[PATCH v2 0/3] Add VGA support for Apalis iMX6

[PATCH v2 0/3] Add VGA support for Apalis iMX6

[Leonardo Costa]

This series adds a device tree overlay that enables the VGA output on Apalis
iMX6, which is driven from a parallel RGB interface passing through a
non-programmable video DAC.

The video DAC is a simple resistor network gated by an active-low
data-enable signal. For the bridge to work properly, this series also
changes the following in the dt-bindings and simple-bridge driver:

- dt-bindings: Add the existing data-enable-active property from
  video-interfaces.yaml to the simple-bridge binding. The property is
  read from the bridge's input endpoint. This allows a dumb-vga-dac to
  specify a data-enable signal polarity.

- simple-bridge: Read the data-enable-active property and fill out the
  bridge's input bus flags accordingly. The property is ignored if the
  bridge already has its own timings struct defined, to not interfere
  with its existing settings.

This change depends on another patch, and should be applied after it:

- https://lore.kernel.org/all/20261002-v1-simple-bridge-atomic-check-v1-1-ef5d8332b078@toradex.com/T/#u

  Adds the atomic_check function to the simple-bridge driver, which
  allows the data-enable bus flag to be propagated through the DRM
  pipeline. This is necessary for the VGA to work correctly on the
  Apalis iMX6.

Changes in v2:
  - Introduce the data-enable-active property.
  - Describe the VGA bridge on the Apalis iMX6 as a dumb-vga-dac using
    the data-enable-active property to specify the DE signal polarity,
    instead of using a dedicated compatible.
  - Link to v1: https://lore.kernel.org/all/as-heYw7PKLPm3yH@SMW015318/T/#u

Signed-off-by: Leonardo Costa <leonardo.costa@toradex.com>
---
Leonardo Costa (3):
      dt-bindings: display: bridge: simple: Add data-enable-active to dumb-vga-dac
      drm/bridge: simple-bridge: Support data-enable-active endpoint property
      ARM: dts: imx6q-apalis: Add VGA overlay

 .../bindings/display/bridge/simple-bridge.yaml     | 28 +++++++-
 arch/arm/boot/dts/nxp/imx/Makefile                 | 21 ++++++
 .../boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso    | 80 ++++++++++++++++++++++
 drivers/gpu/drm/bridge/simple-bridge.c             | 21 +++++-
 4 files changed, 148 insertions(+), 2 deletions(-)
---
base-commit: f33c2a109da4a527ed3103acb649a88e88cf368c
change-id: 20261014-v2-apalis-imx6-enable-vga-450f5777a476

Best regards,
-- 
Leonardo Costa <leonardo.costa@toradex.com>

[PATCH v2 1/3] dt-bindings: display: bridge: simple: Add data-enable-active to dumb-vga-dac

[Leonardo Costa]

From: Leonardo Costa <leonardo.costa@toradex.com>

Some simple VGA DACs may include a data-enable input that must be driven
at a specific polarity. Add the data-enable-active property from
video-interfaces to the input endpoint to describe that polarity.

Signed-off-by: Leonardo Costa <leonardo.costa@toradex.com>
---
 .../bindings/display/bridge/simple-bridge.yaml     | 28 +++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml b/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml
index 7636c24906ba..b1b23d41245d 100644
--- a/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml
@@ -43,9 +43,18 @@ properties:
 
     properties:
       port@0:
-        $ref: /schemas/graph.yaml#/properties/port
+        $ref: /schemas/graph.yaml#/$defs/port-base
+        unevaluatedProperties: false
         description: The bridge input
 
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml
+            unevaluatedProperties: false
+
+            properties:
+              data-enable-active: true
+
       port@1:
         $ref: /schemas/graph.yaml#/properties/port
         description: The bridge output
@@ -65,6 +74,23 @@ required:
   - compatible
   - ports
 
+allOf:
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              const: dumb-vga-dac
+    then:
+      properties:
+        ports:
+          properties:
+            port@0:
+              properties:
+                endpoint:
+                  properties:
+                    data-enable-active: false
+
 additionalProperties: false
 
 examples:

-- 
2.43.0

Re: [PATCH v2 1/3] dt-bindings: display: bridge: simple: Add data-enable-active to dumb-vga-dac

[Frank Li]

