@@ -17099,6 +17099,12 @@ F: include/linux/of_pci.h
F: include/linux/pci*
F: include/uapi/linux/pci*
+PCIE BANDWIDTH CONTROLLER
+M: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
+L: linux-pci@vger.kernel.org
+S: Supported
+F: drivers/pci/pcie/bwctrl.c
+
PCIE DRIVER FOR AMAZON ANNAPURNA LABS
M: Jonathan Chocron <jonnyc@amazon.com>
L: linux-pci@vger.kernel.org
@@ -133,5 +133,7 @@ void pciehp_unconfigure_device(struct controller *ctrl, bool presence)
pci_dev_put(dev);
}
+ pcie_reset_lbms_count(ctrl->pcie->port);
+
pci_unlock_rescan_remove();
}
@@ -608,6 +608,17 @@ static inline void pcie_set_ecrc_checking(struct pci_dev *dev) { }
static inline void pcie_ecrc_get_policy(char *str) { }
#endif
+#ifdef CONFIG_PCIE_BWCTRL
+void pcie_reset_lbms_count(struct pci_dev *port);
+int pcie_lbms_count(struct pci_dev *port, unsigned long *val);
+#else
+static inline void pcie_reset_lbms_count(struct pci_dev *port) { }
+static inline int pcie_lbms_count(struct pci_dev *port, unsigned long *val)
+{
+ return -EOPNOTSUPP;
+}
+#endif
+
struct pci_dev_reset_methods {
u16 vendor;
u16 device;
@@ -146,6 +146,18 @@ config PCIE_PTM
This is only useful if you have devices that support PTM, but it
is safe to enable even if you don't.
+config PCIE_BWCTRL
+ bool "PCI Express Bandwidth Controller"
+ depends on PCIEPORTBUS
+ help
+ This enables PCI Express Bandwidth Controller. The Bandwidth
+ Controller allows controlling PCIe Link Speed and listens for Link
+ Bandwidth Change Notifications. The current Link Speed is available
+ through /sys/bus/pci/devices/.../current_link_speed.
+
+ If you know Link Width or Speed changes occur (e.g., to correct
+ unreliable links), you may answer Y.
+
config PCIE_EDR
bool "PCI Express Error Disconnect Recover support"
depends on PCIE_DPC && ACPI
@@ -12,4 +12,5 @@ obj-$(CONFIG_PCIEAER_INJECT) += aer_inject.o
obj-$(CONFIG_PCIE_PME) += pme.o
obj-$(CONFIG_PCIE_DPC) += dpc.o
obj-$(CONFIG_PCIE_PTM) += ptm.o
+obj-$(CONFIG_PCIE_BWCTRL) += bwctrl.o
obj-$(CONFIG_PCIE_EDR) += edr.o
new file mode 100644
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * PCIe bandwidth controller
+ *
+ * Author: Alexandru Gagniuc <mr.nuke.me@gmail.com>
+ *
+ * Copyright (C) 2019 Dell Inc
+ * Copyright (C) 2023-2024 Intel Corporation
+ *
+ * This service port driver hooks into the Bandwidth Notification interrupt
+ * watching for changes or links becoming degraded in operation. It updates
+ * the cached Current Link Speed that is exposed to user space through sysfs.
+ */
+
+#define dev_fmt(fmt) "bwctrl: " fmt
+
+#include <linux/atomic.h>
+#include <linux/cleanup.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/pci.h>
+#include <linux/rwsem.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+#include "../pci.h"
+#include "portdrv.h"
+
+/**
+ * struct pcie_bwctrl_data - PCIe bandwidth controller
+ * @lbms_count: Count for LBMS (since last reset)
+ */
+struct pcie_bwctrl_data {
+ atomic_t lbms_count;
+};
+
+/* Prevents port removal during link speed changes and LBMS count accessors */
+static DECLARE_RWSEM(pcie_bwctrl_remove_rwsem);
+
+static void pcie_bwnotif_enable(struct pcie_device *srv)
+{
+ struct pcie_bwctrl_data *data = get_service_data(srv);
+ struct pci_dev *port = srv->port;
+ u16 link_status;
+ int ret;
+
+ /* Count LBMS seen so far as one */
+ ret = pcie_capability_read_word(port, PCI_EXP_LNKSTA, &link_status);
+ if (ret == PCIBIOS_SUCCESSFUL && link_status & PCI_EXP_LNKSTA_LBMS)
+ atomic_inc(&data->lbms_count);
+
+ pcie_capability_set_word(port, PCI_EXP_LNKCTL,
+ PCI_EXP_LNKCTL_LBMIE | PCI_EXP_LNKCTL_LABIE);
+ pcie_capability_write_word(port, PCI_EXP_LNKSTA,
+ PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_LABS);
+
+ /*
+ * Update after enabling notifications & clearing status bits ensures
+ * link speed is up to date.
