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+
diff --git a/drivers/gpu/drm/radeon/radeon_atpx_handler.c b/drivers/gpu/drm/radeon/radeon_atpx_handler.c
index 9d302ea..485848f 100644
--- a/drivers/gpu/drm/radeon/radeon_atpx_handler.c
+++ b/drivers/gpu/drm/radeon/radeon_atpx_handler.c
@@ -33,6 +33,7 @@
bool atpx_detected;
/* handle for device - and atpx */
acpi_handle dhandle;
+ acpi_handle other_handle;
struct radeon_atpx atpx;
} radeon_atpx_priv;
@@ -451,9 +452,10 @@
return false;
status = acpi_get_handle(dhandle, "ATPX", &atpx_handle);
- if (ACPI_FAILURE(status))
+ if (ACPI_FAILURE(status)) {
+ radeon_atpx_priv.other_handle = dhandle;
return false;
-
+ }
radeon_atpx_priv.dhandle = dhandle;
radeon_atpx_priv.atpx.handle = atpx_handle;
return true;
@@ -530,6 +532,16 @@
printk(KERN_INFO "VGA switcheroo: detected switching method %s handle\n",
acpi_method_name);
radeon_atpx_priv.atpx_detected = true;
+ /*
+ * On some systems hotplug events are generated for the device
+ * being switched off when ATPX is executed. They cause ACPI
+ * hotplug to trigger and attempt to remove the device from
+ * the system, which causes it to break down. Prevent that from
+ * happening by setting the no_hotplug flag for the involved
+ * ACPI device objects.
+ */
+ acpi_bus_no_hotplug(radeon_atpx_priv.dhandle);
+ acpi_bus_no_hotplug(radeon_atpx_priv.other_handle);
return true;
}
return false;