[PATCH 3/8] drm/bridge/synopsys: dsi: defer probing if panel not available in bridge-attach

[Heiko Stuebner <heiko@sntech.de>]

When the panel-driver is build as a module it currently fails hard as the
panel cannot be probed directly:

dw_mipi_dsi_bind()
  __dw_mipi_dsi_probe()
    creates dsi bus
    creates panel device
    triggers panel module load
    panel not probed (module not loaded or panel probe slow)
  drm_bridge_attach
    fails with -EINVAL due to empty panel_bridge

So emit a -EPROBE_DEFER in that case to give the driver another
chance at getting the display later.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
---
 drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
index 691f67bc2ff9..1b4f6bb7ea59 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -839,6 +839,9 @@ static int dw_mipi_dsi_bridge_attach(struct drm_bridge *bridge)
 		return -ENODEV;
 	}
 
+	if (!dsi->panel_bridge)
+		return -EPROBE_DEFER;
+
 	/* Set the encoder type as caller does not know it */
 	bridge->encoder->encoder_type = DRM_MODE_ENCODER_DSI;
 
-- 
2.17.0

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