linux-kernel - [PATCH V1] PCI: Clear errors logged in Secondary Status Register

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Message-ID: <20240104013229.693041-1-vidyas@nvidia.com>
Date: Thu, 4 Jan 2024 07:02:29 +0530
From: Vidya Sagar <vidyas@...dia.com>
To: <bhelgaas@...gle.com>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<treding@...dia.com>, <jonathanh@...dia.com>, <kthota@...dia.com>,
	<mmaddireddy@...dia.com>, <vidyas@...dia.com>, <sagar.tv@...il.com>
Subject: [PATCH V1] PCI: Clear errors logged in Secondary Status Register

If a downstream port has a PCIe switch connected to it, the enumeration
process leaves the 'Received Master Abort' bit set in the Secondary
Status Register of the downstream port because of the Unsupported
Requests (URs) take place in the downstream hierarchy. Since the
ownership of Secondary Status Register always lies with the OS including
systems with Firmware-First approach for error handling[1], clear the
error status bits in the Secondary Status Register post enumeration.

[1] https://lore.kernel.org/all/1fb9d746-0695-4d19-af98-f442f31cd464@nvidia.com/T/

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
 drivers/pci/probe.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 43159965e09e..edf8202465d8 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1470,6 +1470,9 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 	}

 out:
+	/* Clear errors in the Secondary Status Register */
+	pci_write_config_word(dev, PCI_SEC_STATUS, 0xffff);
+
 	pci_write_config_word(dev, PCI_BRIDGE_CONTROL, bctl);

 	pm_runtime_put(&dev->dev);
-- 
2.25.1