1 // SPDX-License-Identifier: ISC
2 /*
3  * Copyright (C) 2019 Lorenzo Bianconi <lorenzo@kernel.org>
4  */
5 
6 #include "mt76.h"
7 #include <linux/pci.h>
8 
9 void mt76_pci_disable_aspm(struct pci_dev *pdev)
10 {
11 	struct pci_dev *parent = pdev->bus->self;
12 	u16 aspm_conf, parent_aspm_conf = 0;
13 
14 	pcie_capability_read_word(pdev, PCI_EXP_LNKCTL, &aspm_conf);
15 	aspm_conf &= PCI_EXP_LNKCTL_ASPMC;
16 	if (parent) {
17 		pcie_capability_read_word(parent, PCI_EXP_LNKCTL,
18 					  &parent_aspm_conf);
19 		parent_aspm_conf &= PCI_EXP_LNKCTL_ASPMC;
20 	}
21 
22 	if (!aspm_conf && (!parent || !parent_aspm_conf)) {
23 		/* aspm already disabled */
24 		return;
25 	}
26 
27 	dev_info(&pdev->dev, "disabling ASPM %s %s\n",
28 		 (aspm_conf & PCI_EXP_LNKCTL_ASPM_L0S) ? "L0s" : "",
29 		 (aspm_conf & PCI_EXP_LNKCTL_ASPM_L1) ? "L1" : "");
30 
31 	if (IS_ENABLED(CONFIG_PCIEASPM)) {
32 		int err;
33 
34 		err = pci_disable_link_state(pdev, aspm_conf);
35 		if (!err)
36 			return;
37 	}
38 
39 	/* both device and parent should have the same ASPM setting.
40 	 * disable ASPM in downstream component first and then upstream.
41 	 */
42 	pcie_capability_clear_word(pdev, PCI_EXP_LNKCTL, aspm_conf);
43 	if (parent)
44 		pcie_capability_clear_word(parent, PCI_EXP_LNKCTL,
45 					   aspm_conf);
46 }
47 EXPORT_SYMBOL_GPL(mt76_pci_disable_aspm);
48