_PERFORMANCE 1 /* high performance */
94 #define POLICY_POWERSAVE 2 /* high power saving */
95 #define POLICY_POWER_SUPERSAVE 3 /* possibly even more power saving */
97 #ifdef CONFIG_PCIEASPM_PERFORMANCE
98 static int aspm_policy = POLICY_PERFORMANCE;
99 #elif defined CONFIG_PCIEASPM_POWERSAVE
100 static int aspm_policy = POLICY_POWERSAVE;
101 #elif defined CONFIG_PCIEASPM_POWER_SUPERSAVE
102 static int aspm_policy = POLICY_POWER_SUPERSAVE;
104 static int aspm_policy;
107 static const char *policy_str[] = {
108 [POLICY_DEFAULT] = "default",
109 [POLICY_PERFORMANCE] = "performance",
110 [POLICY_POWERSAVE] = "powersave",
111 [POLICY_POWER_SUPERSAVE] = "powersupersave"
114 #define LINK_RETRAIN_TIMEOUT HZ
116 static int policy_to_aspm_state(struct pcie_link_state *link)
118 switch (aspm_policy) {
119 case POLICY_PERFORMANCE:
120 /* Disable ASPM and Clock PM */
122 case POLICY_POWERSAVE:
123 /* Enable ASPM L0s/L1 */
124 return (ASPM_STATE_L0S | ASPM_STATE_L1);
125 case POLICY_POWER_SUPERSAVE:
126 /* Enable Everything */
127 return ASPM_STATE_ALL;
129 return link->aspm_default;
134 static int policy_to_clkpm_state(struct pcie_link_state *link)
136 switch (aspm_policy) {
137 case POLICY_PERFORMANCE:
138 /* Disable ASPM and Clock PM */
140 case POLICY_POWERSAVE:
141 case POLICY_POWER_SUPERSAVE:
142 /* Enable Clock PM */
145 return link->clkpm_default;
150 static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
152 struct pci_dev *child;
153 struct pci_bus *linkbus = link->pdev->subordinate;
154 u32 val = enable ? PCI_EXP_LNKCTL_CLKREQ_EN : 0;
156 list_for_each_entry(child, &linkbus->devices, bus_list)
157 pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
158 PCI_EXP_LNKCTL_CLKREQ_EN,
160 link->clkpm_enabled = !!enable;
163 static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
166 * Don't enable Clock PM if the link is not Clock PM capable
167 * or Clock PM is disabled
169 if (!link->clkpm_capable || link->clkpm_disable)
171 /* Need nothing if the specified equals to current state */
172 if (link->clkpm_enabled == enable)
174 pcie_set_clkpm_nocheck(link, enable);
177 static void pcie_clkpm_cap_init(struct pcie_link_state *link, int blacklist)
179 int capable = 1, enabled = 1;
182 struct pci_dev *child;
183 struct pci_bus *linkbus = link->pdev->subordinate;
185 /* All functions should have the same cap and state, take the worst */
186 list_for_each_entry(child, &linkbus->devices, bus_list) {
187 pcie_capability_read_dword(child, PCI_EXP_LNKCAP, ®32);
188 if (!(reg32 & PCI_EXP_LNKCAP_CLKPM)) {
193 pcie_capability_read_word(child, PCI_EXP_LNKCTL, ®16);
194 if (!(reg16 & PCI_EXP_LNKCTL_CLKREQ_EN))
197 link->clkpm_enabled = enabled;
198 link->clkpm_default = enabled;
199 link->clkpm_capable = capable;
200 link->clkpm_disable = blacklist ? 1 : 0;
203 static bool pcie_retrain_link(struct pcie_link_state *link)
205 struct pci_dev *parent = link->pdev;
206 unsigned long end_jiffies;
209 pcie_capability_read_word(parent, PCI_EXP_LNKCTL, ®16);
210 reg16 |= PCI_EXP_LNKCTL_RL;
211 pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
212 if (parent->clear_retrain_link) {
214 * Due to an erratum in some devices the Retrain Link bit
215 * needs to be cleared again manually to allow the link
216 * training to succeed.
218 reg16 &= ~PCI_EXP_LNKCTL_RL;
219 pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
222 /* Wait for link training end. Break out after waiting for timeout */
223 end_jiffies = jiffies + LINK_RETRAIN_TIMEOUT;
225 pcie_capability_read_word(parent, PCI_EXP_LNKSTA, ®16);
226 if (!(reg16 & PCI_EXP_LNKSTA_LT))
229 } while (time_before(jiffies, end_jiffies));
230 return !(reg16 & PCI_EXP_LNKSTA_LT);
234 * pcie_aspm_configure_common_clock: check if the 2 ends of a link
235 * could use common clock. If they are, configure them to use the
236 * common clock. That will reduce the ASPM state exit latency.
