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