[PATCH v6 3/8] drm/bridge: mhdp8546: Add minimal format negotiation

[Aradhya Bhatia <a-bhatia1@ti.com>]

From: Nikhil Devshatwar <nikhil.nd@ti.com>

With new connector model, mhdp bridge will not create the connector and
SoC driver will rely on format negotiation to setup the encoder format.

Support minimal format negotiations hooks in the drm_bridge_funcs.
Complete format negotiation can be added based on EDID data.
This patch adds the minimal required support to avoid failure
after moving to new connector model.

Signed-off-by: Nikhil Devshatwar <nikhil.nd@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
---

Notes:

    changes from v1:
    * cosmetic fixes, commit message update.

    changes from v5:
    * dropped the default_bus_format variable and directly assigned
      MEDIA_BUS_FMT_RGB121212_1X36 to input_fmts.

 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index f6822dfa3805..623e4235c94f 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -2146,6 +2146,30 @@ cdns_mhdp_bridge_atomic_reset(struct drm_bridge *bridge)
 	return &cdns_mhdp_state->base;
 }
 
+static u32 *cdns_mhdp_get_input_bus_fmts(struct drm_bridge *bridge,
+					 struct drm_bridge_state *bridge_state,
+					 struct drm_crtc_state *crtc_state,
+					 struct drm_connector_state *conn_state,
+					 u32 output_fmt,
+					 unsigned int *num_input_fmts)
+{
+	u32 *input_fmts;
+
+	*num_input_fmts = 0;
+
+	if (output_fmt != MEDIA_BUS_FMT_FIXED)
+		return NULL;
+
+	input_fmts = kzalloc(sizeof(*input_fmts), GFP_KERNEL);
+	if (!input_fmts)
+		return NULL;
+
+	*num_input_fmts = 1;
+	input_fmts[0] = MEDIA_BUS_FMT_RGB121212_1X36;
+
+	return input_fmts;
+}
+
 static int cdns_mhdp_atomic_check(struct drm_bridge *bridge,
 				  struct drm_bridge_state *bridge_state,
 				  struct drm_crtc_state *crtc_state,
@@ -2210,6 +2234,7 @@ static const struct drm_bridge_funcs cdns_mhdp_bridge_funcs = {
 	.atomic_duplicate_state = cdns_mhdp_bridge_atomic_duplicate_state,
 	.atomic_destroy_state = cdns_mhdp_bridge_atomic_destroy_state,
 	.atomic_reset = cdns_mhdp_bridge_atomic_reset,
+	.atomic_get_input_bus_fmts = cdns_mhdp_get_input_bus_fmts,
 	.detect = cdns_mhdp_bridge_detect,
 	.get_edid = cdns_mhdp_bridge_get_edid,
 	.hpd_enable = cdns_mhdp_bridge_hpd_enable,
-- 
2.40.1