238 static void pcie_aspm_configure_common_clock(struct pcie_link_state *link)
241 u16 reg16, parent_reg, child_reg[8];
242 struct pci_dev *child, *parent = link->pdev;
243 struct pci_bus *linkbus = parent->subordinate;
245 * All functions of a slot should have the same Slot Clock
246 * Configuration, so just check one function
248 child = list_entry(linkbus->devices.next, struct pci_dev, bus_list);
249 BUG_ON(!pci_is_pcie(child));
251 /* Check downstream component if bit Slot Clock Configuration is 1 */
252 pcie_capability_read_word(child, PCI_EXP_LNKSTA, ®16);
253 if (!(reg16 & PCI_EXP_LNKSTA_SLC))
256 /* Check upstream component if bit Slot Clock Configuration is 1 */
257 pcie_capability_read_word(parent, PCI_EXP_LNKSTA, ®16);
258 if (!(reg16 & PCI_EXP_LNKSTA_SLC))
261 /* Port might be already in common clock mode */
262 pcie_capability_read_word(parent, PCI_EXP_LNKCTL, ®16);
263 if (same_clock && (reg16 & PCI_EXP_LNKCTL_CCC)) {
264 bool consistent = true;
266 list_for_each_entry(child, &linkbus->devices, bus_list) {
267 pcie_capability_read_word(child, PCI_EXP_LNKCTL,
269 if (!(reg16 & PCI_EXP_LNKCTL_CCC)) {
276 pci_info(parent, "ASPM: current common clock configuration is inconsistent, reconfiguring\n");
279 /* Configure downstream component, all functions */
280 list_for_each_entry(child, &linkbus->devices, bus_list) {
281 pcie_capability_read_word(child, PCI_EXP_LNKCTL, ®16);
282 child_reg[PCI_FUNC(child->devfn)] = reg16;
284 reg16 |= PCI_EXP_LNKCTL_CCC;
286 reg16 &= ~PCI_EXP_LNKCTL_CCC;
287 pcie_capability_write_word(child, PCI_EXP_LNKCTL, reg16);
290 /* Configure upstream component */
291 pcie_capability_read_word(parent, PCI_EXP_LNKCTL, ®16);
294 reg16 |= PCI_EXP_LNKCTL_CCC;
296 reg16 &= ~PCI_EXP_LNKCTL_CCC;
297 pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
299 if (pcie_retrain_link(link))
302 /* Training failed. Restore common clock configurations */
303 pci_err(parent, "ASPM: Could not configure common clock\n");
304 list_for_each_entry(child, &linkbus->devices, bus_list)
305 pcie_capability_write_word(child, PCI_EXP_LNKCTL,
306 child_reg[PCI_FUNC(child->devfn)]);
307 pcie_capability_write_word(parent, PCI_EXP_LNKCTL, parent_reg);
310 /* Convert L0s latency encoding to ns */
311 static u32 calc_l0s_latency(u32 lnkcap)
313 u32 encoding = (lnkcap & PCI_EXP_LNKCAP_L0SEL) >> 12;
316 return (5 * 1000); /* > 4us */
317 return (64 << encoding);
320 /* Convert L0s acceptable latency encoding to ns */
321 static u32 calc_l0s_acceptable(u32 encoding)
325 return (64 << encoding);
328 /* Convert L1 latency encoding to ns */
329 static u32 calc_l1_latency(u32 lnkcap)
331 u32 encoding = (lnkcap & PCI_EXP_LNKCAP_L1EL) >> 15;
334 return (65 * 1000); /* > 64us */
335 return (1000 << encoding);
338 /* Convert L1 acceptable latency encoding to ns */
339 static u32 calc_l1_acceptable(u32 encoding)
343 return (1000 << encoding);
346 /* Convert L1SS T_pwr encoding to usec */
347 static u32 calc_l1ss_pwron(struct pci_dev *pdev, u32 scale, u32 val)
357 pci_err(pdev, "%s: Invalid T_PwrOn scale: %u\n", __func__, scale);
361 static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
363 u32 threshold_ns = threshold_us * 1000;
365 /* See PCIe r3.1, sec 7.33.3 and sec 6.18 */
366 if (threshold_ns < 32) {
368 *value = threshold_ns;
369 } else if (threshold_ns < 1024) {
371 *value = threshold_ns >> 5;
372 } else if (threshold_ns < 32768) {
374 *value = threshold_ns >> 10;
375 } else if (threshold_ns < 1048576) {
377 *value = threshold_ns >> 15;
378 } else if (threshold_ns < 33554432) {
380 *value = threshold_ns >> 20;
383 *value = threshold_ns >> 25;
387 struct aspm_register_info {
395 static void pcie_get_aspm_reg(struct pci_dev *pdev,
396 struct aspm_register_info *info)
398 /* Read L1 PM substate capabilities */
399 info->l1ss_cap = info->l1ss_ctl1 = info->l1ss_ctl2 = 0;
400 info->l1ss_cap_ptr = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_L1SS);
401 if (!info->l1ss_cap_ptr)
403 pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CAP,
405 if (!(info->l1ss_cap & PCI_L1SS_CAP_L1_PM_SS)) {
410 pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL1,
412 pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL2,
416 static void pcie_aspm_check_latency(struct pci_dev *endpoint)
418 u32 latency, l1_switch_latency = 0;
419 struct aspm_latency *acceptable;
420 struct pcie_link_state *link;
422 /* Device not in D0 doesn't need latency check */
423 if ((endpoint->current_state != PCI_D0) &&
424 (endpoint->current_state != PCI_UNKNOWN))
427 link = endpoint->bus->self->link_state;
428 acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];
431 /* Check upstream direction L0s latency */
432 if ((link->aspm_capable & ASPM_STATE_L0S_UP) &&
433 (link->latency_up.l0s > acceptable->l0s))
434 link->aspm_capable &= ~ASPM_STATE_L0S_UP;
436 /* Check downstream direction L0s latency */
437 if ((link->aspm_capable & ASPM_STATE_L0S_DW) &&
438 (link->latency_dw.l0s > acceptable->l0s))
439 link->aspm_capable &= ~ASPM_STATE_L0S_DW;
442 * Every switch on the path to root complex need 1
443 * more microsecond for L1. Spec doesn't mention L0s.
