drm/bridge: lt9611uxc: support displays with up to 4 EDID blocks

drivers/gpu/drm/bridge/lontium-lt9611uxc.c

@@ -28,7 +28,7 @@
 #include <drm/display/drm_hdmi_audio_helper.h>
 
 #define EDID_BLOCK_SIZE	128
-#define EDID_NUM_BLOCKS	2
+#define EDID_NUM_BLOCKS	4
 
 #define FW_FILE "lt9611uxc_fw.bin"
 
@@ -171,10 +171,9 @@ static void lt9611uxc_hpd_work(struct work_struct *work)
 
 	mutex_lock(&lt9611uxc->ocm_lock);
 	connected = lt9611uxc->hdmi_connected;
-	mutex_unlock(&lt9611uxc->ocm_lock);
-
 	if (!connected)
 		lt9611uxc->edid_read = false;
+	mutex_unlock(&lt9611uxc->ocm_lock);
 
 	drm_bridge_hpd_notify(&lt9611uxc->bridge,
 			      connected ?
@@ -392,31 +391,85 @@ static int lt9611uxc_wait_for_edid(struct lt9611uxc *lt9611uxc)
 			msecs_to_jiffies(1000));
 }
 
+static int lt9611uxc_read_edid_block(struct lt9611uxc *lt9611uxc, unsigned int block,
+				     u8 *buf,  size_t len)
+{
+	int ret;
+
+	lt9611uxc_lock(lt9611uxc);
+
+	regmap_write(lt9611uxc->regmap, 0xb00a, (block % 2) * EDID_BLOCK_SIZE);
+
+	ret = regmap_noinc_read(lt9611uxc->regmap, 0xb0b0, buf, len);
+	if (ret) {
+		dev_err(lt9611uxc->dev, "edid block %d read failed: %d\n", block, ret);
+		lt9611uxc_unlock(lt9611uxc);
+		return -EINVAL;
+	}
+	lt9611uxc_unlock(lt9611uxc);
+
+	return ret;
+}
+
 static int lt9611uxc_get_edid_block(void *data, u8 *buf, unsigned int block, size_t len)
 {
 	struct lt9611uxc *lt9611uxc = data;
-	int ret;
+	int ret = 0;
+	int retry_cnt = 10;
+	unsigned int edid_ready_flag = 0;
+	bool header_matched;
+	bool edid_valid = false;
+	const u8 edid_header[8] = { 0x00, 0xFF, 0xFF, 0xFF,
+				    0xFF, 0xFF, 0xFF, 0x00 };
 
 	if (len > EDID_BLOCK_SIZE)
 		return -EINVAL;
 
 	if (block >= EDID_NUM_BLOCKS)
 		return -EINVAL;
 
-	lt9611uxc_lock(lt9611uxc);
+	if (block == 0 || block == 2) {
 
-	regmap_write(lt9611uxc->regmap, 0xb00b, 0x10);
+		lt9611uxc_lock(lt9611uxc);
 
-	regmap_write(lt9611uxc->regmap, 0xb00a, block * EDID_BLOCK_SIZE);
+		edid_ready_flag = (block == 0) ? BIT(0) : BIT(1);
 
-	ret = regmap_noinc_read(lt9611uxc->regmap, 0xb0b0, buf, len);
-	if (ret)
-		dev_err(lt9611uxc->dev, "edid read failed: %d\n", ret);
+		/*
+		 * Set the EDID ready flag so that lt9611uxc can fetch correct EDID block
+		 */
+		regmap_write(lt9611uxc->regmap, 0xb028, edid_ready_flag);
 
-	lt9611uxc_unlock(lt9611uxc);
+		lt9611uxc_unlock(lt9611uxc);
 
-	return 0;
-};
+		do {
+			msleep(100);
+			ret = lt9611uxc_read_edid_block(lt9611uxc, block, buf, len);
+			if (ret)
+				break;
+			/*
+			 * Compare first 8 bytes of EDID header for block 0 and block 2
+			 * to confirm EDID read successfully
+			 */
+			header_matched = (memcmp(edid_header, buf, 8) == 0);
+			edid_valid = (block == 0 && header_matched) ||
+				     (block == 2 && !header_matched);
+			if (edid_valid)
+				break;
+
+		} while (retry_cnt-- > 0);
+
+		if (!ret && !edid_valid)
+			ret = -ETIMEDOUT;
+	} else {
+		ret = lt9611uxc_read_edid_block(lt9611uxc, block, buf, len);
+
+		lt9611uxc_lock(lt9611uxc);
+		regmap_write(lt9611uxc->regmap, 0xb028, 0x00);
+		lt9611uxc_unlock(lt9611uxc);
+	}
+
+	return ret;
+}
 
 static const struct drm_edid *lt9611uxc_bridge_edid_read(struct drm_bridge *bridge,
 							 struct drm_connector *connector)