Commit f64e4275 authored by Hans de Goede's avatar Hans de Goede Committed by Rafael J. Wysocki
Browse files

ACPI: Fix selecting wrong ACPI fwnode for the iGPU on some Dell laptops 



The Dell Latitude E6430 both with and without the optional NVidia dGPU
has a bug in its ACPI tables which is causing Linux to assign the wrong
ACPI fwnode / companion to the pci_device for the i915 iGPU.

Specifically under the PCI root bridge there are these 2 ACPI Device()s :

 Scope (_SB.PCI0)
 {
     Device (GFX0)
     {
         Name (_ADR, 0x00020000)  // _ADR: Address
     }

     ...

     Device (VID)
     {
         Name (_ADR, 0x00020000)  // _ADR: Address
         ...

         Method (_DOS, 1, NotSerialized)  // _DOS: Disable Output Switching
         {
             VDP8 = Arg0
             VDP1 (One, VDP8)
         }

         Method (_DOD, 0, NotSerialized)  // _DOD: Display Output Devices
         {
             ...
         }
         ...
     }
 }

The non-functional GFX0 ACPI device is a problem, because this gets
returned as ACPI companion-device by acpi_find_child_device() for the iGPU.

This is a long standing problem and the i915 driver does use the ACPI
companion for some things, but works fine without it.

However since commit 63f534b8 ("ACPI: PCI: Rework acpi_get_pci_dev()")
acpi_get_pci_dev() relies on the physical-node pointer in the acpi_device
and that is set on the wrong acpi_device because of the wrong
acpi_find_child_device() return. This breaks the ACPI video code,
leading to non working backlight control in some cases.

Add a type.backlight flag, mark ACPI video bus devices with this and make
find_child_checks() return a higher score for children with this flag set,
so that it picks the right companion-device.

Fixes: 63f534b8 ("ACPI: PCI: Rework acpi_get_pci_dev()")
Co-developed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
Cc: 6.1+ <stable@vger.kernel.org> # 6.1+
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent b7bfaa76

drivers/acpi/glue.c

+12 −2
Original line number Diff line number Diff line
@@ -75,7 +75,8 @@ static struct acpi_bus_type *acpi_get_bus_type(struct device *dev) 
}



#define FIND_CHILD_MIN_SCORE	1

#define FIND_CHILD_MAX_SCORE	2

#define FIND_CHILD_MID_SCORE	2

#define FIND_CHILD_MAX_SCORE	3



static int match_any(struct acpi_device *adev, void *not_used)

{
@@ -96,8 +97,17 @@ static int find_child_checks(struct acpi_device *adev, bool check_children) 
		return -ENODEV;



	status = acpi_evaluate_integer(adev->handle, "_STA", NULL, &sta);

	if (status == AE_NOT_FOUND)

	if (status == AE_NOT_FOUND) {

		/*

		 * Special case: backlight device objects without _STA are

		 * preferred to other objects with the same _ADR value, because

		 * it is more likely that they are actually useful.

		 */

		if (adev->pnp.type.backlight)

			return FIND_CHILD_MID_SCORE;



		return FIND_CHILD_MIN_SCORE;

	}



	if (ACPI_FAILURE(status) || !(sta & ACPI_STA_DEVICE_ENABLED))

		return -ENODEV;

drivers/acpi/scan.c

+5 −2
Original line number Diff line number Diff line
@@ -1370,9 +1370,12 @@ static void acpi_set_pnp_ids(acpi_handle handle, struct acpi_device_pnp *pnp, 
		 * Some devices don't reliably have _HIDs & _CIDs, so add

		 * synthetic HIDs to make sure drivers can find them.

		 */

		if (acpi_is_video_device(handle))

		if (acpi_is_video_device(handle)) {

			acpi_add_id(pnp, ACPI_VIDEO_HID);

		else if (acpi_bay_match(handle))

			pnp->type.backlight = 1;

			break;

		}

		if (acpi_bay_match(handle))

			acpi_add_id(pnp, ACPI_BAY_HID);

		else if (acpi_dock_match(handle))

			acpi_add_id(pnp, ACPI_DOCK_HID);

include/acpi/acpi_bus.h

+2 −1
Original line number Diff line number Diff line
@@ -230,7 +230,8 @@ struct acpi_pnp_type { 
	u32 hardware_id:1;

	u32 bus_address:1;

	u32 platform_id:1;

	u32 reserved:29;

	u32 backlight:1;

	u32 reserved:28;

};



struct acpi_device_pnp {