445 * The exit latencies for L1 substates are not advertised
446 * by a device. Since the spec also doesn't mention a way
447 * to determine max latencies introduced by enabling L1
448 * substates on the components, it is not clear how to do
449 * a L1 substate exit latency check. We assume that the
450 * L1 exit latencies advertised by a device include L1
451 * substate latencies (and hence do not do any check).
453 latency = max_t(u32, link->latency_up.l1, link->latency_dw.l1);
454 if ((link->aspm_capable & ASPM_STATE_L1) &&
455 (latency + l1_switch_latency > acceptable->l1))
456 link->aspm_capable &= ~ASPM_STATE_L1;
457 l1_switch_latency += 1000;
464 * The L1 PM substate capability is only implemented in function 0 in a
465 * multi function device.
467 static struct pci_dev *pci_function_0(struct pci_bus *linkbus)
469 struct pci_dev *child;
471 list_for_each_entry(child, &linkbus->devices, bus_list)
472 if (PCI_FUNC(child->devfn) == 0)
477 static void pci_clear_and_set_dword(struct pci_dev *pdev, int pos,
482 pci_read_config_dword(pdev, pos, &val);
485 pci_write_config_dword(pdev, pos, val);
488 /* Calculate L1.2 PM substate timing parameters */
489 static void aspm_calc_l1ss_info(struct pcie_link_state *link,
490 struct aspm_register_info *upreg,
491 struct aspm_register_info *dwreg)
493 struct pci_dev *child = link->downstream, *parent = link->pdev;
494 u32 val1, val2, scale1, scale2;
495 u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
497 link->l1ss.up_cap_ptr = upreg->l1ss_cap_ptr;
498 link->l1ss.dw_cap_ptr = dwreg->l1ss_cap_ptr;
499 link->l1ss.ctl1 = link->l1ss.ctl2 = 0;
501 if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
504 /* Choose the greater of the two Port Common_Mode_Restore_Times */
505 val1 = (upreg->l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
506 val2 = (dwreg->l1ss_cap & PCI_L1SS_CAP_CM_RESTORE_TIME) >> 8;
507 t_common_mode = max(val1, val2);
509 /* Choose the greater of the two Port T_POWER_ON times */
510 val1 = (upreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_VALUE) >> 19;
511 scale1 = (upreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_SCALE) >> 16;
512 val2 = (dwreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_VALUE) >> 19;
513 scale2 = (dwreg->l1ss_cap & PCI_L1SS_CAP_P_PWR_ON_SCALE) >> 16;
515 if (calc_l1ss_pwron(parent, scale1, val1) >
516 calc_l1ss_pwron(child, scale2, val2)) {
517 link->l1ss.ctl2 |= scale1 | (val1 << 3);
518 t_power_on = calc_l1ss_pwron(parent, scale1, val1);
520 link->l1ss.ctl2 |= scale2 | (val2 << 3);
521 t_power_on = calc_l1ss_pwron(child, scale2, val2);
525 * Set LTR_L1.2_THRESHOLD to the time required to transition the
526 * Link from L0 to L1.2 and back to L0 so we enter L1.2 only if
527 * downstream devices report (via LTR) that they can tolerate at
528 * least that much latency.
530 * Based on PCIe r3.1, sec 5.5.3.3.1, Figures 5-16 and 5-17, and
531 * Table 5-11. T(POWER_OFF) is at most 2us and T(L1.2) is at
534 l1_2_threshold = 2 + 4 + t_common_mode + t_power_on;
535 encode_l12_threshold(l1_2_threshold, &scale, &value);
536 link->l1ss.ctl1 |= t_common_mode << 8 | scale << 29 | value << 16;
539 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
541 struct pci_dev *child = link->downstream, *parent = link->pdev;
542 u32 parent_lnkcap, child_lnkcap;
543 u16 parent_lnkctl, child_lnkctl;
544 struct pci_bus *linkbus = parent->subordinate;
545 struct aspm_register_info upreg, dwreg;
548 /* Set enabled/disable so that we will disable ASPM later */
549 link->aspm_enabled = ASPM_STATE_ALL;
550 link->aspm_disable = ASPM_STATE_ALL;
555 * If ASPM not supported, don't mess with the clocks and link,
558 pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &parent_lnkcap);
559 pcie_capability_read_dword(child, PCI_EXP_LNKCAP, &child_lnkcap);
560 if (!(parent_lnkcap & child_lnkcap & PCI_EXP_LNKCAP_ASPMS))
563 /* Configure common clock before checking latencies */
564 pcie_aspm_configure_common_clock(link);
567 * Re-read upstream/downstream components' register state after
568 * clock configuration. L0s & L1 exit latencies in the otherwise
569 * read-only Link Capabilities may change depending on common clock
570 * configuration (PCIe r5.0, sec 7.5.3.6).
572 pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &parent_lnkcap);
573 pcie_capability_read_dword(child, PCI_EXP_LNKCAP, &child_lnkcap);
574 pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &parent_lnkctl);
575 pcie_capability_read_word(child, PCI_EXP_LNKCTL, &child_lnkctl);
576 pcie_get_aspm_reg(parent, &upreg);
577 pcie_get_aspm_reg(child, &dwreg);
582 * Note that we must not enable L0s in either direction on a
583 * given link unless components on both sides of the link each
586 if (parent_lnkcap & child_lnkcap & PCI_EXP_LNKCAP_ASPM_L0S)
587 link->aspm_support |= ASPM_STATE_L0S;
589 if (child_lnkctl & PCI_EXP_LNKCTL_ASPM_L0S)
590 link->aspm_enabled |= ASPM_STATE_L0S_UP;
591 if (parent_lnkctl & PCI_EXP_LNKCTL_ASPM_L0S)
592 link->aspm_enabled |= ASPM_STATE_L0S_DW;
593 link->latency_up.l0s = calc_l0s_latency(parent_lnkcap);
594 link->latency_dw.l0s = calc_l0s_latency(child_lnkcap);
597 if (parent_lnkcap & child_lnkcap & PCI_EXP_LNKCAP_ASPM_L1)
598 link->aspm_support |= ASPM_STATE_L1;
600 if (parent_lnkctl & child_lnkctl & PCI_EXP_LNKCTL_ASPM_L1)
601 link->aspm_enabled |= ASPM_STATE_L1;
602 link->latency_up.l1 = calc_l1_latency(parent_lnkcap);
603 link->latency_dw.l1 = calc_l1_latency(child_lnkcap);
606 * If we don't have LTR for the entire path from the Root Complex
607 * to this device, we can't use ASPM L1.2 because it relies on the
608 * LTR_L1.2_THRESHOLD. See PCIe r4.0, secs 5.5.4, 6.18.
