[PATCH v5 0/3] drm/bridge: ti-sn65dsi83: Add reverse lvds lanes support

[PATCH v5 0/3] drm/bridge: ti-sn65dsi83: Add reverse lvds lanes support

[Wojciech Dubowik]

From: Wojciech Dubowik <Wojciech.Dubowik@mt.com>

Add support for reversed lvds output lanes. With an optional
data-lanes property one can support default layout <1 2 3 4>
or reversed layout <4 3 2 1>. The property is optional and when
not set it keeps the default output layout.

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@mt.com>
---
Changes in v5:
- Add an extra patch to simplify error handling in lvds DT parsing
  suggested by Luca
- Fix formatting and description in dt-bindings
- Make naming consistent for lane mappings constants
- Simplify parsing of data-lanes
Changes in v4:
- Fix data-lanes bindings to be under endpoint subnode and not in
  the node itself, discovered by shashiko-reviews
Changes in v3:
- Add optional data-lanes bindings for output nodes
Changes in v2:
- Parse existing data-lanes property instead of ading new DT
  bindings
---
Wojciech Dubowik (3):
  drm/bridge: ti-sn65dsi83: Simplify error condition logic
  dt-bindings: display: sn65dsi83: Add output data-lanes property
  drm/bridge: ti-sn65dsi83: Add reversed lvds lanes support

 .../bindings/display/bridge/ti,sn65dsi83.yaml | 44 ++++++++++++
 drivers/gpu/drm/bridge/ti-sn65dsi83.c         | 72 +++++++++++--------
 2 files changed, 87 insertions(+), 29 deletions(-)

-- 
2.47.3

[PATCH v5 1/3] drm/bridge: ti-sn65dsi83: Simplify error condition logic

[Wojciech Dubowik]

From: Wojciech Dubowik <Wojciech.Dubowik@mt.com>

Simplify error condition logic in lvds device tree property parsing. It
makes it easier to add extra properties without handling complex goto
entries.

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@mt.com>
---
 drivers/gpu/drm/bridge/ti-sn65dsi83.c | 43 ++++++++-------------------
 1 file changed, 13 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index 42b451432bbb..f8a786953526 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -825,48 +825,35 @@ static int sn65dsi83_select_lvds_vod_swing(struct device *dev,
 static int sn65dsi83_parse_lvds_endpoint(struct sn65dsi83 *ctx, int channel)
 {
 	struct device *dev = ctx->dev;
-	struct device_node *endpoint;
-	int endpoint_reg;
+	int endpoint_reg = (channel == CHANNEL_A) ? 2 : 3;
+	struct device_node *endpoint __free(device_node) =
+		of_graph_get_endpoint_by_regs(dev->of_node, endpoint_reg, -1);
 	/* Set so the property can be freely selected if not defined */
 	u32 lvds_vod_swing_data[2] = { 0, 1000000 };
 	u32 lvds_vod_swing_clk[2] = { 0, 1000000 };
 	/* Set default near end terminataion to 200 Ohm */
 	u32 lvds_term = 200;
 	int lvds_vod_swing_conf;
-	int ret = 0;
 	int ret_data;
 	int ret_clock;
 
-	if (channel == CHANNEL_A)
-		endpoint_reg = 2;
-	else
-		endpoint_reg = 3;
-
-	endpoint = of_graph_get_endpoint_by_regs(dev->of_node, endpoint_reg, -1);
-
 	of_property_read_u32(endpoint, "ti,lvds-termination-ohms", &lvds_term);
 	if (lvds_term == 100)
 		ctx->lvds_term_conf[channel] = OHM_100;
 	else if (lvds_term == 200)
 		ctx->lvds_term_conf[channel] = OHM_200;
-	else {
-		ret = -EINVAL;
-		goto exit;
-	}
+	else
+		return -EINVAL;
 
 	ret_data = of_property_read_u32_array(endpoint, "ti,lvds-vod-swing-data-microvolt",
 					lvds_vod_swing_data, ARRAY_SIZE(lvds_vod_swing_data));
-	if (ret_data != 0 && ret_data != -EINVAL) {
-		ret = ret_data;
-		goto exit;
-	}
+	if (ret_data != 0 && ret_data != -EINVAL)
+		return ret_data;
 
 	ret_clock = of_property_read_u32_array(endpoint, "ti,lvds-vod-swing-clock-microvolt",
 					lvds_vod_swing_clk, ARRAY_SIZE(lvds_vod_swing_clk));
-	if (ret_clock != 0 && ret_clock != -EINVAL) {
-		ret = ret_clock;
-		goto exit;
-	}
+	if (ret_clock != 0 && ret_clock != -EINVAL)
+		return ret_clock;
 
