From DT point of view, in general, drivers should be asking for a
specific port number because their function is fixed in the binding.

of_graph_get_next_endpoint() doesn't match to this concept.

Simply replace

        - of_graph_get_next_endpoint(xxx, NULL);
        + of_graph_get_endpoint_by_regs(xxx, 0, -1);

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/drm_of.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index 5c2abc9eca9c2..5530919e0ba05 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -564,6 +564,8 @@ EXPORT_SYMBOL_GPL(drm_of_get_data_lanes_count_ep);
  * Gets parent DSI bus for a DSI device controlled through a bus other
  * than MIPI-DCS (SPI, I2C, etc.) using the Device Tree.
  *
+ * This function assumes that the device's port@0 is the DSI input.
+ *
  * Returns pointer to mipi_dsi_host if successful, -EINVAL if the
  * request is unsupported, -EPROBE_DEFER if the DSI host is found but
  * not available, or -ENODEV otherwise.
@@ -576,7 +578,7 @@ struct mipi_dsi_host *drm_of_get_dsi_bus(struct device *dev)
 	/*
 	 * Get first endpoint child from device.
 	 */
-	endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
+	endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 0, -1);
 	if (!endpoint)
 		return ERR_PTR(-ENODEV);
 
-- 
2.43.0