610 if (!child->ltr_path)
611 dwreg.l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2;
613 if (upreg.l1ss_cap & dwreg.l1ss_cap & PCI_L1SS_CAP_ASPM_L1_1)
614 link->aspm_support |= ASPM_STATE_L1_1;
615 if (upreg.l1ss_cap & dwreg.l1ss_cap & PCI_L1SS_CAP_ASPM_L1_2)
616 link->aspm_support |= ASPM_STATE_L1_2;
617 if (upreg.l1ss_cap & dwreg.l1ss_cap & PCI_L1SS_CAP_PCIPM_L1_1)
618 link->aspm_support |= ASPM_STATE_L1_1_PCIPM;
619 if (upreg.l1ss_cap & dwreg.l1ss_cap & PCI_L1SS_CAP_PCIPM_L1_2)
620 link->aspm_support |= ASPM_STATE_L1_2_PCIPM;
622 if (upreg.l1ss_ctl1 & dwreg.l1ss_ctl1 & PCI_L1SS_CTL1_ASPM_L1_1)
623 link->aspm_enabled |= ASPM_STATE_L1_1;
624 if (upreg.l1ss_ctl1 & dwreg.l1ss_ctl1 & PCI_L1SS_CTL1_ASPM_L1_2)
625 link->aspm_enabled |= ASPM_STATE_L1_2;
626 if (upreg.l1ss_ctl1 & dwreg.l1ss_ctl1 & PCI_L1SS_CTL1_PCIPM_L1_1)
627 link->aspm_enabled |= ASPM_STATE_L1_1_PCIPM;
628 if (upreg.l1ss_ctl1 & dwreg.l1ss_ctl1 & PCI_L1SS_CTL1_PCIPM_L1_2)
629 link->aspm_enabled |= ASPM_STATE_L1_2_PCIPM;
631 if (link->aspm_support & ASPM_STATE_L1SS)
632 aspm_calc_l1ss_info(link, &upreg, &dwreg);
634 /* Save default state */
635 link->aspm_default = link->aspm_enabled;
637 /* Setup initial capable state. Will be updated later */
638 link->aspm_capable = link->aspm_support;
640 /* Get and check endpoint acceptable latencies */
641 list_for_each_entry(child, &linkbus->devices, bus_list) {
643 struct aspm_latency *acceptable =
644 &link->acceptable[PCI_FUNC(child->devfn)];
646 if (pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT &&
647 pci_pcie_type(child) != PCI_EXP_TYPE_LEG_END)
650 pcie_capability_read_dword(child, PCI_EXP_DEVCAP, ®32);
651 /* Calculate endpoint L0s acceptable latency */
652 encoding = (reg32 & PCI_EXP_DEVCAP_L0S) >> 6;
653 acceptable->l0s = calc_l0s_acceptable(encoding);
654 /* Calculate endpoint L1 acceptable latency */
655 encoding = (reg32 & PCI_EXP_DEVCAP_L1) >> 9;
656 acceptable->l1 = calc_l1_acceptable(encoding);
658 pcie_aspm_check_latency(child);
662 /* Configure the ASPM L1 substates */
663 static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
666 struct pci_dev *child = link->downstream, *parent = link->pdev;
667 u32 up_cap_ptr = link->l1ss.up_cap_ptr;
668 u32 dw_cap_ptr = link->l1ss.dw_cap_ptr;
670 enable_req = (link->aspm_enabled ^ state) & state;
673 * Here are the rules specified in the PCIe spec for enabling L1SS:
674 * - When enabling L1.x, enable bit at parent first, then at child
675 * - When disabling L1.x, disable bit at child first, then at parent
676 * - When enabling ASPM L1.x, need to disable L1
677 * (at child followed by parent).
678 * - The ASPM/PCIPM L1.2 must be disabled while programming timing
681 * To keep it simple, disable all L1SS bits first, and later enable
685 /* Disable all L1 substates */
686 pci_clear_and_set_dword(child, dw_cap_ptr + PCI_L1SS_CTL1,
687 PCI_L1SS_CTL1_L1SS_MASK, 0);
688 pci_clear_and_set_dword(parent, up_cap_ptr + PCI_L1SS_CTL1,
689 PCI_L1SS_CTL1_L1SS_MASK, 0);
691 * If needed, disable L1, and it gets enabled later
692 * in pcie_config_aspm_link().
