linux-kernel - [PATCH] drm/bridge: ti-sn65dsi83: Support LVDS Channel B on SN65DSI84

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Message-Id: <20250502-sn65dsi83-channel-swap-v1-1-0738be9b27ab@geanix.com>
Date: Fri, 02 May 2025 16:41:23 +0200
From: Esben Haabendal <esben@...nix.com>
To: Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Marek Vasut <marex@...x.de>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Esben Haabendal <esben@...nix.com>
Subject: [PATCH] drm/bridge: ti-sn65dsi83: Support LVDS Channel B on
 SN65DSI84

This adds support for using SN65DSI84 in single-link mode with output to
LVDS Channel B.

Signed-off-by: Esben Haabendal <esben@...nix.com>
---
 drivers/gpu/drm/bridge/ti-sn65dsi83.c | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index 95563aa1b450d549be8cacbe58c45f07b93595e5..e5785447c804eeced24f80c2b8b90283623c86a9 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -11,6 +11,8 @@
  *   = 1x Single-link DSI ~ 2x Single-link or 1x Dual-link LVDS
  *   - Supported
  *   - Dual-link LVDS mode tested
+ *   - Single-link to LVDS Channel A tested.
+ *   - Single-link to LVDS Channel B tested.
  *   - 2x Single-link LVDS mode unsupported
  *     (should be easy to add by someone who has the HW)
  * - SN65DSI85
@@ -158,7 +160,7 @@ struct sn65dsi83 {
 	struct gpio_desc		*enable_gpio;
 	struct regulator		*vcc;
 	bool				lvds_dual_link;
-	bool				lvds_dual_link_even_odd_swap;
+	bool				lvds_channel_swap;
 	int				lvds_vod_swing_conf[2];
 	int				lvds_term_conf[2];
 	int				irq;
@@ -587,7 +589,7 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
 			REG_LVDS_VCOM_CHA_LVDS_VOD_SWING(ctx->lvds_vod_swing_conf[CHANNEL_A]) |
 			REG_LVDS_VCOM_CHB_LVDS_VOD_SWING(ctx->lvds_vod_swing_conf[CHANNEL_B]));
 	regmap_write(ctx->regmap, REG_LVDS_LANE,
-		     (ctx->lvds_dual_link_even_odd_swap ?
+		     (ctx->lvds_channel_swap ?
 		      REG_LVDS_LANE_EVEN_ODD_SWAP : 0) |
 		     (ctx->lvds_term_conf[CHANNEL_A] ?
 			  REG_LVDS_LANE_CHA_LVDS_TERM : 0) |
@@ -834,6 +836,7 @@ static int sn65dsi83_parse_dt(struct sn65dsi83 *ctx, enum sn65dsi83_model model)
 {
 	struct drm_bridge *panel_bridge;
 	struct device *dev = ctx->dev;
+	u32 panel_port = 2;
 	int ret;
 
 	ret = sn65dsi83_parse_lvds_endpoint(ctx, CHANNEL_A);
@@ -845,29 +848,38 @@ static int sn65dsi83_parse_dt(struct sn65dsi83 *ctx, enum sn65dsi83_model model)
 		return ret;
 
 	ctx->lvds_dual_link = false;
-	ctx->lvds_dual_link_even_odd_swap = false;
+	ctx->lvds_channel_swap = false;
 	if (model != MODEL_SN65DSI83) {
-		struct device_node *port2, *port3;
+		struct device_node *port0, *port1, *port2, *port3;
 		int dual_link;
 
+		port0 = of_graph_get_port_by_id(dev->of_node, 0);
+		port1 = of_graph_get_port_by_id(dev->of_node, 1);
 		port2 = of_graph_get_port_by_id(dev->of_node, 2);
 		port3 = of_graph_get_port_by_id(dev->of_node, 3);
 		dual_link = drm_of_lvds_get_dual_link_pixel_order(port2, port3);
-		of_node_put(port2);
-		of_node_put(port3);
 
 		if (dual_link == DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS) {
-			ctx->lvds_dual_link = true;
 			/* Odd pixels to LVDS Channel A, even pixels to B */
-			ctx->lvds_dual_link_even_odd_swap = false;
-		} else if (dual_link == DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS) {
 			ctx->lvds_dual_link = true;
+		} else if (dual_link == DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS) {
 			/* Even pixels to LVDS Channel A, odd pixels to B */
-			ctx->lvds_dual_link_even_odd_swap = true;
+			ctx->lvds_dual_link = true;
+			ctx->lvds_channel_swap = true;
+		} else if (port0 && !port1 && port2 && !port3) {
+			/* DSI Channel A to LVDS Channel A */
+		} else if (port0 && !port1 && !port2 && port3) {
+			/* DSI Channel A to LVDS Channel B */
+			ctx->lvds_channel_swap = true;
+			panel_port = 3;
 		}
+		of_node_put(port0);
+		of_node_put(port1);
+		of_node_put(port2);
+		of_node_put(port3);
 	}
 
-	panel_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 2, 0);
+	panel_bridge = devm_drm_of_get_bridge(dev, dev->of_node, panel_port, 0);
 	if (IS_ERR(panel_bridge))
 		return dev_err_probe(dev, PTR_ERR(panel_bridge), "Failed to get panel bridge\n");
 

---
base-commit: b4432656b36e5cc1d50a1f2dc15357543add530e
change-id: 20250430-sn65dsi83-channel-swap-f73afc78ace8

Best regards,
-- 
Esben Haabendal <esben@...nix.com>