+ */
+ pcie_update_link_speed(port->subordinate);
+}
+
+static void pcie_bwnotif_disable(struct pci_dev *port)
+{
+ pcie_capability_clear_word(port, PCI_EXP_LNKCTL,
+ PCI_EXP_LNKCTL_LBMIE | PCI_EXP_LNKCTL_LABIE);
+}
+
+static irqreturn_t pcie_bwnotif_irq_thread(int irq, void *context)
+{
+ struct pcie_device *srv = context;
+ struct pcie_bwctrl_data *data = get_service_data(srv);
+ struct pci_dev *port = srv->port;
+ u16 link_status, events;
+ int ret;
+
+ ret = pcie_capability_read_word(port, PCI_EXP_LNKSTA, &link_status);
+ events = link_status & (PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_LABS);
+
+ if (ret != PCIBIOS_SUCCESSFUL || !events)
+ return IRQ_NONE;
+
+ if (events & PCI_EXP_LNKSTA_LBMS)
+ atomic_inc(&data->lbms_count);
+
+ pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
+
+ /*
+ * Interrupts will not be triggered from any further Link Speed
+ * change until LBMS is cleared by the write. Therefore, re-read the
+ * speed (inside pcie_update_link_speed()) after LBMS has been
+ * cleared to avoid missing link speed changes.
+ */
+ pcie_update_link_speed(port->subordinate);
+
+ return IRQ_HANDLED;
+}
+
+void pcie_reset_lbms_count(struct pci_dev *port)
+{
+ struct pcie_bwctrl_data *data;
+
+ guard(rwsem_read)(&pcie_bwctrl_remove_rwsem);
+ data = port->link_bwctrl;
+ if (data)
+ atomic_set(&data->lbms_count, 0);
+}
+
+int pcie_lbms_count(struct pci_dev *port, unsigned long *val)
+{
+ struct pcie_bwctrl_data *data;
+
+ guard(rwsem_read)(&pcie_bwctrl_remove_rwsem);
+ data = port->link_bwctrl;
+ if (!data)
+ return -ENOTTY;
+
+ *val = atomic_read(&data->lbms_count);
+
+ return 0;
+}
+
+static int pcie_bwnotif_probe(struct pcie_device *srv)
+{
+ struct pci_dev *port = srv->port;
+ int ret;
+
+ struct pcie_bwctrl_data *data __free(kfree) =
+ kzalloc(sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ set_service_data(srv, data);
+
+ ret = request_threaded_irq(srv->irq, NULL, pcie_bwnotif_irq_thread,
+ IRQF_SHARED | IRQF_ONESHOT, "PCIe bwctrl", srv);
+ if (ret)
+ return ret;
+
+ port->link_bwctrl = no_free_ptr(data);
+ pcie_bwnotif_enable(srv);
+ pci_info(port, "enabled with IRQ %d\n", srv->irq);
+
+ return 0;
+}
+
+static void pcie_bwnotif_remove(struct pcie_device *srv)
+{
+ struct pcie_bwctrl_data *data = get_service_data(srv);
+
+ scoped_guard(rwsem_write, &pcie_bwctrl_remove_rwsem)
+ srv->port->link_bwctrl = NULL;
+
+ pcie_bwnotif_disable(srv->port);
+ free_irq(srv->irq, srv);
+ kfree(data);
+}
+
+static int pcie_bwnotif_suspend(struct pcie_device *srv)
+{
+ pcie_bwnotif_disable(srv->port);
+ return 0;
+}
+
+static int pcie_bwnotif_resume(struct pcie_device *srv)
+{
+ pcie_bwnotif_enable(srv);
+ return 0;
+}
+
+static struct pcie_port_service_driver pcie_bwctrl_driver = {
+ .name = "pcie_bwctrl",
+ .port_type = PCIE_ANY_PORT,
+ .service = PCIE_PORT_SERVICE_BWCTRL,
