1// SPDX-License-Identifier: ISC
 2/*
 3 * Copyright (C) 2019 Lorenzo Bianconi <lorenzo@kernel.org>
 4 */
 5
 6#include <linux/pci.h>
 7
 8void 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}
46EXPORT_SYMBOL_GPL(mt76_pci_disable_aspm);