PCI: Add Downstream Port Containment driver

Add driver for the PCI Express Downstream Port Containment extended
capability.  DPC is an optional capability to contain uncorrectable errors
below a port.

For more information on DPC, please see PCI Express Base Specification
Revision 4, section 7.31, or view the PCI-SIG DPC ECN here:

  https://pcisig.com/sites/default/files/specification_documents/ECN_DPC_2012-02-09_finalized.pdf

When a DPC event is triggered, the hardware disables downstream links, so
the DPC driver schedules removal for all devices below this port.  This may
happen concurrently with a PCIe hotplug driver if enabled.  When all
downstream devices are removed and the link state transitions to disabled,
the DPC driver clears the DPC status and interrupt bits so the link may
retrain for a newly connected device.

[bhelgaas: clear (not set) DPC_CTL bits on remove, whitespace cleanup]
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Lukas Wunner <lukas@wunner.de>

3 files changed, 179 insertions, 0 deletions

diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
index 72db7f4..22ca641 100644
--- a/drivers/pci/pcie/Kconfig
+++ b/drivers/pci/pcie/Kconfig
@@ -81,3 +81,17 @@ endchoice
 config PCIE_PME
 	def_bool y
 	depends on PCIEPORTBUS && PM
+
+config PCIE_DPC
+	tristate "PCIe Downstream Port Containment support"
+	depends on PCIEPORTBUS
+	default n
+	help
+	  This enables PCI Express Downstream Port Containment (DPC)
+	  driver support.  DPC events from Root and Downstream ports
+	  will be handled by the DPC driver.  If your system doesn't
+	  have this capability or you do not want to use this feature,
+	  it is safe to answer N.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pcie-dpc.
diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
index 00c62df..b24525b 100644
--- a/drivers/pci/pcie/Makefile
+++ b/drivers/pci/pcie/Makefile
@@ -14,3 +14,5 @@ obj-$(CONFIG_PCIEPORTBUS)	+= pcieportdrv.o
 obj-$(CONFIG_PCIEAER)		+= aer/
 