+ .probe = pcie_bwnotif_probe,
+ .suspend = pcie_bwnotif_suspend,
+ .resume = pcie_bwnotif_resume,
+ .remove = pcie_bwnotif_remove,
+};
+
+int __init pcie_bwctrl_init(void)
+{
+ return pcie_port_service_register(&pcie_bwctrl_driver);
+}
@@ -68,7 +68,7 @@ static int pcie_message_numbers(struct pci_dev *dev, int mask,
*/
if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP |
- PCIE_PORT_SERVICE_BWNOTIF)) {
+ PCIE_PORT_SERVICE_BWCTRL)) {
pcie_capability_read_word(dev, PCI_EXP_FLAGS, ®16);
*pme = FIELD_GET(PCI_EXP_FLAGS_IRQ, reg16);
nvec = *pme + 1;
@@ -150,11 +150,11 @@ static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
/* PME, hotplug and bandwidth notification share an MSI/MSI-X vector */
if (mask & (PCIE_PORT_SERVICE_PME | PCIE_PORT_SERVICE_HP |
- PCIE_PORT_SERVICE_BWNOTIF)) {
+ PCIE_PORT_SERVICE_BWCTRL)) {
pcie_irq = pci_irq_vector(dev, pme);
irqs[PCIE_PORT_SERVICE_PME_SHIFT] = pcie_irq;
irqs[PCIE_PORT_SERVICE_HP_SHIFT] = pcie_irq;
- irqs[PCIE_PORT_SERVICE_BWNOTIF_SHIFT] = pcie_irq;
+ irqs[PCIE_PORT_SERVICE_BWCTRL_SHIFT] = pcie_irq;
}
if (mask & PCIE_PORT_SERVICE_AER)
@@ -271,7 +271,7 @@ static int get_port_device_capability(struct pci_dev *dev)
pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &linkcap);
if (linkcap & PCI_EXP_LNKCAP_LBNC)
- services |= PCIE_PORT_SERVICE_BWNOTIF;
+ services |= PCIE_PORT_SERVICE_BWCTRL;
}
return services;
@@ -829,6 +829,7 @@ static void __init pcie_init_services(void)
pcie_pme_init();
pcie_dpc_init();
pcie_hp_init();
+ pcie_bwctrl_init();
}
static int __init pcie_portdrv_init(void)
@@ -20,8 +20,8 @@
#define PCIE_PORT_SERVICE_HP (1 << PCIE_PORT_SERVICE_HP_SHIFT)
#define PCIE_PORT_SERVICE_DPC_SHIFT 3 /* Downstream Port Containment */
#define PCIE_PORT_SERVICE_DPC (1 << PCIE_PORT_SERVICE_DPC_SHIFT)
-#define PCIE_PORT_SERVICE_BWNOTIF_SHIFT 4 /* Bandwidth notification */
-#define PCIE_PORT_SERVICE_BWNOTIF (1 << PCIE_PORT_SERVICE_BWNOTIF_SHIFT)
+#define PCIE_PORT_SERVICE_BWCTRL_SHIFT 4 /* Bandwidth Controller (notifications) */
+#define PCIE_PORT_SERVICE_BWCTRL (1 << PCIE_PORT_SERVICE_BWCTRL_SHIFT)
#define PCIE_PORT_DEVICE_MAXSERVICES 5
@@ -51,6 +51,12 @@ int pcie_dpc_init(void);
static inline int pcie_dpc_init(void) { return 0; }
#endif
+#ifdef CONFIG_PCIE_BWCTRL
+int pcie_bwctrl_init(void);
+#else
+static inline int pcie_bwctrl_init(void) { return 0; }
+#endif
+
/* Port Type */
#define PCIE_ANY_PORT (~0)
@@ -35,7 +35,12 @@
static bool pcie_lbms_seen(struct pci_dev *dev, u16 lnksta)
{
- return lnksta & PCI_EXP_LNKSTA_LBMS;
+ unsigned long count;
+
+ if (pcie_lbms_count(dev, &count) < 0)
+ return lnksta & PCI_EXP_LNKSTA_LBMS;
+
+ return count > 0;
}
/*
@@ -314,6 +314,7 @@ struct pci_vpd {
};
struct irq_affinity;
+struct pcie_bwctrl_data;
struct pcie_link_state;
struct pci_sriov;
struct pci_p2pdma;
@@ -494,6 +495,9 @@ struct pci_dev {
