+/* PCI registers */
+#define PCI_CFG_RETRY_TIMEOUT 0x041
+#define PCI_CFG_LINK_CTRL_VAL_L0S_EN 0x01
+#define PCI_CFG_LINK_CTRL_VAL_L1_EN 0x02
+
+static u16 iwl_pciexp_link_ctrl(struct iwl_trans *trans)
+{
+ int pos;
+ u16 pci_lnk_ctl;
+ struct iwl_trans_pcie *trans_pcie =
+ IWL_TRANS_GET_PCIE_TRANS(trans);
+
+ struct pci_dev *pci_dev = trans_pcie->pci_dev;
+
+ pos = pci_pcie_cap(pci_dev);
+ pci_read_config_word(pci_dev, pos + PCI_EXP_LNKCTL, &pci_lnk_ctl);
+ return pci_lnk_ctl;
+}
+
+static void iwl_apm_config(struct iwl_trans *trans)
+{
+ /*
+ * HW bug W/A for instability in PCIe bus L0S->L1 transition.
+ * Check if BIOS (or OS) enabled L1-ASPM on this device.
+ * If so (likely), disable L0S, so device moves directly L0->L1;
+ * costs negligible amount of power savings.
+ * If not (unlikely), enable L0S, so there is at least some
+ * power savings, even without L1.
+ */
+ u16 lctl = iwl_pciexp_link_ctrl(trans);
+
+ if ((lctl & PCI_CFG_LINK_CTRL_VAL_L1_EN) ==
+ PCI_CFG_LINK_CTRL_VAL_L1_EN) {
+ /* L1-ASPM enabled; disable(!) L0S */
+ iwl_set_bit(trans, CSR_GIO_REG, CSR_GIO_REG_VAL_L0S_ENABLED);
+ dev_printk(KERN_INFO, trans->dev,
+ "L1 Enabled; Disabling L0S\n");
+ } else {
+ /* L1-ASPM disabled; enable(!) L0S */
+ iwl_clear_bit(trans, CSR_GIO_REG, CSR_GIO_REG_VAL_L0S_ENABLED);
+ dev_printk(KERN_INFO, trans->dev,
+ "L1 Disabled; Enabling L0S\n");
+ }
+}
+