694 if (enable_req & (ASPM_STATE_L1_1 | ASPM_STATE_L1_2)) {
695 pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
696 PCI_EXP_LNKCTL_ASPM_L1, 0);
697 pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL,
698 PCI_EXP_LNKCTL_ASPM_L1, 0);
701 if (enable_req & ASPM_STATE_L1_2_MASK) {
703 /* Program T_POWER_ON times in both ports */
704 pci_write_config_dword(parent, up_cap_ptr + PCI_L1SS_CTL2,
706 pci_write_config_dword(child, dw_cap_ptr + PCI_L1SS_CTL2,
709 /* Program Common_Mode_Restore_Time in upstream device */
710 pci_clear_and_set_dword(parent, up_cap_ptr + PCI_L1SS_CTL1,
711 PCI_L1SS_CTL1_CM_RESTORE_TIME,
714 /* Program LTR_L1.2_THRESHOLD time in both ports */
715 pci_clear_and_set_dword(parent, up_cap_ptr + PCI_L1SS_CTL1,
716 PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
717 PCI_L1SS_CTL1_LTR_L12_TH_SCALE,
719 pci_clear_and_set_dword(child, dw_cap_ptr + PCI_L1SS_CTL1,
720 PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
721 PCI_L1SS_CTL1_LTR_L12_TH_SCALE,
726 if (state & ASPM_STATE_L1_1)
727 val |= PCI_L1SS_CTL1_ASPM_L1_1;
728 if (state & ASPM_STATE_L1_2)
729 val |= PCI_L1SS_CTL1_ASPM_L1_2;
730 if (state & ASPM_STATE_L1_1_PCIPM)
731 val |= PCI_L1SS_CTL1_PCIPM_L1_1;
732 if (state & ASPM_STATE_L1_2_PCIPM)
733 val |= PCI_L1SS_CTL1_PCIPM_L1_2;
735 /* Enable what we need to enable */
736 pci_clear_and_set_dword(parent, up_cap_ptr + PCI_L1SS_CTL1,
737 PCI_L1SS_CTL1_L1SS_MASK, val);
738 pci_clear_and_set_dword(child, dw_cap_ptr + PCI_L1SS_CTL1,
739 PCI_L1SS_CTL1_L1SS_MASK, val);
742 static void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
744 pcie_capability_clear_and_set_word(pdev, PCI_EXP_LNKCTL,
745 PCI_EXP_LNKCTL_ASPMC, val);
748 static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
750 u32 upstream = 0, dwstream = 0;
751 struct pci_dev *child = link->downstream, *parent = link->pdev;
752 struct pci_bus *linkbus = parent->subordinate;
754 /* Enable only the states that were not explicitly disabled */
755 state &= (link->aspm_capable & ~link->aspm_disable);
757 /* Can't enable any substates if L1 is not enabled */
758 if (!(state & ASPM_STATE_L1))
759 state &= ~ASPM_STATE_L1SS;
761 /* Spec says both ports must be in D0 before enabling PCI PM substates*/
762 if (parent->current_state != PCI_D0 || child->current_state != PCI_D0) {
763 state &= ~ASPM_STATE_L1_SS_PCIPM;
764 state |= (link->aspm_enabled & ASPM_STATE_L1_SS_PCIPM);
767 /* Nothing to do if the link is already in the requested state */
768 if (link->aspm_enabled == state)
770 /* Convert ASPM state to upstream/downstream ASPM register state */
771 if (state & ASPM_STATE_L0S_UP)
772 dwstream |= PCI_EXP_LNKCTL_ASPM_L0S;
773 if (state & ASPM_STATE_L0S_DW)
774 upstream |= PCI_EXP_LNKCTL_ASPM_L0S;
775 if (state & ASPM_STATE_L1) {
776 upstream |= PCI_EXP_LNKCTL_ASPM_L1;
777 dwstream |= PCI_EXP_LNKCTL_ASPM_L1;
780 if (link->aspm_capable & ASPM_STATE_L1SS)
781 pcie_config_aspm_l1ss(link, state);
784 * Spec 2.0 suggests all functions should be configured the
785 * same setting for ASPM. Enabling ASPM L1 should be done in
786 * upstream component first and then downstream, and vice
787 * versa for disabling ASPM L1. Spec doesn't mention L0S.
789 if (state & ASPM_STATE_L1)
790 pcie_config_aspm_dev(parent, upstream);
791 list_for_each_entry(child, &linkbus->devices, bus_list)
792 pcie_config_aspm_dev(child, dwstream);
793 if (!(state & ASPM_STATE_L1))
794 pcie_config_aspm_dev(parent, upstream);
796 link->aspm_enabled = state;
799 static void pcie_config_aspm_path(struct pcie_link_state *link)
802 pcie_config_aspm_link(link, policy_to_aspm_state(link));
807 static void free_link_state(struct pcie_link_state *link)
809 link->pdev->link_state = NULL;
813 static int pcie_aspm_sanity_check(struct pci_dev *pdev)
815 struct pci_dev *child;
819 * Some functions in a slot might not all be PCIe functions,
820 * very strange. Disable ASPM for the whole slot
822 list_for_each_entry(child, &pdev->subordinate->devices, bus_list) {
823 if (!pci_is_pcie(child))
827 * If ASPM is disabled then we're not going to change
828 * the BIOS state. It's safe to continue even if it's a
836 * Disable ASPM for pre-1.1 PCIe device, we follow MS to use
837 * RBER bit to determine if a function is 1.1 version device
839 pcie_capability_read_dword(child, PCI_EXP_DEVCAP, ®32);
840 if (!(reg32 & PCI_EXP_DEVCAP_RBER) && !aspm_force) {
841 pci_info(child, "disabling ASPM on pre-1.1 PCIe device. You can enable it with 'pcie_aspm=force'\n");
848 static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
850 struct pcie_link_state *link;
852 link = kzalloc(sizeof(*link), GFP_KERNEL);
856 INIT_LIST_HEAD(&link->sibling);
858 link->downstream = pci_function_0(pdev->subordinate);
861 * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe
862 * hierarchies. Note that some PCIe host implementations omit
863 * the root ports entirely, in which case a downstream port on
864 * a switch may become the root of the link state chain for all
865 * its subordinate endpoints.
