[PATCH v2 4/6] drm/tidss: Set bus_format correctly from bridge/connector

[Nikhil Devshatwar <nikhil.nd@xxxxxx>]

When there is a chain of bridges attached to the encoder,
the bus_format should be ideally set from the input format of the
first bridge in the chain.

Use the bridge state to get the negotiated bus_format.
If the bridge does not support format negotiation, error out
and fail.

Signed-off-by: Nikhil Devshatwar <nikhil.nd@xxxxxx>
---
 drivers/gpu/drm/tidss/tidss_encoder.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/tidss/tidss_encoder.c b/drivers/gpu/drm/tidss/tidss_encoder.c
index e278a9c89476..ba5b6fccabe7 100644
--- a/drivers/gpu/drm/tidss/tidss_encoder.c
+++ b/drivers/gpu/drm/tidss/tidss_encoder.c
@@ -22,6 +22,7 @@ static int tidss_encoder_atomic_check(struct drm_encoder *encoder,
 	struct drm_device *ddev = encoder->dev;
 	struct tidss_crtc_state *tcrtc_state = to_tidss_crtc_state(crtc_state);
 	struct drm_display_info *di = &conn_state->connector->display_info;
+	struct drm_bridge_state *bstate;
 	struct drm_bridge *bridge;
 	bool bus_flags_set = false;
 
@@ -41,17 +42,22 @@ static int tidss_encoder_atomic_check(struct drm_encoder *encoder,
 		break;
 	}
 
-	if (!di->bus_formats || di->num_bus_formats == 0)  {
-		dev_err(ddev->dev, "%s: No bus_formats in connected display\n",
-			__func__);
-		return -EINVAL;
-	}
-
-	// XXX any cleaner way to set bus format and flags?
-	tcrtc_state->bus_format = di->bus_formats[0];
 	if (!bus_flags_set)
 		tcrtc_state->bus_flags = di->bus_flags;
 
+	/* Copy the bus_format from the input_bus_format of first bridge */
+	bridge = drm_bridge_chain_get_first_bridge(encoder);
+	bstate = drm_atomic_get_new_bridge_state(crtc_state->state, bridge);
+	if (bstate)
+		tcrtc_state->bus_format = bstate->input_bus_cfg.format;
+
+	if (tcrtc_state->bus_format == 0 ||
+	    tcrtc_state->bus_format == MEDIA_BUS_FMT_FIXED) {
+
+		dev_err(ddev->dev, "Bridge connected to the encoder did not specify media bus format\n");
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
-- 
2.17.1

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