[PATCH v4 0/2] drm/bridge: ti-sn65dsi83: Add reverse lvds lanes support

[PATCH v4 0/2] 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 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 (2):
  dt-bindings: display: sn65dsi83: Add output data-lanes
  drm/bridge: ti-sn65dsi83: Add reversed lvds lanes support

 .../bindings/display/bridge/ti,sn65dsi83.yaml | 52 +++++++++++++++++++
 drivers/gpu/drm/bridge/ti-sn65dsi83.c         | 50 ++++++++++++++++++
 2 files changed, 102 insertions(+)

-- 
2.47.3

[PATCH v4 1/2] dt-bindings: display: sn65dsi83: Add output data-lanes

[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 | 52 +++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
index e69b6343a8eb..2693c0273f9a 100644
--- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
@@ -86,10 +86,62 @@ 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
+                    description: |
+                      This is the default layout
+                  - items:
+                      - const: 4
+                      - const: 3
+                      - const: 2
+                      - const: 1
+                    description: |
+                      This is the reversed layout
+
       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
+                    description: |
+                      This is the default layout
+                  - items:
+                      - const: 4
+                      - const: 3
+                      - const: 2
+                      - const: 1
+                    description: |
+                      This is the reversed layout
+
     required:
       - port@0
       - port@2
-- 
2.47.3

Re: [PATCH v4 1/2] dt-bindings: display: sn65dsi83: Add output data-lanes

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 4 potential issue(s) to consider:
- [High] The inline `unevaluatedProperties: false` on `endpoint` blocks valid LVDS-specific properties inherited from `#/$defs/lvds-port`.
- [Medium] The `data-lanes` schema implicitly forces exactly 4 elements, breaking valid 3-lane LVDS configurations.
- [Low] Unnecessary duplication of the `data-lanes` schema block across `port@2` and `port@3`.
- [Low] Redundant `$ref` to `uint32-array` for a standard media property.
--

--- Patch [1]: [PATCH v4 1/2] dt-bindings: display: sn65dsi83: Add output data-lanes ---
commit 15be6ea27b74f8702a5daf407df624dc92403b9d
Author: Wojciech Dubowik <Wojciech.Dubowik@mt.com>

dt-bindings: display: sn65dsi83: Add output data-lanes

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.

> diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
> index e69b6343a8ebb..2693c0273f9ad 100644
> --- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml
> @@ -86,10 +86,62 @@ 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

[Severity: High]
Will this inline unevaluatedProperties block valid LVDS-specific properties
inherited from the shared lvds-port definition?

In JSON Schema 2019-09, unevaluatedProperties only considers properties
evaluated within its immediate schema object or its direct references. This
means it might incorrectly reject properties defined in
$defs/lvds-port/properties/endpoint.

> +
> +            properties:
> +              data-lanes:

[Severity: Low]
Could this entire data-lanes property definition be defined once centrally
inside $defs/lvds-port/properties/endpoint/properties instead of duplicating
it across both port@2 and port@3?

Placing it in the shared definition might also resolve the
unevaluatedProperties conflict.

> +                $ref: /schemas/types.yaml#/definitions/uint32-array

[Severity: Low]
Is this explicit type reference necessary?

The endpoint references /schemas/media/video-interfaces.yaml#, which already
enforces the uint32-array type for data-lanes globally.

> +                description: |
> +                  Array of physical LVDS data lane indexes
> +                oneOf:
> +                  - items:
> +                      - const: 1
> +                      - const: 2
> +                      - const: 3
> +                      - const: 4

[Severity: Medium]
Does this implicitly force exactly 4 elements and reject valid 3-lane LVDS
configurations?

Providing a YAML array for items without specifying minItems implicitly sets
both minItems and maxItems to the array's length (4). Since the SN65DSI83
hardware supports 18-bpp (3-lane) configurations, device trees using
data-lanes = <1 2 3> might fail validation.

> +                    description: |
> +                      This is the default layout
> +                  - items:
> +                      - const: 4
> +                      - const: 3
> +                      - const: 2
> +                      - const: 1
> +                    description: |
> +                      This is the reversed layout
> +

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260713082622.52985-1-wojciech.dubowik@mt.com?part=1

[PATCH v4 2/2] 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, 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 | 50 +++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index 42b451432bbb..4945d4c960c4 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 {
+	NORMAL_LANE_MAPPING,
+	REVERSE_LANE_MAPPING,
+};
+
+#define DATA_LANES_COUNT	4
+
+static const int supported_data_lane_mapping[][DATA_LANES_COUNT] = {
+	[NORMAL_LANE_MAPPING] = { 1, 2, 3, 4 },
+	[REVERSE_LANE_MAPPING] = { 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] ?
@@ -832,10 +849,12 @@ 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 = 0;
 	int ret_data;
 	int ret_clock;
+	int i, j;
 
 	if (channel == CHANNEL_A)
 		endpoint_reg = 2;
@@ -854,6 +873,37 @@ static int sn65dsi83_parse_lvds_endpoint(struct sn65dsi83 *ctx, int channel)
 		goto exit;
 	}
 
+	ret_data = of_property_read_u32_array(endpoint, "data-lanes", data_lanes,
+			ARRAY_SIZE(data_lanes));
+	if (ret_data != 0 && ret_data != -EINVAL) {
+		ret = ret_data;
+		goto exit;
+	}
+
+	if (!ret_data) {
+		for (i = 0; i < ARRAY_SIZE(supported_data_lane_mapping); i++) {
+			for (j = 0; j < DATA_LANES_COUNT; j++) {
+				if (data_lanes[j] != supported_data_lane_mapping[i][j])
+					break;
+			}
+
+			if (j == DATA_LANES_COUNT)
+				break;
+		}
+
+		switch (i) {
+		case NORMAL_LANE_MAPPING:
+			break;
+		case REVERSE_LANE_MAPPING:
+			ctx->lvds_reverse_lanes_conf[channel] = true;
+			break;
+		default:
+			dev_err(dev, "invalid data lanes mapping\n");
+			ret = -EINVAL;
+			goto exit;
+		}
+	}
+
 	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