867 if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT ||
868 pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE ||
869 !pdev->bus->parent->self) {
872 struct pcie_link_state *parent;
874 parent = pdev->bus->parent->self->link_state;
880 link->parent = parent;
881 link->root = link->parent->root;
884 list_add(&link->sibling, &link_list);
885 pdev->link_state = link;
889 static void pcie_aspm_update_sysfs_visibility(struct pci_dev *pdev)
891 struct pci_dev *child;
893 list_for_each_entry(child, &pdev->subordinate->devices, bus_list)
894 sysfs_update_group(&child->dev.kobj, &aspm_ctrl_attr_group);
898 * pcie_aspm_init_link_state: Initiate PCI express link state.
899 * It is called after the pcie and its children devices are scanned.
900 * @pdev: the root port or switch downstream port
902 void pcie_aspm_init_link_state(struct pci_dev *pdev)
904 struct pcie_link_state *link;
905 int blacklist = !!pcie_aspm_sanity_check(pdev);
907 if (!aspm_support_enabled)
910 if (pdev->link_state)
914 * We allocate pcie_link_state for the component on the upstream
915 * end of a Link, so there's nothing to do unless this device is
918 if (!pcie_downstream_port(pdev))
921 /* VIA has a strange chipset, root port is under a bridge */
922 if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT &&
926 down_read(&pci_bus_sem);
927 if (list_empty(&pdev->subordinate->devices))
930 mutex_lock(&aspm_lock);
931 link = alloc_pcie_link_state(pdev);
935 * Setup initial ASPM state. Note that we need to configure
936 * upstream links also because capable state of them can be
937 * update through pcie_aspm_cap_init().
939 pcie_aspm_cap_init(link, blacklist);
941 /* Setup initial Clock PM state */
942 pcie_clkpm_cap_init(link, blacklist);
945 * At this stage drivers haven't had an opportunity to change the
946 * link policy setting. Enabling ASPM on broken hardware can cripple
947 * it even before the driver has had a chance to disable ASPM, so
948 * default to a safe level right now. If we're enabling ASPM beyond
949 * the BIOS's expectation, we'll do so once pci_enable_device() is
952 if (aspm_policy != POLICY_POWERSAVE &&
953 aspm_policy != POLICY_POWER_SUPERSAVE) {
954 pcie_config_aspm_path(link);
955 pcie_set_clkpm(link, policy_to_clkpm_state(link));
958 pcie_aspm_update_sysfs_visibility(pdev);
961 mutex_unlock(&aspm_lock);
963 up_read(&pci_bus_sem);
966 /* Recheck latencies and update aspm_capable for links under the root */
967 static void pcie_update_aspm_capable(struct pcie_link_state *root)
969 struct pcie_link_state *link;
970 BUG_ON(root->parent);
971 list_for_each_entry(link, &link_list, sibling) {
972 if (link->root != root)
974 link->aspm_capable = link->aspm_support;
976 list_for_each_entry(link, &link_list, sibling) {
977 struct pci_dev *child;
978 struct pci_bus *linkbus = link->pdev->subordinate;
979 if (link->root != root)
981 list_for_each_entry(child, &linkbus->devices, bus_list) {
982 if ((pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT) &&
983 (pci_pcie_type(child) != PCI_EXP_TYPE_LEG_END))
985 pcie_aspm_check_latency(child);
990 /* @pdev: the endpoint device */
991 void pcie_aspm_exit_link_state(struct pci_dev *pdev)
993 struct pci_dev *parent = pdev->bus->self;
994 struct pcie_link_state *link, *root, *parent_link;
996 if (!parent || !parent->link_state)
999 down_read(&pci_bus_sem);
1000 mutex_lock(&aspm_lock);
1002 * All PCIe functions are in one slot, remove one function will remove
1003 * the whole slot, so just wait until we are the last function left.
1005 if (!list_empty(&parent->subordinate->devices))
1008 link = parent->link_state;
1010 parent_link = link->parent;
1012 /* All functions are removed, so just disable ASPM for the link */
1013 pcie_config_aspm_link(link, 0);
1014 list_del(&link->sibling);
1015 /* Clock PM is for endpoint device */
1016 free_link_state(link);
1018 /* Recheck latencies and configure upstream links */
1020 pcie_update_aspm_capable(root);
1021 pcie_config_aspm_path(parent_link);
1024 mutex_unlock(&aspm_lock);
1025 up_read(&pci_bus_sem);
1028 /* @pdev: the root port or switch downstream port */
1029 void pcie_aspm_pm_state_change(struct pci_dev *pdev)
1031 struct pcie_link_state *link = pdev->link_state;
1033 if (aspm_disabled || !link)
1036 * Devices changed PM state, we should recheck if latency
1037 * meets all functions' requirement
1039 down_read(&pci_bus_sem);
1040 mutex_lock(&aspm_lock);
1041 pcie_update_aspm_capable(link->root);
1042 pcie_config_aspm_path(link);
1043 mutex_unlock(&aspm_lock);
1044 up_read(&pci_bus_sem);
1047 void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
1049 struct pcie_link_state *link = pdev->link_state;
1051 if (aspm_disabled || !link)
1054 if (aspm_policy != POLICY_POWERSAVE &&
1055 aspm_policy != POLICY_POWER_SUPERSAVE)
1058 down_read(&pci_bus_sem);
1059 mutex_lock(&aspm_lock);
1060 pcie_config_aspm_path(link);
1061 pcie_set_clkpm(link, policy_to_clkpm_state(link));
1062 mutex_unlock(&aspm_lock);
1063 up_read(&pci_bus_sem);
1066 static struct pcie_link_state *pcie_aspm_get_link(struct pci_dev *pdev)
1068 struct pci_dev *bridge;
1070 if (!pci_is_pcie(pdev))
1073 bridge = pci_upstream_bridge(pdev);
1074 if (!bridge || !pci_is_pcie(bridge))
1077 return bridge->link_state;
1080 static int __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
1082 struct pcie_link_state *link = pcie_aspm_get_link(pdev);
1087 * A driver requested that ASPM be disabled on this device, but
1088 * if we don't have permission to manage ASPM (e.g., on ACPI
1089 * systems we have to observe the FADT ACPI_FADT_NO_ASPM bit and
1090 * the _OSC method), we can't honor that request. Windows has
1091 * a similar mechanism using "PciASPMOptOut", which is also
1092 * ignored in this situation.
