linux-kernel - [PATCH v6 1/4] PCI/ERR: Add support for resetting the Root Ports in a platform specific way

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Message-Id: <20250715-pci-port-reset-v6-1-6f9cce94e7bb@oss.qualcomm.com>
Date: Tue, 15 Jul 2025 19:51:04 +0530
From: Manivannan Sadhasivam via B4 Relay <devnull+manivannan.sadhasivam.oss.qualcomm.com@...nel.org>
To: Bjorn Helgaas <bhelgaas@...gle.com>, 
 Mahesh J Salgaonkar <mahesh@...ux.ibm.com>, 
 Oliver O'Halloran <oohall@...il.com>, Will Deacon <will@...nel.org>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kwilczynski@...nel.org>, 
 Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>, 
 Heiko Stuebner <heiko@...ech.de>, Philipp Zabel <p.zabel@...gutronix.de>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linuxppc-dev@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org, 
 linux-arm-msm@...r.kernel.org, linux-rockchip@...ts.infradead.org, 
 Niklas Cassel <cassel@...nel.org>, 
 Wilfred Mallawa <wilfred.mallawa@....com>, 
 Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>, 
 mani@...nel.org, Lukas Wunner <lukas@...ner.de>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>, 
 Manivannan Sadhasivam <mani@...nel.org>
Subject: [PATCH v6 1/4] PCI/ERR: Add support for resetting the Root Ports
 in a platform specific way

From: Manivannan Sadhasivam <mani@...nel.org>

Some host bridge devices require resetting the Root Ports in a platform
specific way to recover them from error conditions such as Fatal AER
errors, Link Down etc... So introduce pci_host_bridge::reset_root_port()
callback and call it from pcibios_reset_secondary_bus() if available. Also,
save the Root Port config space before reset and restore it afterwards.

The 'reset_root_port' callback is responsible for resetting the given Root
Port referenced by the 'pci_dev' pointer in a platform specific way and
bring it back to the working state if possible. If any error occurs during
the reset operation, relevant errno should be returned.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
---
 drivers/pci/pci.c      | 20 ++++++++++++++++++++
 drivers/pci/pcie/err.c |  5 -----
 include/linux/pci.h    |  1 +
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e9448d55113bdfd2263d8e2f6b3ec802f56b712e..b29264aa2be33b18a58b3b3db1d1fb0f6483e5e8 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4964,6 +4964,26 @@ void pci_reset_secondary_bus(struct pci_dev *dev)
 
 void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
 {
+	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
+	int ret;
+
+	if (pci_is_root_bus(dev->bus) && host->reset_root_port) {
+		/*
+		 * Save the config space of the Root Port before doing the
+		 * reset, since the state could be lost. The Endpoint state
+		 * should've been saved by the caller.
+		 */
+		pci_save_state(dev);
+		ret = host->reset_root_port(host, dev);
+		if (ret)
+			pci_err(dev, "Failed to reset Root Port: %d\n", ret);
+		else
+			/* Now restore it on success */
+			pci_restore_state(dev);
+
+		return;
+	}
+
 	pci_reset_secondary_bus(dev);
 }
 
diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
index de6381c690f5c21f00021cdc7bde8d93a5c7db52..b834fc0d705938540d3d7d3d8739770c09fe7cf1 100644
--- a/drivers/pci/pcie/err.c
+++ b/drivers/pci/pcie/err.c
@@ -234,11 +234,6 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
 	}
 
 	if (status == PCI_ERS_RESULT_NEED_RESET) {
-		/*
-		 * TODO: Should call platform-specific
-		 * functions to reset slot before calling
-		 * drivers' slot_reset callbacks?
-		 */
 		status = PCI_ERS_RESULT_RECOVERED;
 		pci_dbg(bridge, "broadcast slot_reset message\n");
 		pci_walk_bridge(bridge, report_slot_reset, &status);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 05e68f35f39238f8b9ce08df97b384d1c1e89bbe..e7c118a961910a307ec365f17b8fe4f2585267e8 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -599,6 +599,7 @@ struct pci_host_bridge {
 	void (*release_fn)(struct pci_host_bridge *);
 	int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
 	void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
+	int (*reset_root_port)(struct pci_host_bridge *bridge, struct pci_dev *dev);
 	void		*release_data;
 	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
 	unsigned int	no_ext_tags:1;		/* No Extended Tags */

-- 
2.45.2