drm: bridge: it66121: Set DDC preamble only once before reading EDID

The DDC preamble and target address only need to be set once before
reading the EDID, even if multiple segments have to be read.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221214125821.12489-9-paul@crapouillou.net

drivers/gpu/drm/bridge/ite-it66121.c

@@ -506,9 +506,6 @@ static int it66121_get_edid_block(void *context, u8 *buf,
 	while (remain > 0) {
 		cnt = (remain > IT66121_EDID_FIFO_SIZE) ?
 				IT66121_EDID_FIFO_SIZE : remain;
-		ret = it66121_preamble_ddc(ctx);
-		if (ret)
-			return ret;
 
 		ret = regmap_write(ctx->regmap, IT66121_DDC_COMMAND_REG,
 				   IT66121_DDC_COMMAND_FIFO_CLR);
@@ -519,15 +516,6 @@ static int it66121_get_edid_block(void *context, u8 *buf,
 		if (ret)
 			return ret;
 
-		ret = it66121_preamble_ddc(ctx);
-		if (ret)
-			return ret;
-
-		ret = regmap_write(ctx->regmap, IT66121_DDC_HEADER_REG,
-				   IT66121_DDC_HEADER_EDID);
-		if (ret)
-			return ret;
-
 		ret = regmap_write(ctx->regmap, IT66121_DDC_OFFSET_REG, offset);
 		if (ret)
 			return ret;
@@ -842,9 +830,25 @@ static struct edid *it66121_bridge_get_edid(struct drm_bridge *bridge,
 {
 	struct it66121_ctx *ctx = container_of(bridge, struct it66121_ctx, bridge);
 	struct edid *edid;
+	int ret;
 
 	mutex_lock(&ctx->lock);
+	ret = it66121_preamble_ddc(ctx);
+	if (ret) {
+		edid = ERR_PTR(ret);
+		goto out_unlock;
+	}
+
+	ret = regmap_write(ctx->regmap, IT66121_DDC_HEADER_REG,
+			   IT66121_DDC_HEADER_EDID);
+	if (ret) {
+		edid = ERR_PTR(ret);
+		goto out_unlock;
+	}
+
 	edid = drm_do_get_edid(connector, it66121_get_edid_block, ctx);
+
+out_unlock:
 	mutex_unlock(&ctx->lock);
 
 	return edid;