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Date:   Sun, 11 Jun 2023 18:20:02 +0100 (BST)
From:   "Maciej W. Rozycki" <macro@orcam.me.uk>
To:     Bjorn Helgaas <bhelgaas@google.com>,
        Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        Oliver O'Halloran <oohall@gmail.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Saeed Mahameed <saeedm@nvidia.com>,
        Leon Romanovsky <leon@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
cc:     Alex Williamson <alex.williamson@redhat.com>,
        Lukas Wunner <lukas@wunner.de>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Stefan Roese <sr@denx.de>, Jim Wilson <wilson@tuliptree.org>,
        David Abdurachmanov <david.abdurachmanov@gmail.com>,
        =?UTF-8?Q?Pali_Roh=C3=A1r?= <pali@kernel.org>,
        linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-rdma@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v9 12/14] PCI: Provide stub failed link recovery for device
 probing and hot plug
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This now fails unconditionally and will be always optimised away, but 
provides for quirks to implement recovery for failed links detected in 
device probing and device hot plug events.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
---
New change in v9, factored out from 7/7:

- Rename `pcie_downstream_link_retrain' to `pcie_failed_link_retrain'.

- Add stub implementation in "pci.h".
---
 drivers/pci/pci.c   |    2 ++
 drivers/pci/pci.h   |    4 ++++
 drivers/pci/probe.c |    2 ++
 3 files changed, 8 insertions(+)

linux-pcie-failed-link-retrain.diff
Index: linux-macro/drivers/pci/pci.c
===================================================================
--- linux-macro.orig/drivers/pci/pci.c
+++ linux-macro/drivers/pci/pci.c
@@ -4912,6 +4912,8 @@ static bool pcie_wait_for_link_delay(str
 	if (active)
 		msleep(20);
 	ret = pcie_wait_for_link_status(pdev, false, active);
+	if (active && !ret)
+		ret = pcie_failed_link_retrain(pdev);
 	if (active && ret)
 		msleep(delay);
 
Index: linux-macro/drivers/pci/pci.h
===================================================================
--- linux-macro.orig/drivers/pci/pci.h
+++ linux-macro/drivers/pci/pci.h
@@ -554,6 +554,10 @@ static inline int pci_dev_specific_disab
 	return -ENOTTY;
 }
 #endif
+static inline bool pcie_failed_link_retrain(struct pci_dev *dev)
+{
+	return false;
+}
 
 /* PCI error reporting and recovery */
 pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
Index: linux-macro/drivers/pci/probe.c
===================================================================
--- linux-macro.orig/drivers/pci/probe.c
+++ linux-macro/drivers/pci/probe.c
@@ -2549,6 +2549,8 @@ void pci_device_add(struct pci_dev *dev,
 	dma_set_max_seg_size(&dev->dev, 65536);
 	dma_set_seg_boundary(&dev->dev, 0xffffffff);
 
+	pcie_failed_link_retrain(dev);
+
 	/* Fix up broken headers */
 	pci_fixup_device(pci_fixup_header, dev);