Implement .atomic_check callback which prevents user space from setting
unsupported mode. The tc_edp_common_atomic_check() variant is already
prepared for DSI-to-DPI mode addition, which has different frequency
limits.

Signed-off-by: Marek Vasut <ma...@denx.de>
Cc: Jonas Karlman <jo...@kwiboo.se>
Cc: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
Cc: Maxime Ripard <max...@cerno.tech>
Cc: Neil Armstrong <narmstr...@baylibre.com>
Cc: Sam Ravnborg <s...@ravnborg.org>
---
V2: - New patch
---
 drivers/gpu/drm/bridge/tc358767.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/bridge/tc358767.c 
b/drivers/gpu/drm/bridge/tc358767.c
index 522c2c4d8514f..01d11adee6c74 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -1289,6 +1289,31 @@ static bool tc_bridge_mode_fixup(struct drm_bridge 
*bridge,
        return true;
 }
 
+static int tc_edp_common_atomic_check(struct drm_bridge *bridge,
+                                     struct drm_bridge_state *bridge_state,
+                                     struct drm_crtc_state *crtc_state,
+                                     struct drm_connector_state *conn_state,
+                                     const unsigned int max_khz)
+{
+       tc_bridge_mode_fixup(bridge, &crtc_state->mode,
+                            &crtc_state->adjusted_mode);
+
+       if (crtc_state->adjusted_mode.clock > max_khz)
+               crtc_state->adjusted_mode.clock = max_khz;
+
+       return 0;
+}
+
+static int tc_edp_atomic_check(struct drm_bridge *bridge,
+                              struct drm_bridge_state *bridge_state,
+                              struct drm_crtc_state *crtc_state,
+                              struct drm_connector_state *conn_state)
+{
+       /* DPI->(e)DP interface clock limitation: upto 154 MHz */
+       return tc_edp_common_atomic_check(bridge, bridge_state, crtc_state,
+                                         conn_state, 154000);
+}
+
 static enum drm_mode_status
 tc_edp_mode_valid(struct drm_bridge *bridge,
                  const struct drm_display_info *info,
@@ -1463,6 +1488,7 @@ static const struct drm_bridge_funcs tc_bridge_funcs = {
        .detach = tc_edp_bridge_detach,
        .mode_valid = tc_edp_mode_valid,
        .mode_set = tc_bridge_mode_set,
+       .atomic_check = tc_edp_atomic_check,
        .atomic_enable = tc_edp_bridge_atomic_enable,
        .atomic_disable = tc_edp_bridge_atomic_disable,
        .mode_fixup = tc_bridge_mode_fixup,
-- 
2.34.1

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