drm/bridge: synopsys: dw-mipi-dsi: Force input bus flags

The DATAEN_ACTIVE_LOW bit in DSI_DPI_CFG_POL register is set to zero,
so set the DRM_BUS_FLAG_DE_HIGH flag in input_bus_cfg.flags.  It appears
that the DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE flag also makes sense, so
set it in input_bus_cfg.flags too.  With this patch, the flags set by
drm_atomic_bridge_propagate_bus_flags() are overridden (see comment in
that function) in case any downstream bridges propagates invalid flags
to this bridge.  A real problematic case is to connect a RM67191 MIPI
DSI panel whose driver sets DRM_BUS_FLAG_DE_LOW and
DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE bus flags.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230821034008.3876938-4-victor.liu@nxp.com

drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c

@@ -23,6 +23,7 @@
 #include <drm/bridge/dw_mipi_dsi.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_bridge.h>
+#include <drm/drm_connector.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_modes.h>
@@ -567,6 +568,17 @@ dw_mipi_dsi_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
 	return input_fmts;
 }
 
+static int dw_mipi_dsi_bridge_atomic_check(struct drm_bridge *bridge,
+					   struct drm_bridge_state *bridge_state,
+					   struct drm_crtc_state *crtc_state,
+					   struct drm_connector_state *conn_state)
+{
+	bridge_state->input_bus_cfg.flags =
+		DRM_BUS_FLAG_DE_HIGH | DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE;
+
+	return 0;
+}
+
 static void dw_mipi_dsi_video_mode_config(struct dw_mipi_dsi *dsi)
 {
 	u32 val;
@@ -1036,6 +1048,7 @@ static const struct drm_bridge_funcs dw_mipi_dsi_bridge_funcs = {
 	.atomic_duplicate_state	= drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state	= drm_atomic_helper_bridge_destroy_state,
 	.atomic_get_input_bus_fmts = dw_mipi_dsi_bridge_atomic_get_input_bus_fmts,
+	.atomic_check		= dw_mipi_dsi_bridge_atomic_check,
 	.atomic_reset		= drm_atomic_helper_bridge_reset,
 	.atomic_pre_enable	= dw_mipi_dsi_bridge_atomic_pre_enable,
 	.atomic_enable		= dw_mipi_dsi_bridge_atomic_enable,