ACPIPHP / radeon / nouveau: Fix VGA switcheroo problem related to hotplug

The changes in the ACPI-based PCI hotplug (ACPIPHP) subsystem made
during the 3.12 development cycle uncovered a problem with VGA
switcheroo that on some systems, when the device-specific method
(ATPX in the radeon case, _DSM in the nouveau case) is used to turn
off the discrete graphics, the BIOS generates ACPI hotplug events for
that device and those events cause ACPIPHP to attempt to remove the
device from the system (they are events for a device that was present
previously and is not present any more, so that's what should be done
according to the spec).  Then, the system stops functioning correctly.

Since the hotplug events in question were simply silently ignored
previously, the least intrusive way to address that problem is to
make ACPIPHP ignore them again.  For this purpose, introduce a new
ACPI device flag, no_hotplug, and modify ACPIPHP to ignore hotplug
events for PCI devices whose ACPI companions have that flag set.
Next, make the radeon and nouveau switcheroo detection code set the
no_hotplug flag for the discrete graphics' ACPI companion.

Fixes: bbd34fcdd1b2 (ACPI / hotplug / PCI: Register all devices under the given bridge)
References: https://bugzilla.kernel.org/show_bug.cgi?id=61891
References: https://bugzilla.kernel.org/show_bug.cgi?id=64891
Reported-and-tested-by: Mike Lothian <mike@fireburn.co.uk>
Reported-and-tested-by: <madcatx@atlas.cz>
Reported-and-tested-by: Joaquín Aramendía <samsagax@gmail.com>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: 3.12+ <stable@vger.kernel.org> # 3.12+

1 files changed, 23 insertions, 3 deletions

diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
index 438a4d09958..e86439283a5 100644
--- a/drivers/pci/hotplug/acpiphp_glue.c
+++ b/drivers/pci/hotplug/acpiphp_glue.c
@@ -645,6 +645,24 @@ static void disable_slot(struct acpiphp_slot *slot)
 	slot->flags &= (~SLOT_ENABLED);
 }
 
+static bool acpiphp_no_hotplug(acpi_handle handle)
+{
+	struct acpi_device *adev = NULL;
+
+	acpi_bus_get_device(handle, &adev);
+	return adev && adev->flags.no_hotplug;
+}
+
+static bool slot_no_hotplug(struct acpiphp_slot *slot)
+{
+	struct acpiphp_func *func;
+
+	list_for_each_entry(func, &slot->funcs, sibling)
+		if (acpiphp_no_hotplug(func_to_handle(func)))
+			return true;
+
+	return false;
+}
 
 /**
  * get_slot_status - get ACPI slot status
@@ -703,7 +721,8 @@ static void trim_stale_devices(struct pci_dev *dev)
 		unsigned long long sta;
 
 		status = acpi_evaluate_integer(handle, "_STA", NULL, &sta);
-		alive = ACPI_SUCCESS(status) && sta == ACPI_STA_ALL;
+		alive = (ACPI_SUCCESS(status) && sta == ACPI_STA_ALL)
+			|| acpiphp_no_hotplug(handle);
 	}
 	if (!alive) {
 		u32 v;
@@ -743,8 +762,9 @@ static void acpiphp_check_bridge(struct acpiphp_bridge *bridge)
 		struct pci_dev *dev, *tmp;
 
 		mutex_lock(&slot->crit_sect);
-		/* wake up all functions */
-		if (get_slot_status(slot) == ACPI_STA_ALL) {
+		if (slot_no_hotplug(slot)) {
+			; /* do nothing */
+		} else if (get_slot_status(slot) == ACPI_STA_ALL) {
 			/* remove stale devices if any */
 			list_for_each_entry_safe(dev, tmp, &bus->devices,
 						 bus_list)