1094 if (aspm_disabled) {
1095 pci_warn(pdev, "can't disable ASPM; OS doesn't have ASPM control\n");
1100 down_read(&pci_bus_sem);
1101 mutex_lock(&aspm_lock);
1102 if (state & PCIE_LINK_STATE_L0S)
1103 link->aspm_disable |= ASPM_STATE_L0S;
1104 if (state & PCIE_LINK_STATE_L1)
1105 /* L1 PM substates require L1 */
1106 link->aspm_disable |= ASPM_STATE_L1 | ASPM_STATE_L1SS;
1107 if (state & PCIE_LINK_STATE_L1_1)
1108 link->aspm_disable |= ASPM_STATE_L1_1;
1109 if (state & PCIE_LINK_STATE_L1_2)
1110 link->aspm_disable |= ASPM_STATE_L1_2;
1111 if (state & PCIE_LINK_STATE_L1_1_PCIPM)
1112 link->aspm_disable |= ASPM_STATE_L1_1_PCIPM;
1113 if (state & PCIE_LINK_STATE_L1_2_PCIPM)
1114 link->aspm_disable |= ASPM_STATE_L1_2_PCIPM;
1115 pcie_config_aspm_link(link, policy_to_aspm_state(link));
1117 if (state & PCIE_LINK_STATE_CLKPM)
1118 link->clkpm_disable = 1;
1119 pcie_set_clkpm(link, policy_to_clkpm_state(link));
1120 mutex_unlock(&aspm_lock);
1122 up_read(&pci_bus_sem);
1127 int pci_disable_link_state_locked(struct pci_dev *pdev, int state)
1129 return __pci_disable_link_state(pdev, state, false);
1131 EXPORT_SYMBOL(pci_disable_link_state_locked);
1134 * pci_disable_link_state - Disable device's link state, so the link will
1135 * never enter specific states. Note that if the BIOS didn't grant ASPM
1136 * control to the OS, this does nothing because we can't touch the LNKCTL
1137 * register. Returns 0 or a negative errno.
1140 * @state: ASPM link state to disable
1142 int pci_disable_link_state(struct pci_dev *pdev, int state)
1144 return __pci_disable_link_state(pdev, state, true);
1146 EXPORT_SYMBOL(pci_disable_link_state);
1148 static int pcie_aspm_set_policy(const char *val,
1149 const struct kernel_param *kp)
1152 struct pcie_link_state *link;
1156 i = sysfs_match_string(policy_str, val);
1159 if (i == aspm_policy)
1162 down_read(&pci_bus_sem);
1163 mutex_lock(&aspm_lock);
1165 list_for_each_entry(link, &link_list, sibling) {
1166 pcie_config_aspm_link(link, policy_to_aspm_state(link));
1167 pcie_set_clkpm(link, policy_to_clkpm_state(link));
1169 mutex_unlock(&aspm_lock);
1170 up_read(&pci_bus_sem);
1174 static int pcie_aspm_get_policy(char *buffer, const struct kernel_param *kp)
1177 for (i = 0; i < ARRAY_SIZE(policy_str); i++)
1178 if (i == aspm_policy)
1179 cnt += sprintf(buffer + cnt, "[%s] ", policy_str[i]);
1181 cnt += sprintf(buffer + cnt, "%s ", policy_str[i]);
1182 cnt += sprintf(buffer + cnt, "\n");
1186 module_param_call(policy, pcie_aspm_set_policy, pcie_aspm_get_policy,
1190 * pcie_aspm_enabled - Check if PCIe ASPM has been enabled for a device.
1191 * @pdev: Target device.
1193 * Relies on the upstream bridge's link_state being valid. The link_state
1194 * is deallocated only when the last child of the bridge (i.e., @pdev or a
1195 * sibling) is removed, and the caller should be holding a reference to
1196 * @pdev, so this should be safe.
