1 // SPDX-License-Identifier: ISC
2 /*
3 * Copyright (C) 2019 Lorenzo Bianconi <lorenzo@kernel.org>
4 */
5
6 #include <linux/pci.h>
7
mt76_pci_disable_aspm(struct pci_dev * pdev)8 void mt76_pci_disable_aspm(struct pci_dev *pdev)
9 {
10 struct pci_dev *parent = pdev->bus->self;
11 u16 aspm_conf, parent_aspm_conf = 0;
12
13 pcie_capability_read_word(pdev, PCI_EXP_LNKCTL, &aspm_conf);
14 aspm_conf &= PCI_EXP_LNKCTL_ASPMC;
15 if (parent) {
16 pcie_capability_read_word(parent, PCI_EXP_LNKCTL,
17 &parent_aspm_conf);
18 parent_aspm_conf &= PCI_EXP_LNKCTL_ASPMC;
19 }
20
21 if (!aspm_conf && (!parent || !parent_aspm_conf)) {
22 /* aspm already disabled */
23 return;
24 }
25
26 dev_info(&pdev->dev, "disabling ASPM %s %s\n",
27 (aspm_conf & PCI_EXP_LNKCTL_ASPM_L0S) ? "L0s" : "",
28 (aspm_conf & PCI_EXP_LNKCTL_ASPM_L1) ? "L1" : "");
29
30 if (IS_ENABLED(CONFIG_PCIEASPM)) {
31 int err;
32
33 err = pci_disable_link_state(pdev, aspm_conf);
34 if (!err)
35 return;
36 }
37
38 /* both device and parent should have the same ASPM setting.
39 * disable ASPM in downstream component first and then upstream.
40 */
41 pcie_capability_clear_word(pdev, PCI_EXP_LNKCTL, aspm_conf);
42 if (parent)
43 pcie_capability_clear_word(parent, PCI_EXP_LNKCTL,
44 aspm_conf);
45 }
46 EXPORT_SYMBOL_GPL(mt76_pci_disable_aspm);
47