On Mon, Oct 19, 2026 at 07:17:14AM -0300, Leonardo Costa wrote:
> From: Leonardo Costa <leonardo.costa@toradex.com>
>
> Some simple VGA DACs may include a data-enable input that must be driven
> at a specific polarity. Add the data-enable-active property from
> video-interfaces to the input endpoint to describe that polarity.
>
> Signed-off-by: Leonardo Costa <leonardo.costa@toradex.com>
> ---
>  .../bindings/display/bridge/simple-bridge.yaml     | 28 +++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml b/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml
> index 7636c24906ba..b1b23d41245d 100644
> --- a/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/simple-bridge.yaml
> @@ -43,9 +43,18 @@ properties:
>
>      properties:
>        port@0:
> -        $ref: /schemas/graph.yaml#/properties/port
> +        $ref: /schemas/graph.yaml#/$defs/port-base
> +        unevaluatedProperties: false
>          description: The bridge input
>
> +        properties:
> +          endpoint:
> +            $ref: /schemas/media/video-interfaces.yaml
> +            unevaluatedProperties: false
> +
> +            properties:
> +              data-enable-active: true
> +

suppose needn't it because unevaluatedProperties: false, which allow all
property in video-interfaces.yaml.

If you only want to enable one property, should be
additionalProperties: false

but I think unevaluatedProperties: false make sense and needn't below if
branch.

Frank

>        port@1:
>          $ref: /schemas/graph.yaml#/properties/port
>          description: The bridge output
> @@ -65,6 +74,23 @@ required:
>    - compatible
>    - ports
>
> +allOf:
> +  - if:
> +      not:
> +        properties:
> +          compatible:
> +            contains:
> +              const: dumb-vga-dac
> +    then:
> +      properties:
> +        ports:
> +          properties:
> +            port@0:
> +              properties:
> +                endpoint:
> +                  properties:
> +                    data-enable-active: false
> +
>  additionalProperties: false
>
>  examples:
>
> --
> 2.43.0
>
>

[PATCH v2 2/3] drm/bridge: simple-bridge: Support data-enable-active endpoint property

[Leonardo Costa]

From: Leonardo Costa <leonardo.costa@toradex.com>

Some simple bridges, such as a resistor ladder DAC, may include a
data-enable input that must be driven at a specific polarity.

Read the data-enable-active property from the input endpoint and fill
the bridge's input bus flags accordingly, so the upstream encoder drives
DE with the required polarity. The property is applied only if the
bridge doesn't provide its own timings struct.

Signed-off-by: Leonardo Costa <leonardo.costa@toradex.com>
---
 drivers/gpu/drm/bridge/simple-bridge.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
index 848c2df2a276..c5301295658a 100644
--- a/drivers/gpu/drm/bridge/simple-bridge.c
+++ b/drivers/gpu/drm/bridge/simple-bridge.c
@@ -183,6 +183,9 @@ static int simple_bridge_probe(struct platform_device *pdev)
 {
 	struct simple_bridge *sbridge;
 	struct device_node *remote;
+	struct device_node *ep;
+	bool de_present;
+	u32 de;
 
 	sbridge = devm_drm_bridge_alloc(&pdev->dev, struct simple_bridge,
 					bridge, &simple_bridge_bridge_funcs);
@@ -220,10 +223,26 @@ static int simple_bridge_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, PTR_ERR(sbridge->enable),
 				     "Unable to retrieve enable GPIO\n");
 
-	/* Register the bridge. */
 	sbridge->bridge.of_node = pdev->dev.of_node;
 	sbridge->bridge.timings = sbridge->info->timings;
 
+	ep = of_graph_get_endpoint_by_regs(pdev->dev.of_node, 0, -1);
+	de_present = !of_property_read_u32(ep, "data-enable-active", &de);
+	of_node_put(ep);
+
+	if (de_present && !sbridge->bridge.timings) {
+		struct drm_bridge_timings *timings;
+
+		timings = devm_kzalloc(&pdev->dev, sizeof(*timings), GFP_KERNEL);
+		if (!timings)
+			return -ENOMEM;
+
+		timings->input_bus_flags = de ? DRM_BUS_FLAG_DE_HIGH :
+						DRM_BUS_FLAG_DE_LOW;
+		sbridge->bridge.timings = timings;
+	}
+
+	/* Register the bridge. */
 	return devm_drm_bridge_add(&pdev->dev, &sbridge->bridge);
 }
 

-- 
2.43.0

Re: [PATCH v2 2/3] drm/bridge: simple-bridge: Support data-enable-active endpoint property

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] drm/bridge: simple-bridge: missing atomic_check() to propagate DE bus flags
- [Medium] drm/bridge: simple-bridge: timings devm_kzalloc() lifetime mismatch
--

commit 17d03fa8dcd99e5bb3af7da622344c856ca2c887
Author: Leonardo Costa <leonardo.costa@toradex.com>

drm/bridge: simple-bridge: Support data-enable-active endpoint property

This commit reads the data-enable-active property from the input endpoint in
simple_bridge_probe() and allocates a drm_bridge_timings structure to set
DRM_BUS_FLAG_DE_HIGH or DRM_BUS_FLAG_DE_LOW in input_bus_flags when the bridge
does not already define its own timings.

> diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
> index 3fba7002322e9..393228bed6e28 100644
> --- a/drivers/gpu/drm/bridge/simple-bridge.c
> +++ b/drivers/gpu/drm/bridge/simple-bridge.c
> @@ -171,6 +171,9 @@ static int simple_bridge_probe(struct platform_device *pdev)
>  {
>  	struct simple_bridge *sbridge;
>  	struct device_node *remote;
> +	struct device_node *ep;
> +	bool de_present;
> +	u32 de;
>  
>  	sbridge = devm_drm_bridge_alloc(&pdev->dev, struct simple_bridge,
>  					bridge, &simple_bridge_bridge_funcs);
> @@ -208,10 +211,26 @@ static int simple_bridge_probe(struct platform_device *pdev)
>  		return dev_err_probe(&pdev->dev, PTR_ERR(sbridge->enable),
>  				     "Unable to retrieve enable GPIO\n");
>  
> -	/* Register the bridge. */
>  	sbridge->bridge.of_node = pdev->dev.of_node;
>  	sbridge->bridge.timings = sbridge->info->timings;
>  
> +	ep = of_graph_get_endpoint_by_regs(pdev->dev.of_node, 0, -1);
> +	de_present = !of_property_read_u32(ep, "data-enable-active", &de);
> +	of_node_put(ep);
> +
> +	if (de_present && !sbridge->bridge.timings) {
> +		struct drm_bridge_timings *timings;
> +
> +		timings = devm_kzalloc(&pdev->dev, sizeof(*timings), GFP_KERNEL);
> +		if (!timings)
> +			return -ENOMEM;

[Severity: Medium]
Can allocating timings with devm_kzalloc() in simple_bridge_probe() cause a
lifetime mismatch with sbridge->bridge?

sbridge is allocated via devm_drm_bridge_alloc(), which manages the container's
lifetime through sbridge->bridge.refcount and only frees it in
__drm_bridge_free() after all drm_bridge references are dropped:

drivers/gpu/drm/drm_bridge.c:__drm_bridge_free()
	if (bridge->funcs->destroy)
		bridge->funcs->destroy(bridge);

	drm_bridge_put(bridge->next_bridge);

	kfree(bridge->container);

If pdev is unbound while an upstream bridge or encoder still holds a reference
to sbridge->bridge, devres_release_all() will free timings immediately, leaving
sbridge->bridge.timings as a dangling pointer that can be dereferenced by
upstream drivers (for example, in imx8mp_hdmi_pvi_bridge_enable()).

Would embedding struct drm_bridge_timings inside struct simple_bridge (as done
in lvds-codec.c and ti-tfp410.c), or pointing to static const
drm_bridge_timings instances for DRM_BUS_FLAG_DE_HIGH and DRM_BUS_FLAG_DE_LOW,
avoid this lifetime mismatch?

> +
> +		timings->input_bus_flags = de ? DRM_BUS_FLAG_DE_HIGH :
> +						DRM_BUS_FLAG_DE_LOW;
> +		sbridge->bridge.timings = timings;
> +	}

[Severity: High]
Will setting only sbridge->bridge.timings->input_bus_flags actually propagate
the DE polarity to upstream atomic encoders and bridges?

simple_bridge_bridge_funcs registers atomic state callbacks without an
.atomic_check callback:

drivers/gpu/drm/bridge/simple-bridge.c:
static const struct drm_bridge_funcs simple_bridge_bridge_funcs = {
	.atomic_create_state = drm_atomic_helper_bridge_create_state,
	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
	.attach		= simple_bridge_attach,
	.atomic_enable = simple_bridge_enable,
	.atomic_disable = simple_bridge_disable,
};

During an atomic modeset, drm_atomic_bridge_chain_check() calls
drm_atomic_bridge_propagate_bus_flags(), which overwrites
bridge_state->input_bus_cfg.flags with output_flags from the downstream bridge
or connector (0 for a VGA connector) and never checks
bridge->timings->input_bus_flags:

drivers/gpu/drm/drm_bridge.c:drm_atomic_bridge_propagate_bus_flags()
	bridge_state->output_bus_cfg.flags = output_flags;
	...
	bridge_state->input_bus_cfg.flags = output_flags;

Because simple-bridge has a valid drm_bridge_state, upstream bridges and atomic
encoders such as imx_pd_bridge_atomic_check() in
drivers/gpu/drm/imx/ipuv3/parallel-display.c read
next_bridge_state->input_bus_cfg.flags instead of
next_bridge->timings->input_bus_flags:

drivers/gpu/drm/imx/ipuv3/parallel-display.c:imx_pd_bridge_atomic_check()
	if (next_bridge_state)
		bus_flags = next_bridge_state->input_bus_cfg.flags;
	else
		bus_flags = di->bus_flags;

As a result, bus_flags remains 0 instead of DRM_BUS_FLAG_DE_LOW or
DRM_BUS_FLAG_DE_HIGH.