1198 bool pcie_aspm_enabled(struct pci_dev *pdev)
1200 struct pcie_link_state *link = pcie_aspm_get_link(pdev);
1205 return link->aspm_enabled;
1207 EXPORT_SYMBOL_GPL(pcie_aspm_enabled);
1209 static ssize_t aspm_attr_show_common(struct device *dev,
1210 struct device_attribute *attr,
1211 char *buf, u8 state)
1213 struct pci_dev *pdev = to_pci_dev(dev);
1214 struct pcie_link_state *link = pcie_aspm_get_link(pdev);
1216 return sprintf(buf, "%d\n", (link->aspm_enabled & state) ? 1 : 0);
1219 static ssize_t aspm_attr_store_common(struct device *dev,
1220 struct device_attribute *attr,
1221 const char *buf, size_t len, u8 state)
1223 struct pci_dev *pdev = to_pci_dev(dev);
1224 struct pcie_link_state *link = pcie_aspm_get_link(pdev);
1227 if (strtobool(buf, &state_enable) < 0)
1230 down_read(&pci_bus_sem);
1231 mutex_lock(&aspm_lock);
1234 link->aspm_disable &= ~state;
1235 /* need to enable L1 for substates */
1236 if (state & ASPM_STATE_L1SS)
1237 link->aspm_disable &= ~ASPM_STATE_L1;
1239 link->aspm_disable |= state;
1242 pcie_config_aspm_link(link, policy_to_aspm_state(link));
1244 mutex_unlock(&aspm_lock);
1245 up_read(&pci_bus_sem);
1250 #define ASPM_ATTR(_f, _s) \
1251 static ssize_t _f##_show(struct device *dev, \
1252 struct device_attribute *attr, char *buf) \
1253 { return aspm_attr_show_common(dev, attr, buf, ASPM_STATE_##_s); } \
1255 static ssize_t _f##_store(struct device *dev, \
1256 struct device_attribute *attr, \
1257 const char *buf, size_t len) \
1258 { return aspm_attr_store_common(dev, attr, buf, len, ASPM_STATE_##_s); }
1260 ASPM_ATTR(l0s_aspm, L0S)
1261 ASPM_ATTR(l1_aspm, L1)
1262 ASPM_ATTR(l1_1_aspm, L1_1)
1263 ASPM_ATTR(l1_2_aspm, L1_2)
1264 ASPM_ATTR(l1_1_pcipm, L1_1_PCIPM)
1265 ASPM_ATTR(l1_2_pcipm, L1_2_PCIPM)
1267 static ssize_t clkpm_show(struct device *dev,
1268 struct device_attribute *attr, char *buf)
1270 struct pci_dev *pdev = to_pci_dev(dev);
1271 struct pcie_link_state *link = pcie_aspm_get_link(pdev);
1273 return sprintf(buf, "%d\n", link->clkpm_enabled);
1276 static ssize_t clkpm_store(struct device *dev,
1277 struct device_attribute *attr,
1278 const char *buf, size_t len)
1280 struct pci_dev *pdev = to_pci_dev(dev);
1281 struct pcie_link_state *link = pcie_aspm_get_link(pdev);
1284 if (strtobool(buf, &state_enable) < 0)
1287 down_read(&pci_bus_sem);
1288 mutex_lock(&aspm_lock);
1290 link->clkpm_disable = !state_enable;
1291 pcie_set_clkpm(link, policy_to_clkpm_state(link));
1293 mutex_unlock(&aspm_lock);
1294 up_read(&pci_bus_sem);
1299 static DEVICE_ATTR_RW(clkpm);
1300 static DEVICE_ATTR_RW(l0s_aspm);
1301 static DEVICE_ATTR_RW(l1_aspm);
1302 static DEVICE_ATTR_RW(l1_1_aspm);
1303 static DEVICE_ATTR_RW(l1_2_aspm);
1304 static DEVICE_ATTR_RW(l1_1_pcipm);
1305 static DEVICE_ATTR_RW(l1_2_pcipm);
1307 static struct attribute *aspm_ctrl_attrs[] = {
1308 &dev_attr_clkpm.attr,
1309 &dev_attr_l0s_aspm.attr,
1310 &dev_attr_l1_aspm.attr,
1311 &dev_attr_l1_1_aspm.attr,
1312 &dev_attr_l1_2_aspm.attr,
1313 &dev_attr_l1_1_pcipm.attr,
1314 &dev_attr_l1_2_pcipm.attr,
1318 static umode_t aspm_ctrl_attrs_are_visible(struct kobject *kobj,
1319 struct attribute *a, int n)
1321 struct device *dev = kobj_to_dev(kobj);
1322 struct pci_dev *pdev = to_pci_dev(dev);
1323 struct pcie_link_state *link = pcie_aspm_get_link(pdev);
1324 static const u8 aspm_state_map[] = {
1329 ASPM_STATE_L1_1_PCIPM,
1330 ASPM_STATE_L1_2_PCIPM,
1333 if (aspm_disabled || !link)
1337 return link->clkpm_capable ? a->mode : 0;
1339 return link->aspm_capable & aspm_state_map[n - 1] ? a->mode : 0;
1342 const struct attribute_group aspm_ctrl_attr_group = {
1344 .attrs = aspm_ctrl_attrs,
1345 .is_visible = aspm_ctrl_attrs_are_visible,
1348 static int __init pcie_aspm_disable(char *str)
1350 if (!strcmp(str, "off")) {
1351 aspm_policy = POLICY_DEFAULT;
1353 aspm_support_enabled = false;
1354 printk(KERN_INFO "PCIe ASPM is disabled\n");
1355 } else if (!strcmp(str, "force")) {
1357 printk(KERN_INFO "PCIe ASPM is forcibly enabled\n");
1362 __setup("pcie_aspm=", pcie_aspm_disable);
1364 void pcie_no_aspm(void)
1367 * Disabling ASPM is intended to prevent the kernel from modifying
1368 * existing hardware state, not to clear existing state. To that end:
1369 * (a) set policy to POLICY_DEFAULT in order to avoid changing state
1370 * (b) prevent userspace from changing policy
1373 aspm_policy = POLICY_DEFAULT;
1378 bool pcie_aspm_support_enabled(void)
1380 return aspm_support_enabled;
1382 EXPORT_SYMBOL(pcie_aspm_support_enabled);