FAILED: patch "[PATCH] PCI: Always lift 2.5GT/s restriction in PCIe failed link" failed to apply to 6.12-stable tree

PATCH Applied [email protected] 3 participants 3 messages Jul 13 – Jul 15

Subsystems (2)

Stable branch PCI

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author maintainer

2026-07-13 13:26 UTC #0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 72780f7964684939d7d2f69c348876213b184484
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026071351-deport-apply-58df@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 72780f7964684939d7d2f69c348876213b184484 Mon Sep 17 00:00:00 2001
From: "Maciej W. Rozycki" <[email protected]>
Date: Mon, 8 Dec 2025 19:24:29 +0000
Subject: [PATCH] PCI: Always lift 2.5GT/s restriction in PCIe failed link
retraining

Discard Vendor:Device ID matching in the PCIe failed link retraining quirk and ignore the link status for the removal of the 2.5GT/s speed clamp, whether applied by the quirk itself or the firmware earlier on. Revert to the original target link speed if this final link retraining has failed.

This is so that link training noise in hot-plug scenarios does not make a link remain clamped to the 2.5GT/s speed where an event race has led the quirk to apply the speed clamp for one device, only to leave it in place for a subsequent device to be plugged in.

Refer to the Link Capabilities register directly for the maximum link speed determination so as to streamline backporting.

Fixes a89c82249c37 ("PCI: Work around PCIe link training failures")

Signed-off-by Maciej W. Rozycki <[email protected]>

Signed-off-by Bjorn Helgaas <[email protected]>

Tested-by Alok Tiwari <[email protected]>

Cc [email protected] # v6.5+

Link https://patch.msgid.link/[email protected] open here

drivers/pci/quirks.c +18 ~~-33~~

index caaed1a01dc0..dd0025d3914e 100644
@@ -80,11 +80,10 @@ static bool pcie_lbms_seen(struct pci_dev *dev, u16 lnksta)
  * Restrict the speed to 2.5GT/s then with the Target Link Speed field,
  * request a retrain and check the result.
  *
- * If this turns out successful and we know by the Vendor:Device ID it is
- * safe to do so, then lift the restriction, letting the devices negotiate
- * a higher speed.  Also check for a similar 2.5GT/s speed restriction the
- * firmware may have already arranged and lift it with ports that already
- * report their data link being up.
+ * If this turns out successful, or where a 2.5GT/s speed restriction has
+ * been previously arranged by the firmware and the port reports its link
+ * already being up, lift the restriction, in a hope it is safe to do so,
+ * letting the devices negotiate a higher speed.
  *
  * Otherwise revert the speed to the original setting and request a retrain
  * again to remove any residual state, ignoring the result as it's supposed

@@ -95,51 +94,37 @@ static bool pcie_lbms_seen(struct pci_dev *dev, u16 lnksta)
  */
 int pcie_failed_link_retrain(struct pci_dev *dev)
 {
-	static const struct pci_device_id ids[] = {
-		{ PCI_VDEVICE(ASMEDIA, 0x2824) }, /* ASMedia ASM2824 */
-		{}
-	};
-	u16 lnksta, lnkctl2;
+	u16 lnksta, lnkctl2, oldlnkctl2;
 	int ret = -ENOTTY;
+	u32 lnkcap;
 
 	if (!pci_is_pcie(dev) || !pcie_downstream_port(dev) ||
 	    !pcie_cap_has_lnkctl2(dev) || !dev->link_active_reporting)
 		return ret;
 
 	pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
+	pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &oldlnkctl2);
 	if (!(lnksta & PCI_EXP_LNKSTA_DLLLA) && pcie_lbms_seen(dev, lnksta)) {
-		u16 oldlnkctl2;
-
 		pci_info(dev, "broken device, retraining non-functional downstream link at 2.5GT/s\n");
-
-		pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &oldlnkctl2);
 		ret = pcie_set_target_speed(dev, PCIE_SPEED_2_5GT, false);
-		if (ret) {
-			pci_info(dev, "retraining failed\n");
-			pcie_set_target_speed(dev, PCIE_LNKCTL2_TLS2SPEED(oldlnkctl2),
-					      true);
-			return ret;
-		}
-
-		pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
+		if (ret)
+			goto err;
 	}
 
 	pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &lnkctl2);
-
-	if ((lnksta & PCI_EXP_LNKSTA_DLLLA) &&
-	    (lnkctl2 & PCI_EXP_LNKCTL2_TLS) == PCI_EXP_LNKCTL2_TLS_2_5GT &&
-	    pci_match_id(ids, dev)) {
-		u32 lnkcap;
-
+	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
+	if ((lnkctl2 & PCI_EXP_LNKCTL2_TLS) == PCI_EXP_LNKCTL2_TLS_2_5GT &&
+	    (lnkcap & PCI_EXP_LNKCAP_SLS) != PCI_EXP_LNKCAP_SLS_2_5GB) {
 		pci_info(dev, "removing 2.5GT/s downstream link speed restriction\n");
-		pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
 		ret = pcie_set_target_speed(dev, PCIE_LNKCAP_SLS2SPEED(lnkcap), false);
-		if (ret) {
-			pci_info(dev, "retraining failed\n");
-			return ret;
-		}
+		if (ret)
+			goto err;
 	}
 
+	return ret;
+err:
+	pci_info(dev, "retraining failed\n");
+	pcie_set_target_speed(dev, PCIE_LNKCTL2_TLS2SPEED(oldlnkctl2), true);
 	return ret;
 }

Maciej W. Rozycki

2026-07-13 22:26 UTC #1 lore raw

PATCH 1/1 PCI: Always lift 2.5GT/s restriction in PCIe failed link retraining

commit 72780f7964684939d7d2f69c348876213b184484 upstream.