 	/* Use default value if both properties are NOT defined. */
 	if (ret_data == -EINVAL && ret_clock == -EINVAL)
@@ -876,17 +863,13 @@ static int sn65dsi83_parse_lvds_endpoint(struct sn65dsi83 *ctx, int channel)
 	if (!ret_data || !ret_clock) {
 		lvds_vod_swing_conf = sn65dsi83_select_lvds_vod_swing(dev, lvds_vod_swing_data,
 						lvds_vod_swing_clk, ctx->lvds_term_conf[channel]);
-		if (lvds_vod_swing_conf < 0) {
-			ret = lvds_vod_swing_conf;
-			goto exit;
-		}
+		if (lvds_vod_swing_conf < 0)
+			return lvds_vod_swing_conf;
 	}
 
 	ctx->lvds_vod_swing_conf[channel] = lvds_vod_swing_conf;
-	ret = 0;
-exit:
-	of_node_put(endpoint);
-	return ret;
+
+	return 0;
 }
 
 static int sn65dsi83_parse_dt(struct sn65dsi83 *ctx, enum sn65dsi83_model model)
-- 
2.47.3

[PATCH v5 2/3] dt-bindings: display: sn65dsi83: Add output data-lanes property

[Wojciech Dubowik]

From: Wojciech Dubowik <Wojciech.Dubowik@mt.com>

Add an optional output lvds data lanes property with two allowed values.
The array <1 2 3 4> for standard layout and <4 3 2 1> for reversed lvds
output lanes. The latter informs the driver that reverse lvds config
option has to be set in config register for the respective output channel.

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@mt.com>
---
 .../bindings/display/bridge/ti,sn65dsi83.yaml | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
index e69b6343a8eb..4000bf0b1370 100644
--- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
@@ -86,10 +86,54 @@ properties:
         description: Video port for LVDS Channel-A output (panel or bridge).
         $ref: '#/$defs/lvds-port'
 
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+            properties:
+              data-lanes:
+                $ref: /schemas/types.yaml#/definitions/uint32-array
+                description:
+                  Array of physical LVDS data lane indexes
+                oneOf:
+                  - items:
+                      - const: 1
+                      - const: 2
+                      - const: 3
+                      - const: 4
+                  - items:
+                      - const: 4
+                      - const: 3
+                      - const: 2
+                      - const: 1
+
       port@3:
         description: Video port for LVDS Channel-B output (panel or bridge).
         $ref: '#/$defs/lvds-port'
 
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+            properties:
+              data-lanes:
+                $ref: /schemas/types.yaml#/definitions/uint32-array
+                description:
+                  Array of physical LVDS data lane indexes
+                oneOf:
+                  - items:
+                      - const: 1
+                      - const: 2
+                      - const: 3
+                      - const: 4
+                  - items:
+                      - const: 4
+                      - const: 3
+                      - const: 2
+                      - const: 1
+
     required:
       - port@0
       - port@2
-- 
2.47.3

[PATCH v5 3/3] drm/bridge: ti-sn65dsi83: Add reversed lvds lanes support

[Wojciech Dubowik]

From: Wojciech Dubowik <Wojciech.Dubowik@mt.com>

The chip supports output lvds lanes in two orders, the default <1 2 3 4>
and <4 3 2 1>. Add parsing of an optional output lvds data-lanes property
so we can inform chip that the lanes have been reversed.

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@mt.com>
---
 drivers/gpu/drm/bridge/ti-sn65dsi83.c | 31 +++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index f8a786953526..df44df2e872a 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -148,6 +148,18 @@ enum sn65dsi83_lvds_term {
 	OHM_200
 };
 
