drm/bridge: fsl-ldb: Drop DE signal polarity inversion

It's unnecessary to invert input data enable signal polarity
according to the output one. Let's drop the inversion.
Since ->atomic_check() does nothing more than the inversion,
it can be dropped entirely as well.

Without this patch, 'koe,tx26d202vm0bwa' LVDS panel connected
with i.MX8MP EVK board does not show any data on screen.

Fixes: 463db5c ("drm: bridge: ldb: Implement simple Freescale i.MX8MP LDB bridge")
Cc: Andrzej Hajda <[email protected]>
Cc: Neil Armstrong <[email protected]>
Cc: Robert Foss <[email protected]>
Cc: Laurent Pinchart <[email protected]>
Cc: Jonas Karlman <[email protected]>
Cc: Jernej Skrabec <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Cc: Marek Vasut <[email protected]>
Cc: NXP Linux Team <[email protected]>
Signed-off-by: Liu Ying <[email protected]>
Reviewed-by: Marek Vasut <[email protected]>
Signed-off-by: Neil Armstrong <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Liu Ying

drivers/gpu/drm/bridge/fsl-ldb.c

@@ -74,22 +74,6 @@ static int fsl_ldb_attach(struct drm_bridge *bridge,
 				 bridge, flags);
 }
 
-static int fsl_ldb_atomic_check(struct drm_bridge *bridge,
-				struct drm_bridge_state *bridge_state,
-				struct drm_crtc_state *crtc_state,
-				struct drm_connector_state *conn_state)
-{
-	/* Invert DE signal polarity. */
-	bridge_state->input_bus_cfg.flags &= ~(DRM_BUS_FLAG_DE_LOW |
-					       DRM_BUS_FLAG_DE_HIGH);
-	if (bridge_state->output_bus_cfg.flags & DRM_BUS_FLAG_DE_LOW)
-		bridge_state->input_bus_cfg.flags |= DRM_BUS_FLAG_DE_HIGH;
-	else if (bridge_state->output_bus_cfg.flags & DRM_BUS_FLAG_DE_HIGH)
-		bridge_state->input_bus_cfg.flags |= DRM_BUS_FLAG_DE_LOW;
-
-	return 0;
-}
-
 static void fsl_ldb_atomic_enable(struct drm_bridge *bridge,
 				  struct drm_bridge_state *old_bridge_state)
 {
@@ -241,7 +225,6 @@ fsl_ldb_mode_valid(struct drm_bridge *bridge,
 
 static const struct drm_bridge_funcs funcs = {
 	.attach = fsl_ldb_attach,
-	.atomic_check = fsl_ldb_atomic_check,
 	.atomic_enable = fsl_ldb_atomic_enable,
 	.atomic_disable = fsl_ldb_atomic_disable,
 	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,