[PATCH v17 2/4] PCI: Add support for drivers to register optin or veto of D3

[Mario Limonciello <mario.limonciello@amd.com>]

commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
changed pci_bridge_d3_possible() so that any vendor's PCIe ports
from modern machines (>=2015) are allowed to be put into D3.

This policy change has worked for most machines, but the behavior
is improved with `pcie_port_pm=off` on some others.

Add support for drivers to register both 'optin' and 'veto' callbacks
and a priority which can be used for deciding whether a device should
use D3. When drivers register the callbacks, the list is sorted by
priority.

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/pci/pci.c   | 143 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pci.h |   9 +++
 2 files changed, 152 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 59c01d68c6d5..06ab73f58adf 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -21,6 +21,7 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
+#include <linux/list_sort.h>
 #include <linux/log2.h>
 #include <linux/logic_pio.h>
 #include <linux/pm_wakeup.h>
@@ -54,6 +55,8 @@ unsigned int pci_pm_d3hot_delay;
 static void pci_pme_list_scan(struct work_struct *work);
 
 static LIST_HEAD(pci_pme_list);
+static LIST_HEAD(d3_possible_list);
+static DEFINE_MUTEX(d3_possible_list_mutex);
 static DEFINE_MUTEX(pci_pme_list_mutex);
 static DECLARE_DELAYED_WORK(pci_pme_work, pci_pme_list_scan);
 
@@ -161,6 +164,14 @@ static bool pcie_ats_disabled;
 /* If set, the PCI config space of each device is printed during boot. */
 bool pci_early_dump;
 
+/* Preferences set by a driver for D3 optin/veto */
+enum driver_d3_pref {
+	D3_PREF_UNSET,	/* Not configured by driver */
+	D3_PREF_NONE,	/* Driver does not care */
+	D3_PREF_OPTIN,	/* Driver prefers D3 */
+	D3_PREF_VETO,	/* Driver vetoes D3 */
+};
+
 bool pci_ats_disabled(void)
 {
 	return pcie_ats_disabled;
@@ -3031,6 +3042,10 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
 		if (pci_bridge_d3_force)
 			return true;
 
+		/* check for any driver optin of D3 for the bridge */
+		if (bridge->driver_d3 == D3_PREF_OPTIN)
+			return true;
+
 		/* Even the oldest 2010 Thunderbolt controller supports D3. */
 		if (bridge->is_thunderbolt)
 			return true;
@@ -3050,6 +3065,10 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
 		if (dmi_check_system(bridge_d3_blacklist))
 			return false;
 
+		/* check for any driver veto for D3 for the bridge */
+		if (bridge->driver_d3 == D3_PREF_VETO)
+			return false;
+
 		/*
 		 * It should be safe to put PCIe ports from 2015 or newer
 		 * to D3.
@@ -3168,6 +3187,130 @@ void pci_d3cold_disable(struct pci_dev *dev)
 }
 EXPORT_SYMBOL_GPL(pci_d3cold_disable);
 