+enum {
+	LANE_MAPPING_NORMAL,
+	LANE_MAPPING_REVERSE,
+};
+
+#define DATA_LANES_COUNT	4
+
+static const u32 supported_data_lane_mapping[][DATA_LANES_COUNT] = {
+	[LANE_MAPPING_NORMAL] = { 1, 2, 3, 4 },
+	[LANE_MAPPING_REVERSE] = { 4, 3, 2, 1},
+};
+
 enum sn65dsi83_model {
 	MODEL_SN65DSI83,
 	MODEL_SN65DSI84,
@@ -163,6 +175,7 @@ struct sn65dsi83 {
 	struct regulator		*vcc;
 	bool				lvds_dual_link;
 	bool				lvds_dual_link_even_odd_swap;
+	bool				lvds_reverse_lanes_conf[2];
 	int				lvds_vod_swing_conf[2];
 	int				lvds_term_conf[2];
 	int				irq;
@@ -644,6 +657,10 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
 	regmap_write(ctx->regmap, REG_LVDS_LANE,
 		     (ctx->lvds_dual_link_even_odd_swap ?
 		      REG_LVDS_LANE_EVEN_ODD_SWAP : 0) |
+		     (ctx->lvds_reverse_lanes_conf[CHANNEL_A] ?
+		      REG_LVDS_LANE_CHA_REVERSE_LVDS : 0) |
+		     (ctx->lvds_reverse_lanes_conf[CHANNEL_B] ?
+		      REG_LVDS_LANE_CHB_REVERSE_LVDS : 0) |
 		     (ctx->lvds_term_conf[CHANNEL_A] ?
 			  REG_LVDS_LANE_CHA_LVDS_TERM : 0) |
 		     (ctx->lvds_term_conf[CHANNEL_B] ?
@@ -833,6 +850,7 @@ static int sn65dsi83_parse_lvds_endpoint(struct sn65dsi83 *ctx, int channel)
 	u32 lvds_vod_swing_clk[2] = { 0, 1000000 };
 	/* Set default near end terminataion to 200 Ohm */
 	u32 lvds_term = 200;
+	u32 data_lanes[DATA_LANES_COUNT];
 	int lvds_vod_swing_conf;
 	int ret_data;
 	int ret_clock;
@@ -845,6 +863,19 @@ static int sn65dsi83_parse_lvds_endpoint(struct sn65dsi83 *ctx, int channel)
 	else
 		return -EINVAL;
 
+	ret_data = of_property_read_u32_array(endpoint, "data-lanes", data_lanes,
+			ARRAY_SIZE(data_lanes));
+	if (!ret_data) {
+		if (memcmp(data_lanes,
+				supported_data_lane_mapping[LANE_MAPPING_REVERSE],
+				ARRAY_SIZE(data_lanes)) == 0)
+			ctx->lvds_reverse_lanes_conf[channel] = true;
+		else if (memcmp(data_lanes,
+			   supported_data_lane_mapping[LANE_MAPPING_NORMAL],
+			   ARRAY_SIZE(data_lanes)) != 0)
+			return dev_err_probe(dev, -EINVAL, "invalid data lanes mapping\n");
+	}
+
 	ret_data = of_property_read_u32_array(endpoint, "ti,lvds-vod-swing-data-microvolt",
 					lvds_vod_swing_data, ARRAY_SIZE(lvds_vod_swing_data));
 	if (ret_data != 0 && ret_data != -EINVAL)
-- 
2.47.3

Re: [PATCH v5 1/3] drm/bridge: ti-sn65dsi83: Simplify error condition logic

[Luca Ceresoli]

On Fri, 17 Jul 2026 13:49:59 +0200, Wojciech Dubowik <wojciech.dubowik@mt.com> wrote:
> Simplify error condition logic in lvds device tree property parsing. It
> makes it easier to add extra properties without handling complex goto
> entries.

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH v5 3/3] drm/bridge: ti-sn65dsi83: Add reversed lvds lanes support

[Luca Ceresoli]

On Fri, 17 Jul 2026 13:50:01 +0200, Wojciech Dubowik <wojciech.dubowik@mt.com> wrote:

Hello,

>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> index f8a786953526..df44df2e872a 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> @@ -845,6 +863,19 @@ static int sn65dsi83_parse_lvds_endpoint(struct sn65dsi83 *ctx, int channel)
>  	else
>  		return -EINVAL;
>  
> +	ret_data = of_property_read_u32_array(endpoint, "data-lanes", data_lanes,
> +			ARRAY_SIZE(data_lanes));
> +	if (!ret_data) {
> +		if (memcmp(data_lanes,
> +				supported_data_lane_mapping[LANE_MAPPING_REVERSE],
> +				ARRAY_SIZE(data_lanes)) == 0)

Did you have a look at this sashiko report? It seems valid:
 | sashiko-bot@kernel.org <sashiko-bot@kernel.org>:
 |
 | [Severity: Medium]
 | Does this code compare the entire array? memcmp() expects the length in
 | bytes, but ARRAY_SIZE(data_lanes) evaluates to 4 (the number of elements).
 |
 | Because data_lanes is an array of u32, checking only 4 bytes means only
 | the first element is compared. Should this be using sizeof(data_lanes)
 | instead?
 |
 | via: https://patch.msgid.link/20260717115630.C58A61F000E9@smtp.kernel.org

> +			ctx->lvds_reverse_lanes_conf[channel] = true;
> +		else if (memcmp(data_lanes,
> +			   supported_data_lane_mapping[LANE_MAPPING_NORMAL],
> +			   ARRAY_SIZE(data_lanes)) != 0)

Same here.

Otherwise looks good.

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com