linux-kernel - [PATCH v2 06/10] PCI: Cache PCIe device's Supported Speed Vector

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Date:   Fri, 15 Sep 2023 15:01:38 +0300
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     linux-pci@...r.kernel.org, Bjorn Helgaas <helgaas@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Lukas Wunner <lukas@...ner.de>,
        Alexandru Gagniuc <mr.nuke.me@...il.com>,
        Krishna chaitanya chundru <quic_krichai@...cinc.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-kernel@...r.kernel.org
Cc:     Alex Deucher <alexdeucher@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: [PATCH v2 06/10] PCI: Cache PCIe device's Supported Speed Vector

The Supported Link Speeds Vector in the Link Capabilities Register 2
corresponds to the bus below on Root Ports and Downstream Ports,
whereas it corresponds to the bus above on Upstream Ports and
Endpoints. Only the former is currently cached in pcie_bus_speeds in
the struct pci_bus. The link speeds that are supported is the
intersection of these two.

Store the device's Supported Link Speeds Vector into the struct pci_bus
when the Function 0 is enumerated (the Multi-Function Devices must have
same speeds the same for all Functions) to be easily able to calculate
the intersection of Supported Link Speeds.

Suggested-by: Lukas Wunner <lukas@...ner.de>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
---
 drivers/pci/probe.c  | 10 ++++++++++
 drivers/pci/remove.c |  2 ++
 include/linux/pci.h  |  1 +
 3 files changed, 13 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ca1d797a30cb..a9408f2420e5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2564,6 +2564,7 @@ static void pci_set_msi_domain(struct pci_dev *dev)
 
 void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 {
+	u8 dev_speeds = 0;
 	int ret;
 
 	pci_configure_device(dev);
@@ -2590,11 +2591,20 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 
 	pci_init_capabilities(dev);
 
+	if (pci_is_pcie(dev) && PCI_FUNC(dev->devfn) == 0) {
+		u32 linkcap, linkcap2;
+
+		pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &linkcap);
+		pcie_capability_read_dword(dev, PCI_EXP_LNKCAP2, &linkcap2);
+		dev_speeds = pcie_get_supported_speeds(linkcap, linkcap2);
+	}
 	/*
 	 * Add the device to our list of discovered devices
 	 * and the bus list for fixup functions, etc.
 	 */
 	down_write(&pci_bus_sem);
+	if (dev_speeds)
+		bus->pcie_dev_speeds = dev_speeds;
 	list_add_tail(&dev->bus_list, &bus->devices);
 	up_write(&pci_bus_sem);
 
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index d749ea8250d6..656784cfb291 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -36,6 +36,8 @@ static void pci_destroy_dev(struct pci_dev *dev)
 	device_del(&dev->dev);
 
 	down_write(&pci_bus_sem);
+	if (pci_is_pcie(dev) && PCI_FUNC(dev->devfn) == 0)
+		dev->bus->pcie_dev_speeds = 0;
 	list_del(&dev->bus_list);
 	up_write(&pci_bus_sem);
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index cb03f3ff9d23..b8bd3dc92032 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -665,6 +665,7 @@ struct pci_bus {
 	unsigned char	max_bus_speed;	/* enum pci_bus_speed */
 	unsigned char	cur_bus_speed;	/* enum pci_bus_speed */
 	u8		pcie_bus_speeds;/* Supported Link Speeds Vector (+ reserved 0 at LSB) */
+	u8		pcie_dev_speeds;/* Device's Supported Link Speeds Vector (+ 0 at LSB) */
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
 	int		domain_nr;
 #endif
-- 
2.30.2