linux-kernel - [PATCH 08/10] drm: bridge: it66121: Set DDC preamble only once before reading EDID

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Date:   Wed, 14 Dec 2022 13:58:19 +0100
From:   Paul Cercueil <paul@...pouillou.net>
To:     Phong LE <ple@...libre.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     list@...ndingux.net, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Paul Cercueil <paul@...pouillou.net>
Subject: [PATCH 08/10] 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@...pouillou.net>
---
 drivers/gpu/drm/bridge/ite-it66121.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it66121.c b/drivers/gpu/drm/bridge/ite-it66121.c
index 5335d4abd7c5..7972003d4776 100644
--- a/drivers/gpu/drm/bridge/ite-it66121.c
+++ b/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;
-- 
2.35.1