drm/i915: Recognise non-VGA display devices

Starting with SandyBridge (though possible with earlier hacked BIOSes),
the BIOS may initialise the IGFX as secondary to a discrete GPU. Prior,
it would simply disable the integrated GPU. So we adjust our PCI class
mask to match any DISPLAY_CLASS device.

In such a configuration, the IGFX is not a primary VGA controller and
so should not take part in VGA arbitration, and the error return from
vga_client_register() is expected.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 665898124200..17bd766f2081 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1215,9 +1215,15 @@ static int i915_load_modeset_init(struct drm_device *dev)
         if (ret)
                 DRM_INFO("failed to find VBIOS tables\n");
 
-        /* if we have > 1 VGA cards, then disable the radeon VGA resources */
+        /* If we have > 1 VGA cards, then we need to arbitrate access
+         * to the common VGA resources.
+         *
+         * If we are a secondary display controller (!PCI_DISPLAY_CLASS_VGA),
+         * then we do not take part in VGA arbitration and the
+         * vga_client_register() fails with -ENODEV.
+         */
         ret = vga_client_register(dev->pdev, dev, NULL, i915_vga_set_decode);
-        if (ret)
+        if (ret && ret != -ENODEV)
                 goto cleanup_ringbuffer;
 
         intel_register_dsm_handler();