Refer to the Link Capabilities register directly for the maximum link speed determination so as to streamline backporting.

Fixes a89c82249c37 ("PCI: Work around PCIe link training failures")

Signed-off-by Maciej W. Rozycki <[email protected]>

Signed-off-by Bjorn Helgaas <[email protected]>

Tested-by Alok Tiwari <[email protected]>

Cc [email protected] # v6.5+

Link https://patch.msgid.link/[email protected] open here

[ Update for missing PCIe link speed helpers for 6.12.y. ]

Signed-off-by Maciej W. Rozycki <[email protected]>

---
 drivers/pci/quirks.c | 51 +++++++++++++++++---------------------------
 1 file changed, 20 insertions(+), 31 deletions(-)

drivers/pci/quirks.c +20 ~~-31~~

index 3d05ea35c536..9b2acf388f8a 100644
@@ -68,11 +68,10 @@
  * Restrict the speed to 2.5GT/s then with the Target Link Speed field,
  * request a retrain and check the result.
  *
- * If this turns out successful and we know by the Vendor:Device ID it is
- * safe to do so, then lift the restriction, letting the devices negotiate
- * a higher speed.  Also check for a similar 2.5GT/s speed restriction the
- * firmware may have already arranged and lift it with ports that already
- * report their data link being up.
+ * If this turns out successful, or where a 2.5GT/s speed restriction has
+ * been previously arranged by the firmware and the port reports its link
+ * already being up, lift the restriction, in a hope it is safe to do so,
+ * letting the devices negotiate a higher speed.
  *
  * Otherwise revert the speed to the original setting and request a retrain
  * again to remove any residual state, ignoring the result as it's supposed

@@ -83,12 +82,9 @@
  */
 int pcie_failed_link_retrain(struct pci_dev *dev)
 {
-	static const struct pci_device_id ids[] = {
-		{ PCI_VDEVICE(ASMEDIA, 0x2824) }, /* ASMedia ASM2824 */
-		{}
-	};
-	u16 lnksta, lnkctl2;
+	u16 lnksta, lnkctl2, oldlnkctl2;
 	int ret = -ENOTTY;
+	u32 lnkcap;
 
 	if (!pci_is_pcie(dev) || !pcie_downstream_port(dev) ||
 	    !pcie_cap_has_lnkctl2(dev) || !dev->link_active_reporting)

@@ -96,10 +92,9 @@ int pcie_failed_link_retrain(struct pci_dev *dev)
 
 	pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &lnkctl2);
 	pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
+	oldlnkctl2 = lnkctl2;
 	if ((lnksta & (PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_DLLLA)) ==
 	    PCI_EXP_LNKSTA_LBMS) {
-		u16 oldlnkctl2 = lnkctl2;
-
 		pci_info(dev, "broken device, retraining non-functional downstream link at 2.5GT/s\n");
 
 		lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;

@@ -107,35 +102,29 @@ int pcie_failed_link_retrain(struct pci_dev *dev)
 		pcie_capability_write_word(dev, PCI_EXP_LNKCTL2, lnkctl2);
 
 		ret = pcie_retrain_link(dev, false);
-		if (ret) {
-			pci_info(dev, "retraining failed\n");
-			pcie_capability_write_word(dev, PCI_EXP_LNKCTL2,
-						   oldlnkctl2);
-			pcie_retrain_link(dev, true);
-			return ret;
-		}
-
-		pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
+		if (ret)
+			goto err;
 	}
 
-	if ((lnksta & PCI_EXP_LNKSTA_DLLLA) &&
-	    (lnkctl2 & PCI_EXP_LNKCTL2_TLS) == PCI_EXP_LNKCTL2_TLS_2_5GT &&
-	    pci_match_id(ids, dev)) {
-		u32 lnkcap;
-
+	pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
+	if ((lnkctl2 & PCI_EXP_LNKCTL2_TLS) == PCI_EXP_LNKCTL2_TLS_2_5GT &&
+	    (lnkcap & PCI_EXP_LNKCAP_SLS) != PCI_EXP_LNKCAP_SLS_2_5GB) {
 		pci_info(dev, "removing 2.5GT/s downstream link speed restriction\n");
-		pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
 		lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
 		lnkctl2 |= lnkcap & PCI_EXP_LNKCAP_SLS;
 		pcie_capability_write_word(dev, PCI_EXP_LNKCTL2, lnkctl2);
 
 		ret = pcie_retrain_link(dev, false);
-		if (ret) {
-			pci_info(dev, "retraining failed\n");
-			return ret;
-		}
+		if (ret)
+			goto err;
 	}
 
+	return ret;
+err:
+	pci_info(dev, "retraining failed\n");
+	pcie_capability_write_word(dev, PCI_EXP_LNKCTL2, oldlnkctl2);
+
+	pcie_retrain_link(dev, true);
 	return ret;
 }

Signature · 1 line

2.20.1

Sasha Levin

maintainer Applied

2026-07-15 00:12 UTC #2 lore raw

Re: [PATCH 6.12.y] PCI: Always lift 2.5GT/s restriction in PCIe failed link retraining

Quoted 3 lines

Discard Vendor:Device ID matching in the PCIe failed link retraining quirk and ignore the link status for the removal of the 2.5GT/s speed clamp, whether applied by the quirk itself or the firmware earlier on.

Queued for 6.12, thanks.

Signature · 2 lines

Thanks,
Sasha