PCI/PM: Shorten pci_bridge_wait_for_secondary_bus() wait time for slow links

With slow links (<= 5GT/s) active link reporting is not mandatory, so if a
device is disconnected during system sleep we might end up waiting for it
to respond for ~60s, which slows down resume time.

PCIe r6.0, sec 6.6.1, mandates that software must wait for at least 1s
before it can assume a device is broken, so use that minimum requirement
for slow links and bail out if the device doesn't respond within 1s.
However, if the port supports active link reporting we can wait longer as
we do with the fast links.

This should make system resume time faster for slow links as well while
still following the PCIe spec.

While there move the PCI_RESET_WAIT constant into pci.c because it is
not used outside of that file anymore.

Link: https://lore.kernel.org/r/20230425064751.24951-1-mika.westerberg@linux.intel.com
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

1 files changed, 37 insertions, 12 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 5ede93222bc1..578bf0d3ec3c 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -65,6 +65,13 @@ struct pci_pme_device {
 #define PME_TIMEOUT 1000 /* How long between PME checks */
 
 /*
+ * Following exit from Conventional Reset, devices must be ready within 1 sec
+ * (PCIe r6.0 sec 6.6.1).  A D3cold to D0 transition implies a Conventional
+ * Reset (PCIe r6.0 sec 5.8).
+ */
+#define PCI_RESET_WAIT 1000 /* msec */
+
+/*
  * Devices may extend the 1 sec period through Request Retry Status
  * completions (PCIe r6.0 sec 2.3.1).  The spec does not provide an upper
  * limit, but 60 sec ought to be enough for any device to become
@@ -5011,11 +5018,9 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type)
 	 *
 	 * However, 100 ms is the minimum and the PCIe spec says the
 	 * software must allow at least 1s before it can determine that the
-	 * device that did not respond is a broken device. There is
-	 * evidence that 100 ms is not always enough, for example certain
-	 * Titan Ridge xHCI controller does not always respond to
-	 * configuration requests if we only wait for 100 ms (see
-	 * https://bugzilla.kernel.org/show_bug.cgi?id=203885).
+	 * device that did not respond is a broken device. Also device can
+	 * take longer than that to respond if it indicates so through Request
+	 * Retry Status completions.
 	 *
 	 * Therefore we wait for 100 ms and check for the device presence
 	 * until the timeout expires.
@@ -5024,16 +5029,36 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type)
 		return 0;
 
 	if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) {
+		u16 status;
+
 		pci_dbg(dev, "waiting %d ms for downstream link\n", delay);
 		msleep(delay);
-	} else {
-		pci_dbg(dev, "waiting %d ms for downstream link, after activation\n",
-			delay);
-		if (!pcie_wait_for_link_delay(dev, true, delay)) {
-			/* Did not train, no need to wait any further */
-			pci_info(dev, "Data Link Layer Link Active not set in 1000 msec\n");
+
+		if (!pci_dev_wait(child, reset_type, PCI_RESET_WAIT - delay))
+			return 0;
+
+		/*
+		 * If the port supports active link reporting we now check
+		 * whether the link is active and if not bail out early with
+		 * the assumption that the device is not present anymore.
+		 */
+		if (!dev->link_active_reporting)
 			return -ENOTTY;
-		}
+
+		pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &status);
+		if (!(status & PCI_EXP_LNKSTA_DLLLA))
+			return -ENOTTY;
+
+		return pci_dev_wait(child, reset_type,
+				    PCIE_RESET_READY_POLL_MS - PCI_RESET_WAIT);
+	}
+
+	pci_dbg(dev, "waiting %d ms for downstream link, after activation\n",
+		delay);
+	if (!pcie_wait_for_link_delay(dev, true, delay)) {
+		/* Did not train, no need to wait any further */
+		pci_info(dev, "Data Link Layer Link Active not set in 1000 msec\n");
+		return -ENOTTY;
 	}
 
 	return pci_dev_wait(child, reset_type,