PCI: Make link active reporting detection generic

The spec has timing requirements when waiting for a link to become active
after a conventional reset.  Implement those hard delays when waiting for
an active link so pciehp and dpc drivers don't need to duplicate this.

For devices that don't support data link layer active reporting, wait the
fixed time recommended by the PCIe spec.

Signed-off-by: Keith Busch <keith.busch@intel.com>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Sinan Kaya <okaya@kernel.org>

1 files changed, 27 insertions, 6 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6916af269b19..4b0b1d0548f0 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4489,21 +4489,42 @@ bool pcie_wait_for_link(struct pci_dev *pdev, bool active)
 	bool ret;
 	u16 lnk_status;
 
+	/*
+	 * Some controllers might not implement link active reporting. In this
+	 * case, we wait for 1000 + 100 ms.
+	 */
+	if (!pdev->link_active_reporting) {
+		msleep(1100);
+		return true;
+	}
+
+	/*
+	 * PCIe r4.0 sec 6.6.1, a component must enter LTSSM Detect within 20ms,
+	 * after which we should expect an link active if the reset was
+	 * successful. If so, software must wait a minimum 100ms before sending
+	 * configuration requests to devices downstream this port.
+	 *
+	 * If the link fails to activate, either the device was physically
+	 * removed or the link is permanently failed.
+	 */
+	if (active)
+		msleep(20);
 	for (;;) {
 		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
 		ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
 		if (ret == active)
-			return true;
+			break;
 		if (timeout <= 0)
 			break;
 		msleep(10);
 		timeout -= 10;
 	}
-
-	pci_info(pdev, "Data Link Layer Link Active not %s in 1000 msec\n",
-		 active ? "set" : "cleared");
-
-	return false;
+	if (active && ret)
+		msleep(100);
+	else if (ret != active)
+		pci_info(pdev, "Data Link Layer Link Active not %s in 1000 msec\n",
+			active ? "set" : "cleared");
+	return ret == active;
 }
 
 void pci_reset_secondary_bus(struct pci_dev *dev)