PCI: Get rid of dev->has_secondary_link flag

In some systems, the Device/Port Type in the PCI Express Capabilities
register incorrectly identifies upstream ports as downstream ports.

d0751b98df ("PCI: Add dev->has_secondary_link to track downstream PCIe
links") addressed this by adding pci_dev.has_secondary_link, which is set
for downstream ports.  But this is confusing because pci_pcie_type()
sometimes gives the wrong answer, and it's not obvious that we should use
pci_dev.has_secondary_link instead.

Reduce the confusion by correcting the type of the port itself so that
pci_pcie_type() returns the actual type regardless of what the Device/Port
Type register claims it is.  Update the users to call pci_pcie_type() and
pcie_downstream_port() accordingly, and remove pci_dev.has_secondary_link
completely.

Link: https://lore.kernel.org/linux-pci/20190703133953.GK128603@google.com/
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20190822085553.62697-2-mika.westerberg@linux.intel.com
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/pci/pci.c

@@ -3576,7 +3576,7 @@ int pci_enable_atomic_ops_to_root(struct pci_dev *dev, u32 cap_mask)
 		}
 
 		/* Ensure upstream ports don't block AtomicOps on egress */
-		if (!bridge->has_secondary_link) {
+		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_UPSTREAM) {
 			pcie_capability_read_dword(bridge, PCI_EXP_DEVCTL2,
 						   &ctl2);
 			if (ctl2 & PCI_EXP_DEVCTL2_ATOMIC_EGRESS_BLOCK)

drivers/pci/pcie/aspm.c

@@ -913,10 +913,10 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
 
 	/*
 	 * We allocate pcie_link_state for the component on the upstream
-	 * end of a Link, so there's nothing to do unless this device has a
-	 * Link on its secondary side.
+	 * end of a Link, so there's nothing to do unless this device is
+	 * downstream port.
 	 */
-	if (!pdev->has_secondary_link)
+	if (!pcie_downstream_port(pdev))
 		return;
 
 	/* VIA has a strange chipset, root port is under a bridge */
@@ -1070,7 +1070,7 @@ static int __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
 	if (!pci_is_pcie(pdev))
 		return 0;
 
-	if (pdev->has_secondary_link)
+	if (pcie_downstream_port(pdev))
 		parent = pdev;
 	if (!parent || !parent->link_state)
 		return -EINVAL;

drivers/pci/pcie/err.c

@@ -166,7 +166,7 @@ static pci_ers_result_t reset_link(struct pci_dev *dev, u32 service)
 	driver = pcie_port_find_service(dev, service);
 	if (driver && driver->reset_link) {
 		status = driver->reset_link(dev);
-	} else if (dev->has_secondary_link) {
+	} else if (pcie_downstream_port(dev)) {
 		status = default_reset_link(dev);
 	} else {
 		pci_printk(KERN_DEBUG, dev, "no link-reset support at upstream device %s\n",

drivers/pci/probe.c

@@ -1431,26 +1431,38 @@ void set_pcie_port_type(struct pci_dev *pdev)
 	pci_read_config_word(pdev, pos + PCI_EXP_DEVCAP, &reg16);
 	pdev->pcie_mpss = reg16 & PCI_EXP_DEVCAP_PAYLOAD;
 
-	/*
-	 * A Root Port or a PCI-to-PCIe bridge is always the upstream end
-	 * of a Link.  No PCIe component has two Links.  Two Links are
-	 * connected by a Switch that has a Port on each Link and internal
-	 * logic to connect the two Ports.
-	 */
-	type = pci_pcie_type(pdev);
-	if (type == PCI_EXP_TYPE_ROOT_PORT ||
-	    type == PCI_EXP_TYPE_PCIE_BRIDGE)
-		pdev->has_secondary_link = 1;
-	else if (type == PCI_EXP_TYPE_UPSTREAM ||
-		 type == PCI_EXP_TYPE_DOWNSTREAM) {
 	parent = pci_upstream_bridge(pdev);
+	if (!parent)
+		return;
 
 	/*
-		 * Usually there's an upstream device (Root Port or Switch
-		 * Downstream Port), but we can't assume one exists.
+	 * Some systems do not identify their upstream/downstream ports
+	 * correctly so detect impossible configurations here and correct
+	 * the port type accordingly.
 	 */
-		if (parent && !parent->has_secondary_link)
-			pdev->has_secondary_link = 1;
+	type = pci_pcie_type(pdev);
+	if (type == PCI_EXP_TYPE_DOWNSTREAM) {
+		/*
+		 * If pdev claims to be downstream port but the parent
+		 * device is also downstream port assume pdev is actually
+		 * upstream port.
+		 */
+		if (pcie_downstream_port(parent)) {
+			pci_info(pdev, "claims to be downstream port but is acting as upstream port, correcting type\n");
+			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
+			pdev->pcie_flags_reg |= PCI_EXP_TYPE_UPSTREAM;
+		}
+	} else if (type == PCI_EXP_TYPE_UPSTREAM) {
+		/*
+		 * If pdev claims to be upstream port but the parent
+		 * device is also upstream port assume pdev is actually
+		 * downstream port.
+		 */
+		if (pci_pcie_type(parent) == PCI_EXP_TYPE_UPSTREAM) {
+			pci_info(pdev, "claims to be upstream port but is acting as downstream port, correcting type\n");
+			pdev->pcie_flags_reg &= ~PCI_EXP_FLAGS_TYPE;
+			pdev->pcie_flags_reg |= PCI_EXP_TYPE_DOWNSTREAM;
+		}
 	}
 }
 
@@ -2488,12 +2500,8 @@ static int only_one_child(struct pci_bus *bus)
 	 * A PCIe Downstream Port normally leads to a Link with only Device
 	 * 0 on it (PCIe spec r3.1, sec 7.3.1).  As an optimization, scan
 	 * only for Device 0 in that situation.
-	 *
-	 * Checking has_secondary_link is a hack to identify Downstream
-	 * Ports because sometimes Switches are configured such that the
-	 * PCIe Port Type labels are backwards.
 	 */
-	if (bridge && pci_is_pcie(bridge) && bridge->has_secondary_link)
+	if (bridge && pci_is_pcie(bridge) && pcie_downstream_port(bridge))
 		return 1;
 
 	return 0;

drivers/pci/vc.c

@@ -13,6 +13,8 @@
 #include <linux/pci_regs.h>
 #include <linux/types.h>
 
+#include "pci.h"
+
 /**
  * pci_vc_save_restore_dwords - Save or restore a series of dwords
  * @dev: device
@@ -105,7 +107,7 @@ static void pci_vc_enable(struct pci_dev *dev, int pos, int res)
 	struct pci_dev *link = NULL;
 
 	/* Enable VCs from the downstream device */
-	if (!dev->has_secondary_link)
+	if (!pci_is_pcie(dev) || !pcie_downstream_port(dev))
 		return;
 
 	ctrl_pos = pos + PCI_VC_RES_CTRL + (res * PCI_CAP_VC_PER_VC_SIZEOF);

include/linux/pci.h

@@ -418,7 +418,6 @@ struct pci_dev {
 	unsigned int	broken_intx_masking:1;	/* INTx masking can't be used */
 	unsigned int	io_window_1k:1;		/* Intel bridge 1K I/O windows */
 	unsigned int	irq_managed:1;
-	unsigned int	has_secondary_link:1;
 	unsigned int	non_compliant_bars:1;	/* Broken BARs; ignore them */
 	unsigned int	is_probed:1;		/* Device probing in progress */
 	unsigned int	link_active_reporting:1;/* Device capable of reporting link active */