bbswitch_dev: disable runtime PM on removal

Call pm_runtime_forbid() to balance it with pm_runtime_allow(), this
ensures that the runtime usage counter before loading and after
unloading match.

README.md

@@ -165,3 +165,9 @@ issues on this module in the issue tracker and provide the following details:
 
 Upload the generated tarball on the above Launchpad URL and provide a link to
 the comment containing your report.
+
+TODO
+----
+With the new PCI device approach, if load_state=0, then starting bumblebeed will
+unload bbswitch. Fix Bumblebee not to unload the module when the PM method is
+bbswitch and the loaded module is bbswitch.

bbswitch.c

@@ -8,6 +8,16 @@
  * # echo ON > /proc/acpi/bbswitch
  * Get status
  * # cat /proc/acpi/bbswitch
+ *
+ * Note: only one PCI driver (bbswitch, nouveau, etc.) can bind to a PCI device.
+ * When turning a device OFF, bbswitch tries to bind itself to the PCI device.
+ * When turning a device ON, bbswitch unbinds a device (if it was bound) before
+ * returning from the write.
+ *
+ * TODO is this true?
+ * The new dual module approach is used to allow for backwards compatibility,
+ * Bumblebee unloads any driver that is loaded for a device, that would however
+ * result in unloading the main bbswitch module.
  */
 /*
  *  Copyright (C) 2011-2013 Bumblebee Project
@@ -197,6 +207,26 @@ static int bbswitch_optimus_dsm(void) {
     return 0;
 }
 
+// Windows 8/8.1/10 do not use DSM to put the device in D3cold state,
+// instead it disables power resources on the parent PCIe port device.
+static bool has_pr3_support(void) {
+    acpi_handle parent_handle;
+    struct acpi_device *ad = NULL;
+
+    if (ACPI_FAILURE(acpi_get_parent(dis_handle, &parent_handle))) {
+        pr_warn("Failed to obtain the parent device\n");
+        return false;
+    }
+
+    acpi_bus_get_device(parent_handle, &ad);
+    if (!ad) {
+        pr_warn("Failed to obtain an ACPI device for handle\n");
+        return false;
+    }
+
+    return ad->power.flags.power_resources;
+}
+
 static int bbswitch_acpi_off(void) {
     if (dsm_type == DSM_TYPE_NVIDIA) {
         char args[] = {2, 0, 0, 0};
@@ -436,7 +466,9 @@ static int __init bbswitch_init(void) {
         return -ENODEV;
     }
 
-    if (!skip_optimus_dsm &&
+    if (has_pr3_support()) {
+        pr_info("skipping _DSM as _PR3 support is detected\n");
+    } else if (!skip_optimus_dsm &&
             has_dsm_func(acpi_optimus_dsm_muid, 0x100, 0x1A)) {
         dsm_type = DSM_TYPE_OPTIMUS;
         pr_info("detected an Optimus _DSM function\n");

bbswitch_dev.c

@@ -0,0 +1,100 @@
+/*
+ * TODO merge into main bbswitch module.
+ * TODO on ON call device_release_driver
+ * TODO how to bind to a specific device from kernel space? Can't use
+ *      driver_probe_device (https://lkml.org/lkml/2014/2/14/628). Maybe use
+ *      driver_override or new_id/bind/remove_id from userspace?
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/pci.h>
+#include <linux/module.h>
+#include <linux/pm_runtime.h>
+#include <linux/delay.h>
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Toggle the discrete graphics card (PCI driver)");
+MODULE_AUTHOR("Peter Wu <peter@lekensteyn.nl>");
+
+static int bbswitch_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
+{
+    /* TODO how to discover devices? */
+    /* Prevent kernel from detaching the PCI device for some devices that
+     * generate hotplug events. The graphics card is typically not physically
+     * removable. */
+    pci_ignore_hotplug(dev);
+
+    pm_runtime_set_active(&dev->dev); /* clear any errors */
+    /* Use autosuspend to avoid lspci waking up the device multiple times. */
+    pm_runtime_set_autosuspend_delay(&dev->dev, 2000);
+    pm_runtime_use_autosuspend(&dev->dev);
+    pm_runtime_allow(&dev->dev);
+    pm_runtime_put_autosuspend(&dev->dev);
+    return 0;
+}
+
+static void bbswitch_pci_remove(struct pci_dev *dev)
+{
+    pm_runtime_get_noresume(&dev->dev);
+    pm_runtime_dont_use_autosuspend(&dev->dev);
+    pm_runtime_forbid(&dev->dev);
+}
+
+static int bbswitch_runtime_suspend(struct device *dev) {
+    struct pci_dev *pdev = to_pci_dev(dev);
+
+    pr_info("disabling discrete graphics\n");
+
+    /* TODO if _PR3 is not supported, call Optimus DSM here. */
+    /* TODO for v1 Optimus, call DSM here. */
+
+    /* Save state now that the device is still awake, makes PCI layer happy */
+    pci_save_state(pdev);
+    /* TODO if _PR3 is supported, should this be PCI_D3hot? */
+    pci_set_power_state(pdev, PCI_D3cold);
+    return 0;
+}
+
+static int bbswitch_runtime_resume(struct device *dev) {
+    pr_info("enabling discrete graphics\n");
+
+    /* TODO for v1 Optimus, call DSM here. */
+    /* Nothing to do for Optimus, the PCI layer already moved into D0 state. */
+    return 0;
+}
+
+static struct dev_pm_ops bbswitch_pm_ops = {
+    .runtime_suspend = bbswitch_runtime_suspend,
+    .runtime_resume = bbswitch_runtime_resume,
+    /* No runtime_idle callback, the default zero delay is sufficient. */
+};
+
+static struct pci_driver bbswitch_pci_driver = {
+    .name = KBUILD_MODNAME,
+    .id_table = NULL, /* will be added dynamically */
+    .probe  = bbswitch_pci_probe,
+    .remove = bbswitch_pci_remove,
+    .driver.pm = &bbswitch_pm_ops,
+};
+
+static int __init bbswitch_dev_init(void) {
+    int ret;
+
+    ret = pci_register_driver(&bbswitch_pci_driver);
+#if 0
+    ret = pci_add_dynid(&bbswitch_pci_driver, PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
+            PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY << 16, 0xff0000);
+#endif
+
+    return ret;
+}
+
+static void __exit bbswitch_dev_exit(void) {
+    pci_unregister_driver(&bbswitch_pci_driver);
+}
+
+module_init(bbswitch_dev_init);
+module_exit(bbswitch_dev_exit);
+
+/* vim: set sw=4 ts=4 et: */