[PATCH 2/2] PCI: Wait for readiness after FLR even with Immediate Readiness

[Alexander Gruhlke]

pcie_flr() and pci_af_flr() skip pci_dev_wait() if the device advertises
Immediate Readiness.  Since commit 10baa9b4df40 ("PCI: Drop unnecessary
retries when restoring BARs"), the subsequent config restore isn't
retried, so it is lost if the device isn't ready after all.

The Samsung 990 PRO [144d:a80c] advertises Immediate Readiness but
returns ~0 for 1-7 ms after FLR, which breaks VFIO passthrough.  Keep
skipping the 100 ms delay, but call pci_dev_wait().

Fixes: 10baa9b4df40 ("PCI: Drop unnecessary retries when restoring BARs")
Link: https://bbs.archlinux.org/viewtopic.php?id=314833
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Alexander Gruhlke <gruhlke@xxxxxxxxxxx>
---
 drivers/pci/pci.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 26be5d1ca9..59856e3fdf 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4379,18 +4379,15 @@ int pcie_flr(struct pci_dev *dev)
 
 	pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_BCR_FLR);
 
-	if (dev->imm_ready)
-		goto done;
-
 	/*
 	 * Per PCIe r4.0, sec 6.6.2, a device must complete an FLR within
 	 * 100ms, but may silently discard requests while the FLR is in
 	 * progress.  Wait 100ms before trying to access the device.
 	 */
-	msleep(100);
+	if (!dev->imm_ready)
+		msleep(100);
 
 	ret = pci_dev_wait(dev, "FLR", PCIE_RESET_READY_POLL_MS);
-done:
 	pci_dev_reset_iommu_done(dev);
 	return ret;
 }
@@ -4456,19 +4453,16 @@ static int pci_af_flr(struct pci_dev *dev, bool probe)
 
 	pci_write_config_byte(dev, pos + PCI_AF_CTRL, PCI_AF_CTRL_FLR);
 
-	if (dev->imm_ready)
-		goto done;
-
 	/*
 	 * Per Advanced Capabilities for Conventional PCI ECN, 13 April 2006,
 	 * updated 27 July 2006; a device must complete an FLR within
 	 * 100ms, but may silently discard requests while the FLR is in
 	 * progress.  Wait 100ms before trying to access the device.
 	 */
-	msleep(100);
+	if (!dev->imm_ready)
+		msleep(100);
 
 	ret = pci_dev_wait(dev, "AF_FLR", PCIE_RESET_READY_POLL_MS);
-done:
 	pci_dev_reset_iommu_done(dev);
 	return ret;
 }
-- 
2.56.0