PCI: Make link active reporting detection generic

task #29600094

commit f0157160b359b1d263ee9d4e0a435a7ad85bbcea upstream.
Backport summary: for 4.19 kernel ICX PCIe Gen4 support.

The spec has timing requirements when waiting for a link to become active
after a conventional reset.  Implement those hard delays when waiting for
an active link so pciehp and dpc drivers don't need to duplicate this.

For devices that don't support data link layer active reporting, wait the
fixed time recommended by the PCIe spec.
Signed-off-by: NKeith Busch <keith.busch@intel.com>
[bhelgaas: changelog]
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NSinan Kaya <okaya@kernel.org>
(cherry picked from commit f0157160b359b1d263ee9d4e0a435a7ad85bbcea)
Signed-off-by: NEthan Zhao <haifeng.zhao@intel.com>
Signed-off-by: NArtie Ding <artie.ding@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

drivers/pci/hotplug/pciehp.h

@@ -96,11 +96,6 @@ struct slot {
  *	interrupt (PCIe r4.0, sec 6.7.3.2)
  * @cmd_busy: flag set on Slot Control register write, cleared by IRQ handler
  *	on reception of a Command Completed event
- * @link_active_reporting: cached copy of Data Link Layer Link Active Reporting
- *	Capable bit in Link Capabilities register; if this bit is zero, the
- *	Data Link Layer Link Active bit in the Link Status register will never
- *	be set and the driver is thus confined to wait 1 second before assuming
- *	the link to a hotplugged device is up and accessing it
  * @notification_enabled: whether the IRQ was requested successfully
  * @power_fault_detected: whether a power fault was detected by the hardware
  *	that has not yet been cleared by the user
@@ -122,7 +117,6 @@ struct controller {
 	struct task_struct *poll_thread;
 	unsigned long cmd_started;	/* jiffies */
 	unsigned int cmd_busy:1;
-	unsigned int link_active_reporting:1;
 	unsigned int notification_enabled:1;
 	unsigned int power_fault_detected;
 	atomic_t pending_events;

drivers/pci/hotplug/pciehp_hpc.c

@@ -217,13 +217,6 @@ bool pciehp_check_link_active(struct controller *ctrl)
 	return ret;
 }
 
-static void pcie_wait_link_active(struct controller *ctrl)
-{
-	struct pci_dev *pdev = ctrl_dev(ctrl);
-
-	pcie_wait_for_link(pdev, true);
-}
-
 static bool pci_bus_check_dev(struct pci_bus *bus, int devfn)
 {
 	u32 l;
@@ -256,18 +249,9 @@ int pciehp_check_link_status(struct controller *ctrl)
 	bool found;
 	u16 lnk_status;
 
-	/*
-	 * Data Link Layer Link Active Reporting must be capable for
-	 * hot-plug capable downstream port. But old controller might
-	 * not implement it. In this case, we wait for 1000 ms.
-	*/
-	if (ctrl->link_active_reporting)
-		pcie_wait_link_active(ctrl);
-	else
-		msleep(1000);
+	if (!pcie_wait_for_link(pdev, true))
+		return -1;
 
-	/* wait 100ms before read pci conf, and try in 1s */
-	msleep(100);
 	found = pci_bus_check_dev(ctrl->pcie->port->subordinate,
 					PCI_DEVFN(0, 0));
 
@@ -888,8 +872,6 @@ struct controller *pcie_init(struct pcie_device *dev)
 
 	/* Check if Data Link Layer Link Active Reporting is implemented */
 	pcie_capability_read_dword(pdev, PCI_EXP_LNKCAP, &link_cap);
-	if (link_cap & PCI_EXP_LNKCAP_DLLLARC)
-		ctrl->link_active_reporting = 1;
 
 	/* Clear all remaining event bits in Slot Status register. */
 	pcie_capability_write_word(pdev, PCI_EXP_SLTSTA,

drivers/pci/pci.c

@@ -4538,21 +4538,42 @@ bool pcie_wait_for_link(struct pci_dev *pdev, bool active)
 	bool ret;
 	u16 lnk_status;
 
+	/*
+	 * Some controllers might not implement link active reporting. In this
+	 * case, we wait for 1000 + 100 ms.
+	 */
+	if (!pdev->link_active_reporting) {
+		msleep(1100);
+		return true;
+	}
+
+	/*
+	 * PCIe r4.0 sec 6.6.1, a component must enter LTSSM Detect within 20ms,
+	 * after which we should expect an link active if the reset was
+	 * successful. If so, software must wait a minimum 100ms before sending
+	 * configuration requests to devices downstream this port.
+	 *
+	 * If the link fails to activate, either the device was physically
+	 * removed or the link is permanently failed.
+	 */
+	if (active)
+		msleep(20);
 	for (;;) {
 		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
 		ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
 		if (ret == active)
-			return true;
+			break;
 		if (timeout <= 0)
 			break;
 		msleep(10);
 		timeout -= 10;
 	}
-
-	pci_info(pdev, "Data Link Layer Link Active not %s in 1000 msec\n",
-		 active ? "set" : "cleared");
-
-	return false;
+	if (active && ret)
+		msleep(100);
+	else if (ret != active)
+		pci_info(pdev, "Data Link Layer Link Active not %s in 1000 msec\n",
+			active ? "set" : "cleared");
+	return ret == active;
 }
 
 void pci_reset_secondary_bus(struct pci_dev *dev)

drivers/pci/pcie/dpc.c

@@ -140,10 +140,12 @@ static pci_ers_result_t dpc_reset_link(struct pci_dev *pdev)
 	pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS,
 			      PCI_EXP_DPC_STATUS_TRIGGER);
 
+	if (!pcie_wait_for_link(pdev, true))
+		return PCI_ERS_RESULT_DISCONNECT;
+
 	return PCI_ERS_RESULT_RECOVERED;
 }
 
-
 static void dpc_process_rp_pio_error(struct dpc_dev *dpc)
 {
 	struct device *dev = &dpc->dev->device;

drivers/pci/probe.c

@@ -718,6 +718,7 @@ static void pci_set_bus_speed(struct pci_bus *bus)
 
 		pcie_capability_read_dword(bridge, PCI_EXP_LNKCAP, &linkcap);
 		bus->max_bus_speed = pcie_link_speed[linkcap & PCI_EXP_LNKCAP_SLS];
+		bridge->link_active_reporting = !!(linkcap & PCI_EXP_LNKCAP_DLLLARC);
 
 		pcie_capability_read_word(bridge, PCI_EXP_LNKSTA, &linksta);
 		pcie_update_link_speed(bus, linksta);

include/linux/pci.h

@@ -405,6 +405,7 @@ struct pci_dev {
 	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 */
 	pci_dev_flags_t dev_flags;
 	atomic_t	enable_cnt;	/* pci_enable_device has been called */