unsigned int dpc_rp_extensions:1;
u8 dpc_rp_log_size;
#endif
+#ifdef CONFIG_PCIE_BWCTRL
+ struct pcie_bwctrl_data *link_bwctrl;
+#endif
#ifdef CONFIG_PCI_ATS
union {
struct pci_sriov *sriov; /* PF: SR-IOV info */
This mostly reverts the commit b4c7d2076b4e ("PCI/LINK: Remove bandwidth notification"). An upcoming commit extends this driver building PCIe bandwidth controller on top of it. The PCIe bandwidth notification were first added in the commit e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth notification") but later had to be removed. The significant changes compared with the old bandwidth notification driver include: 1) Don't print the notifications into kernel log, just keep the Link Speed cached into the struct pci_bus updated. While somewhat unfortunate, the log spam was the source of complaints that eventually lead to the removal of the bandwidth notifications driver (see the links below for further information). 2) Besides the Link Bandwidth Management Interrupt, enable also Link Autonomous Bandwidth Interrupt to cover the other source of bandwidth changes. 3) Use threaded IRQ with IRQF_ONESHOT to handle Bandwidth Notification Interrupts to address the problem fixed in the commit 3e82a7f9031f ("PCI/LINK: Supply IRQ handler so level-triggered IRQs are acked")). 4) Handle Link Speed updates robustly. Refresh the cached Link Speed when enabling Bandwidth Notification Interrupts, and solve the race between Link Speed read and LBMS/LABS update in pcie_bwnotif_irq_thread(). 5) Use concurrency safe LNKCTL RMW operations. 6) The driver is now called PCIe bwctrl (bandwidth controller) instead of just bandwidth notifications because of increased scope and functionality within the driver. 7) Coexist with the Target Link Speed quirk in pcie_failed_link_retrain(). Provide LBMS counting API for it. 8) Tweaks to variable/functions names for consistency and length reasons. Bandwidth Notifications enable the cur_bus_speed in the struct pci_bus to keep track PCIe Link Speed changes. Link: https://lore.kernel.org/all/20190429185611.121751-1-helgaas@kernel.org/ Link: https://lore.kernel.org/linux-pci/20190501142942.26972-1-keith.busch@intel.com/ Link: https://lore.kernel.org/linux-pci/20200115221008.GA191037@google.com/ Suggested-by: Lukas Wunner <lukas@wunner.de> # Building bwctrl on top of bwnotif Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> --- MAINTAINERS | 6 + drivers/pci/hotplug/pciehp_pci.c | 2 + drivers/pci/pci.h | 11 ++ drivers/pci/pcie/Kconfig | 12 ++ drivers/pci/pcie/Makefile | 1 + drivers/pci/pcie/bwctrl.c | 185 +++++++++++++++++++++++++++++++ drivers/pci/pcie/portdrv.c | 9 +- drivers/pci/pcie/portdrv.h | 10 +- drivers/pci/quirks.c | 7 +- include/linux/pci.h | 4 + 10 files changed, 240 insertions(+), 7 deletions(-) create mode 100644 drivers/pci/pcie/bwctrl.c