linux-kernel - [PATCH 2/3] drm/bridge: lt9611: Add support for DSI port B input

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Message-Id: <20260127-rubikpi-next-20260116-v1-2-0286c75150c5@thundersoft.com>
Date: Tue, 27 Jan 2026 14:58:12 +0800
From: Hongyang Zhao <hongyang.zhao@...ndersoft.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>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>, 
 Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konradybcio@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 Hongyang Zhao <hongyang.zhao@...ndersoft.com>, 
 Roger Shimizu <rosh@...ian.org>
Subject: [PATCH 2/3] drm/bridge: lt9611: Add support for DSI port B input

The LT9611 has two DSI input ports. The driver currently hardcodes
Port A or Port A+B, but some boards connect DSI to Port B only.

Add device tree property "lontium,dsi-port-b" to select Port B as the
DSI input source. When set, configure port swap (0x8303 bit 6) and
byte_clk source (0x8250 bit 3:2) for Port B.

Signed-off-by: Hongyang Zhao <hongyang.zhao@...ndersoft.com>
Reviewed-by: Roger Shimizu <rosh@...ian.org>
---
 drivers/gpu/drm/bridge/lontium-lt9611.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
index a2d032ee4744..178f056c9e85 100644
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -47,6 +47,7 @@ struct lt9611 {
 	struct mipi_dsi_device *dsi1;
 
 	bool ac_mode;
+	bool dsi_port_b;
 
 	struct gpio_desc *reset_gpio;
 	struct gpio_desc *enable_gpio;
@@ -116,6 +117,7 @@ static int lt9611_mipi_input_digital(struct lt9611 *lt9611,
 		{ 0x830a, 0x00 },
 		{ 0x824f, 0x80 },
 		{ 0x8250, 0x10 },
+		{ 0x8303, 0x00 },
 		{ 0x8302, 0x0a },
 		{ 0x8306, 0x0a },
 	};
@@ -123,6 +125,16 @@ static int lt9611_mipi_input_digital(struct lt9611 *lt9611,
 	if (lt9611->dsi1_node)
 		reg_cfg[1].def = 0x03;
 
+	/*
+	 * Select DSI input port:
+	 * - 0x8303 bit 6: port swap (0=PortA, 1=PortB)
+	 * - 0x8250 bit 3:2: byte_clk source (00=PortA, 01=PortB)
+	 */
+	if (lt9611->dsi_port_b) {
+		reg_cfg[3].def = 0x14;
+		reg_cfg[4].def = 0x40;
+	}
+
 	return regmap_multi_reg_write(lt9611->regmap, reg_cfg, ARRAY_SIZE(reg_cfg));
 }
 
@@ -1024,6 +1036,8 @@ static int lt9611_parse_dt(struct device *dev,
 
 	lt9611->ac_mode = of_property_read_bool(dev->of_node, "lt,ac-mode");
 
+	lt9611->dsi_port_b = of_property_read_bool(dev->of_node, "lontium,dsi-port-b");
+
 	return drm_of_find_panel_or_bridge(dev->of_node, 2, -1, NULL, &lt9611->next_bridge);
 }
 

-- 
2.43.0