[PATCH] PCI: Stop waiting for link status after config read failure

[Yury Murashka <yurypm@arista.com>]

With a nested PCIe topology with multiple layers of hotplug, a link can go
down near the bottom of the topology shortly before a link above it goes
down. In that case, pcie_wait_for_link_status() can wait for the full
timeout while every read of the link status register fails because the
device has disappeared.

Return immediately when reading the link status fails so event processing
can continue.

Signed-off-by: Yury Murashka <yurypm@arista.com>
Co-authored-by: James Sewart <jamessewart@arista.com>
---
 drivers/pci/pci.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b2879a6be..a568d5ac1 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4565,8 +4565,9 @@ static int pci_pm_reset(struct pci_dev *dev, bool probe)
  * @use_lt: Use the LT bit if TRUE, or the DLLLA bit if FALSE.
  * @active: Waiting for active or inactive?
  *
- * Return 0 if successful, or -ETIMEDOUT if status has not changed within
- * PCIE_LINK_RETRAIN_TIMEOUT_MS milliseconds.
+ * Return 0 if successful, -ENODEV if the link status cannot be read, or
+ * -ETIMEDOUT if status has not changed within PCIE_LINK_RETRAIN_TIMEOUT_MS
+ * milliseconds.
  */
 static int pcie_wait_for_link_status(struct pci_dev *pdev,
 				     bool use_lt, bool active)
@@ -4580,7 +4581,8 @@ static int pcie_wait_for_link_status(struct pci_dev *pdev,
 
 	end_jiffies = jiffies + msecs_to_jiffies(PCIE_LINK_RETRAIN_TIMEOUT_MS);
 	do {
-		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta);
+		if (pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta))
+			return -ENODEV;
 		if ((lnksta & lnksta_mask) == lnksta_match)
 			return 0;
 		msleep(1);
@@ -4603,8 +4605,9 @@ static int pcie_wait_for_link_status(struct pci_dev *pdev,
  * according to @use_lt.  It is not verified whether the use of the DLLLA
  * bit is valid.
  *
- * Return 0 if successful, or -ETIMEDOUT if training has not completed
- * within PCIE_LINK_RETRAIN_TIMEOUT_MS milliseconds.
+ * Return 0 if successful, -ENODEV if the link status cannot be read, or
+ * -ETIMEDOUT if training has not completed within
+ * PCIE_LINK_RETRAIN_TIMEOUT_MS milliseconds.
  */
 int pcie_retrain_link(struct pci_dev *pdev, bool use_lt)
 {

base-commit: a500db7819c50db59e55f1b4fa1c3baa5a2616f3
-- 
2.51.0