+static struct pci_dev *pci_get_upstream_port(struct pci_dev *pci_dev)
+{
+	struct pci_dev *bridge;
+
+	bridge = pci_upstream_bridge(pci_dev);
+	if (!bridge)
+		return NULL;
+
+	if (!pci_is_pcie(bridge))
+		return NULL;
+
+	switch (pci_pcie_type(bridge)) {
+	case PCI_EXP_TYPE_ROOT_PORT:
+	case PCI_EXP_TYPE_UPSTREAM:
+	case PCI_EXP_TYPE_DOWNSTREAM:
+		return bridge;
+	default:
+		break;
+	};
+
+	return NULL;
+}
+
+static void pci_refresh_d3_possible(void)
+{
+	struct pci_d3_driver_ops *driver;
+	struct pci_dev *pci_dev = NULL;
+	struct pci_dev *bridge;
+
+	/* 1st pass: unset any preferences set a previous invocation */
+	while ((pci_dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pci_dev))) {
+		bridge = pci_get_upstream_port(pci_dev);
+		if (!bridge)
+			continue;
+
+		if (bridge->driver_d3 != D3_PREF_UNSET)
+			bridge->driver_d3 = D3_PREF_UNSET;
+	}
+
+	pci_dev = NULL;
+
+	/* 2nd pass: update the preference and refresh bridge_d3 */
+	while ((pci_dev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pci_dev))) {
+		bridge = pci_get_upstream_port(pci_dev);
+		if (!bridge)
+			continue;
+
+		/* don't make multiple passes on the same device */
+		if (bridge->driver_d3 != D3_PREF_UNSET)
+			continue;
+
+		/* the list is pre-sorted by highest priority */
+		mutex_lock(&d3_possible_list_mutex);
+		list_for_each_entry(driver, &d3_possible_list, list_node) {
+			/* another higher priority driver already set preference */
+			if (bridge->driver_d3 != D3_PREF_UNSET)
+				break;
+			/* check for opt in to D3 */
+			if (driver->optin && driver->optin(bridge))
+				bridge->driver_d3 = D3_PREF_OPTIN;
+			/* check for opt out of D3 */
+			else if (driver->veto && driver->veto(bridge))
+				bridge->driver_d3 = D3_PREF_VETO;
+		}
+		mutex_unlock(&d3_possible_list_mutex);
+
+		/* no driver set a preference */
+		if (bridge->driver_d3 == D3_PREF_UNSET)
+			bridge->driver_d3 = D3_PREF_NONE;
+
+		/* update bridge_d3 */
+		pci_bridge_d3_update(pci_dev);
+	}
+}
+
+static int pci_d3_driver_cmp(void *priv, const struct list_head *_a,
+			   const struct list_head *_b)
+{
+	struct pci_d3_driver_ops *a = container_of(_a, typeof(*a), list_node);
+	struct pci_d3_driver_ops *b = container_of(_b, typeof(*b), list_node);
+
+	if (a->priority < b->priority)
+		return -1;
+	else if (a->priority > b->priority)
+		return 1;
+	return 0;
+}
+
+/**
+ * pci_register_d3_possible_cb - Register a driver callback for checking d3 veto
+ * @arg: driver provided structure with function pointer and priority
+ *
+ * This function can be used by drivers to register a callback that can be
+ * used to veto a device going into D3.
+ * Returns 0 on success, error code on failure.
+ */
+int pci_register_d3_possible_cb(struct pci_d3_driver_ops *arg)
+{
+	mutex_lock(&d3_possible_list_mutex);
+	list_add(&arg->list_node, &d3_possible_list);
+	list_sort(NULL, &d3_possible_list, pci_d3_driver_cmp);
+	mutex_unlock(&d3_possible_list_mutex);
+	pci_refresh_d3_possible();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_register_d3_possible_cb);
+
+/**
+ * pci_unregister_d3_possible_cb - Unregister a driver callback for checking d3 veto
+ * @arg: driver provided structure with function pointer and priority
+ *
+ * This function can be used by drivers to unregister a callback that can be
+ * used to veto a device going into D3.
+ */
+void pci_unregister_d3_possible_cb(struct pci_d3_driver_ops *arg)
+{
+	mutex_lock(&d3_possible_list_mutex);
+	list_del(&arg->list_node);
+	list_sort(NULL, &d3_possible_list, pci_d3_driver_cmp);
+	mutex_unlock(&d3_possible_list_mutex);
+	pci_refresh_d3_possible();
+}
+EXPORT_SYMBOL_GPL(pci_unregister_d3_possible_cb);
+
 /**
  * pci_pm_init - Initialize PM functions of given PCI device
  * @dev: PCI device to handle.
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 8c7c2c3c6c65..863399e78869 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -389,6 +389,7 @@ struct pci_dev {
 						   bit manually */
 	unsigned int	d3hot_delay;	/* D3hot->D0 transition time in ms */
 	unsigned int	d3cold_delay;	/* D3cold->D0 transition time in ms */
+	unsigned int	driver_d3;	/* Driver D3 request preference */
 
 #ifdef CONFIG_PCIEASPM
 	struct pcie_link_state	*link_state;	/* ASPM link state */
@@ -1404,6 +1405,14 @@ void pci_d3cold_disable(struct pci_dev *dev);
 bool pcie_relaxed_ordering_enabled(struct pci_dev *dev);
 void pci_resume_bus(struct pci_bus *bus);
 void pci_bus_set_current_state(struct pci_bus *bus, pci_power_t state);
+struct pci_d3_driver_ops {
+	struct list_head list_node;
+	int priority;
+	bool (*optin)(struct pci_dev *pdev);
+	bool (*veto)(struct pci_dev *pdev);
+};
+int pci_register_d3_possible_cb(struct pci_d3_driver_ops *arg);
+void pci_unregister_d3_possible_cb(struct pci_d3_driver_ops *arg);
 
 /* For use by arch with custom probe code */
 void set_pcie_port_type(struct pci_dev *pdev);
-- 
2.34.1