 obj-$(CONFIG_PCIE_PME) += pme.o
+
+obj-$(CONFIG_PCIE_DPC) += pcie-dpc.o
diff --git a/drivers/pci/pcie/pcie-dpc.c b/drivers/pci/pcie/pcie-dpc.c
new file mode 100644
index 0000000..ab552f1
--- /dev/null
+++ b/drivers/pci/pcie/pcie-dpc.c
@@ -0,0 +1,163 @@
+/*
+ * PCI Express Downstream Port Containment services driver
+ * Copyright (C) 2016 Intel Corp.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/pcieport_if.h>
+
+struct dpc_dev {
+	struct pcie_device	*dev;
+	struct work_struct 	work;
+	int 			cap_pos;
+};
+
+static void dpc_wait_link_inactive(struct pci_dev *pdev)
+{
+	unsigned long timeout = jiffies + HZ;
+	u16 lnk_status;
+
+	pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
+	while (lnk_status & PCI_EXP_LNKSTA_DLLLA &&
+					!time_after(jiffies, timeout)) {
+		msleep(10);
+		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
+	}
+	if (lnk_status & PCI_EXP_LNKSTA_DLLLA)
+		dev_warn(&pdev->dev, "Link state not disabled for DPC event");
+}
+
+static void interrupt_event_handler(struct work_struct *work)
+{
+	struct dpc_dev *dpc = container_of(work, struct dpc_dev, work);
+	struct pci_dev *dev, *temp, *pdev = dpc->dev->port;
+	struct pci_bus *parent = pdev->subordinate;
+
+	pci_lock_rescan_remove();
+	list_for_each_entry_safe_reverse(dev, temp, &parent->devices,
+					 bus_list) {
+		pci_dev_get(dev);
+		pci_stop_and_remove_bus_device(dev);
+		pci_dev_put(dev);
+	}
+	pci_unlock_rescan_remove();
+
+	dpc_wait_link_inactive(pdev);
+	pci_write_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_STATUS,
+		PCI_EXP_DPC_STATUS_TRIGGER | PCI_EXP_DPC_STATUS_INTERRUPT);
+}
+
+static irqreturn_t dpc_irq(int irq, void *context)
+{
+	struct dpc_dev *dpc = (struct dpc_dev *)context;
+	struct pci_dev *pdev = dpc->dev->port;
+	u16 status, source;
+
+	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_STATUS, &status);
+	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_SOURCE_ID,
+			     &source);
+	if (!status)
+		return IRQ_NONE;
+
+	dev_info(&dpc->dev->device, "DPC containment event, status:%#06x source:%#06x\n",
+		status, source);
+
+	if (status & PCI_EXP_DPC_STATUS_TRIGGER) {
+		u16 reason = (status >> 1) & 0x3;
+
+		dev_warn(&dpc->dev->device, "DPC %s triggered, remove downstream devices\n",
+			 (reason == 0) ? "unmasked uncorrectable error" :
+			 (reason == 1) ? "ERR_NONFATAL" :
+			 (reason == 2) ? "ERR_FATAL" : "extended error");
+		schedule_work(&dpc->work);
+	}
+	return IRQ_HANDLED;
+}
+
+#define FLAG(x, y) (((x) & (y)) ? '+' : '-')
+static int dpc_probe(struct pcie_device *dev)
+{
+	struct dpc_dev *dpc;
+	struct pci_dev *pdev = dev->port;
+	int status;
+	u16 ctl, cap;
+
+	dpc = kzalloc(sizeof(*dpc), GFP_KERNEL);
+	if (!dpc)
+		return -ENOMEM;
+
+	dpc->cap_pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DPC);
+	dpc->dev = dev;
+	INIT_WORK(&dpc->work, interrupt_event_handler);
+	set_service_data(dev, dpc);
+
+	status = request_irq(dev->irq, dpc_irq, IRQF_SHARED, "pcie-dpc", dpc);
+	if (status) {
+		dev_warn(&dev->device, "request IRQ%d failed: %d\n", dev->irq,
+			 status);
+		goto out;
+	}
+
+	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CAP, &cap);
+	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, &ctl);
+
+	ctl |= PCI_EXP_DPC_CTL_EN_NONFATAL | PCI_EXP_DPC_CTL_INT_EN;
+	pci_write_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, ctl);
+
+	dev_info(&dev->device, "DPC error containment capabilities: Int Msg #%d, RPExt%c PoisonedTLP%c SwTrigger%c RP PIO Log %d, DL_ActiveErr%c\n",
+		cap & 0xf, FLAG(cap, PCI_EXP_DPC_CAP_RP_EXT),
+		FLAG(cap, PCI_EXP_DPC_CAP_POISONED_TLP),
+		FLAG(cap, PCI_EXP_DPC_CAP_SW_TRIGGER), (cap >> 8) & 0xf,
+		FLAG(cap, PCI_EXP_DPC_CAP_DL_ACTIVE));
+	return status;
+ out:
+	kfree(dpc);
+	return status;
+}
+
+static void dpc_remove(struct pcie_device *dev)
+{
+	struct dpc_dev *dpc = get_service_data(dev);
+	struct pci_dev *pdev = dev->port;
+	u16 ctl;
+
+	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, &ctl);
+	ctl &= ~(PCI_EXP_DPC_CTL_EN_NONFATAL | PCI_EXP_DPC_CTL_INT_EN);
+	pci_write_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, ctl);
+
+	free_irq(dev->irq, dpc);
+	kfree(dpc);
+}
+
+static struct pcie_port_service_driver dpcdriver = {
+	.name		= "dpc",
+	.port_type	= PCI_EXP_TYPE_ROOT_PORT | PCI_EXP_TYPE_DOWNSTREAM,
+	.service	= PCIE_PORT_SERVICE_DPC,
+	.probe		= dpc_probe,
+	.remove		= dpc_remove,
+};
+
+static int __init dpc_service_init(void)
+{
+	return pcie_port_service_register(&dpcdriver);
+}
+
+static void __exit dpc_service_exit(void)
+{
+	pcie_port_service_unregister(&dpcdriver);
+}
+
+MODULE_DESCRIPTION("PCI Express Downstream Port Containment driver");
+MODULE_AUTHOR("Keith Busch <keith.busch@intel.com>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("0.1");
+
+module_init(dpc_service_init);
+module_exit(dpc_service_exit);