drm/amdgpu: Add amdgpu_atpx_get_dhandle()

Since it seems that some vendors are storing the ATIF ACPI methods under
the same handle that ATPX lives under instead of the device's own
handle, we're going to need to be able to retrieve this handle later so
we can probe for ATIF there.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -1858,6 +1858,12 @@ static inline bool amdgpu_atpx_dgpu_req_power_for_displays(void) { return false;
 static inline bool amdgpu_has_atpx(void) { return false; }
 #endif
 
+#if defined(CONFIG_VGA_SWITCHEROO) && defined(CONFIG_ACPI)
+void *amdgpu_atpx_get_dhandle(void);
+#else
+static inline void *amdgpu_atpx_get_dhandle(void) { return NULL; }
+#endif
+
 /*
  * KMS
  */

drivers/gpu/drm/amd/amdgpu/amdgpu_atpx_handler.c

@@ -90,6 +90,12 @@ bool amdgpu_atpx_dgpu_req_power_for_displays(void) {
 	return amdgpu_atpx_priv.atpx.dgpu_req_power_for_displays;
 }
 
+#if defined(CONFIG_ACPI)
+void *amdgpu_atpx_get_dhandle(void) {
+	return amdgpu_atpx_priv.dhandle;
+}
+#endif
+
 /**
  * amdgpu_atpx_call - call an ATPX method
  *