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From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
To: Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org,
	Lukas Wunner <lukas@wunner.de>,
	linux-kernel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>,
	linux-edac@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org,
	Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
	Oliver O'Halloran <oohall@gmail.com>,
	Tony Luck <tony.luck@intel.com>,
	=?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Subject: [PATCH 2/3] PCI: Track Flit Mode Status & print it with link status
Date: Fri, 14 Jun 2024 18:09:20 +0300
Message-Id: <20240614150921.29724-3-ilpo.jarvinen@linux.intel.com>
In-Reply-To: <20240614150921.29724-1-ilpo.jarvinen@linux.intel.com>
References: <20240614150921.29724-1-ilpo.jarvinen@linux.intel.com>
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PCIe r6.0 added Flit mode that mainly alters HW behavior but some OS
visible changes are also because of it. The OS visible changes include
differences in the layout of some capabilities and interpretation of
the TLP headers (in diagnostics situations).

To be able to determine which mode the PCIe link is using, store the
Flit Mode Status (PCIe r6.1 sec 7.5.3.20) information in addition to
the link speed into struct pci_bus in pcie_update_link_speed().

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/hotplug/pciehp_hpc.c |  5 +++--
 drivers/pci/pci.c                | 12 ++++++++----
 drivers/pci/pci.h                |  3 ++-
 drivers/pci/probe.c              |  5 +++--
 include/linux/pci.h              |  1 +
 5 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 0d818110af6d..893c022a74cb 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -291,8 +291,8 @@ static void pcie_wait_for_presence(struct pci_dev *pdev)
 int pciehp_check_link_status(struct controller *ctrl)
 {
 	struct pci_dev *pdev = ctrl_dev(ctrl);
+	u16 lnk_status, linksta2;
 	bool found;
-	u16 lnk_status;
 
 	if (!pcie_wait_for_link(pdev, true)) {
 		ctrl_info(ctrl, "Slot(%s): No link\n", slot_name(ctrl));
@@ -319,7 +319,8 @@ int pciehp_check_link_status(struct controller *ctrl)
 		return -1;
 	}
 
-	__pcie_update_link_speed(ctrl->pcie->port->subordinate, lnk_status);
+	pcie_capability_read_word(pdev, PCI_EXP_LNKSTA2, &linksta2);
+	__pcie_update_link_speed(ctrl->pcie->port->subordinate, lnk_status, linksta2);
 
 	if (!found) {
 		ctrl_info(ctrl, "Slot(%s): No device found\n",
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index db2e8f21f95c..ff47f6fdcb5a 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6164,21 +6164,25 @@ void __pcie_print_link_status(struct pci_dev *dev, bool verbose)
 	enum pci_bus_speed speed, speed_cap;
 	struct pci_dev *limiting_dev = NULL;
 	u32 bw_avail, bw_cap;
+	char *flit_mode = "";
 
 	bw_cap = pcie_bandwidth_capable(dev, &speed_cap, &width_cap);
 	bw_avail = pcie_bandwidth_available(dev, &limiting_dev, &speed, &width);
 
+	if (dev->bus && dev->bus->flit_mode)
+		flit_mode = ", in Flit mode";
+
 	if (bw_avail >= bw_cap && verbose)
-		pci_info(dev, "%u.%03u Gb/s available PCIe bandwidth (%s x%d link)\n",
+		pci_info(dev, "%u.%03u Gb/s available PCIe bandwidth (%s x%d link)%s\n",
 			 bw_cap / 1000, bw_cap % 1000,
-			 pci_speed_string(speed_cap), width_cap);
+			 pci_speed_string(speed_cap), width_cap, flit_mode);
 	else if (bw_avail < bw_cap)
-		pci_info(dev, "%u.%03u Gb/s available PCIe bandwidth, limited by %s x%d link at %s (capable of %u.%03u Gb/s with %s x%d link)\n",
+		pci_info(dev, "%u.%03u Gb/s available PCIe bandwidth, limited by %s x%d link at %s (capable of %u.%03u Gb/s with %s x%d link)%s\n",
 			 bw_avail / 1000, bw_avail % 1000,
 			 pci_speed_string(speed), width,
 			 limiting_dev ? pci_name(limiting_dev) : "<unknown>",
 			 bw_cap / 1000, bw_cap % 1000,
-			 pci_speed_string(speed_cap), width_cap);
+			 pci_speed_string(speed_cap), width_cap, flit_mode);
 }
 
 /**
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 47d8ccf6230c..54f5a1584ed8 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -298,9 +298,10 @@ enum pcie_link_width pcie_get_width_cap(struct pci_dev *dev);
 void __pcie_print_link_status(struct pci_dev *dev, bool verbose);
 void pcie_report_downtraining(struct pci_dev *dev);
 
-static inline void __pcie_update_link_speed(struct pci_bus *bus, u16 linksta)
+static inline void __pcie_update_link_speed(struct pci_bus *bus, u16 linksta, u16 linksta2)
 {
 	bus->cur_bus_speed = pcie_link_speed[linksta & PCI_EXP_LNKSTA_CLS];
+	bus->flit_mode = linksta2 & PCI_EXP_LNKSTA2_FLIT;
 }
 void pcie_update_link_speed(struct pci_bus *bus);
 
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 42dbcc401443..781b8ed892cf 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -745,10 +745,11 @@ EXPORT_SYMBOL_GPL(pci_speed_string);
 void pcie_update_link_speed(struct pci_bus *bus)
 {
 	struct pci_dev *bridge = bus->self;
-	u16 linksta;
+	u16 linksta, linksta2;
 
 	pcie_capability_read_word(bridge, PCI_EXP_LNKSTA, &linksta);
-	__pcie_update_link_speed(bus, linksta);
+	pcie_capability_read_word(bridge, PCI_EXP_LNKSTA2, &linksta2);
+	__pcie_update_link_speed(bus, linksta, linksta2);
 }
 EXPORT_SYMBOL_GPL(pcie_update_link_speed);
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index d21c704aaffa..a67294042bc5 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -680,6 +680,7 @@ struct pci_bus {
 	struct bin_attribute	*legacy_mem;	/* Legacy mem */
 	unsigned int		is_added:1;
 	unsigned int		unsafe_warn:1;	/* warned about RW1C config write */
+	bool			flit_mode;	/* Link in Flit mode */
 };
 
 #define to_pci_bus(n)	container_of(n, struct pci_bus, dev)
-- 
2.39.2