drm/nouveau/kms/nv50-: Just use drm_dp_dpcd_read() in nouveau_dp.c

Since this actually logs accesses, we should probably always be using
this imho…

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ben Skeggs <bskeggs@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200826182456.322681-4-lyude@redhat.com

drivers/gpu/drm/nouveau/nouveau_dp.c

@@ -42,16 +42,12 @@ nouveau_dp_detect(struct nouveau_connector *nv_connector,
 {
 	struct drm_device *dev = nv_encoder->base.base.dev;
 	struct nouveau_drm *drm = nouveau_drm(dev);
-	struct nvkm_i2c_aux *aux;
-	u8 dpcd[8];
+	struct drm_dp_aux *aux = &nv_connector->aux;
+	u8 dpcd[DP_RECEIVER_CAP_SIZE];
 	int ret;
 
-	aux = nv_encoder->aux;
-	if (!aux)
-		return -ENODEV;
-
-	ret = nvkm_rdaux(aux, DP_DPCD_REV, dpcd, sizeof(dpcd));
-	if (ret)
+	ret = drm_dp_dpcd_read(aux, DP_DPCD_REV, dpcd, DP_RECEIVER_CAP_SIZE);
+	if (ret != sizeof(dpcd))
 		return ret;
 
 	nv_encoder->dp.link_bw = 27000 * dpcd[1];