drm/nvd0/disp: dac load detect

VBIOS does more than this, as does nv50/nvc0 driver in nouveau.  Traces
of the NVIDIA binary driver however, show pretty much just this being
done...  Seems to work for me, it'll be fine for the moment.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/gpu/drm/nouveau/nvd0_display.c b/drivers/gpu/drm/nouveau/nvd0_display.c
index 6720d63cfccc..f4788d819ed6 100644
--- a/drivers/gpu/drm/nouveau/nvd0_display.c
+++ b/drivers/gpu/drm/nouveau/nvd0_display.c
@@ -685,7 +685,22 @@ nvd0_dac_disconnect(struct drm_encoder *encoder)
 static enum drm_connector_status
 nvd0_dac_detect(struct drm_encoder *encoder, struct drm_connector *connector)
 {
-        return connector_status_disconnected;
+        enum drm_connector_status status = connector_status_disconnected;
+        struct nouveau_encoder *nv_encoder = nouveau_encoder(encoder);
+        struct drm_device *dev = encoder->dev;
+        int or = nv_encoder->or;
+        u32 load;
+
+        nv_wr32(dev, 0x61a00c + (or * 0x800), 0x00100000);
+        udelay(9500);
+        nv_wr32(dev, 0x61a00c + (or * 0x800), 0x80000000);
+
+        load = nv_rd32(dev, 0x61a00c + (or * 0x800));
+        if ((load & 0x38000000) == 0x38000000)
+                status = connector_status_connected;
+
+        nv_wr32(dev, 0x61a00c + (or * 0x800), 0x00000000);
+        return status;
 }
 
 static void