Should simple_bridge_bridge_funcs implement an .atomic_check callback that
copies sbridge->bridge.timings->input_bus_flags into
bridge_state->input_bus_cfg.flags (similar to tfp410_atomic_check() in
drivers/gpu/drm/bridge/ti-tfp410.c)?

> +
> +	/* Register the bridge. */
>  	return devm_drm_bridge_add(&pdev->dev, &sbridge->bridge);
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261019-v2-apalis-imx6-enable-vga-v2-0-ef6a3a780472@toradex.com?part=2

Re: [PATCH v2 2/3] drm/bridge: simple-bridge: Support data-enable-active endpoint property

[Frank Li]

On Mon, Oct 19, 2026 at 07:17:15AM -0300, Leonardo Costa wrote:
> From: Leonardo Costa <leonardo.costa@toradex.com>
>
> Some simple bridges, such as a resistor ladder DAC, may include a
> data-enable input that must be driven at a specific polarity.
>
> Read the data-enable-active property from the input endpoint and fill
> the bridge's input bus flags accordingly, so the upstream encoder drives
> DE with the required polarity. The property is applied only if the
> bridge doesn't provide its own timings struct.
>
> Signed-off-by: Leonardo Costa <leonardo.costa@toradex.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

>  drivers/gpu/drm/bridge/simple-bridge.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
> index 848c2df2a276..c5301295658a 100644
> --- a/drivers/gpu/drm/bridge/simple-bridge.c
> +++ b/drivers/gpu/drm/bridge/simple-bridge.c
> @@ -183,6 +183,9 @@ static int simple_bridge_probe(struct platform_device *pdev)
>  {
>  	struct simple_bridge *sbridge;
>  	struct device_node *remote;
> +	struct device_node *ep;
> +	bool de_present;
> +	u32 de;
>
>  	sbridge = devm_drm_bridge_alloc(&pdev->dev, struct simple_bridge,
>  					bridge, &simple_bridge_bridge_funcs);
> @@ -220,10 +223,26 @@ static int simple_bridge_probe(struct platform_device *pdev)
>  		return dev_err_probe(&pdev->dev, PTR_ERR(sbridge->enable),
>  				     "Unable to retrieve enable GPIO\n");
>
> -	/* Register the bridge. */
>  	sbridge->bridge.of_node = pdev->dev.of_node;
>  	sbridge->bridge.timings = sbridge->info->timings;
>
> +	ep = of_graph_get_endpoint_by_regs(pdev->dev.of_node, 0, -1);
> +	de_present = !of_property_read_u32(ep, "data-enable-active", &de);
> +	of_node_put(ep);
> +
> +	if (de_present && !sbridge->bridge.timings) {
> +		struct drm_bridge_timings *timings;
> +
> +		timings = devm_kzalloc(&pdev->dev, sizeof(*timings), GFP_KERNEL);
> +		if (!timings)
> +			return -ENOMEM;
> +
> +		timings->input_bus_flags = de ? DRM_BUS_FLAG_DE_HIGH :
> +						DRM_BUS_FLAG_DE_LOW;
> +		sbridge->bridge.timings = timings;
> +	}
> +
> +	/* Register the bridge. */
>  	return devm_drm_bridge_add(&pdev->dev, &sbridge->bridge);
>  }
>
>
> --
> 2.43.0
>
>

[PATCH v2 3/3] ARM: dts: imx6q-apalis: Add VGA overlay

[Leonardo Costa]

From: Leonardo Costa <leonardo.costa@toradex.com>

Add a device tree overlay for the VGA output available on the Apalis
Evaluation Board, which is driven from a parallel RGB interface passing
through a non-programmable video DAC to a VGA connector, without VESA
DDC I2C signals.

The non-programmable video DAC consists of a simple resistor ladder that
converts the digital 16-bit RGB signal to VGA. The VGA output is gated by
an active-low data-enable signal.

The overlay is also combined with the various Apalis Evaluation Board
device trees to provide ready-to-use DTBs.

Signed-off-by: Leonardo Costa <leonardo.costa@toradex.com>
---
 arch/arm/boot/dts/nxp/imx/Makefile                 | 21 ++++++
 .../boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso    | 80 ++++++++++++++++++++++
 2 files changed, 101 insertions(+)

diff --git a/arch/arm/boot/dts/nxp/imx/Makefile b/arch/arm/boot/dts/nxp/imx/Makefile
index b5fad2ba764c..9c218260fdcb 100644
--- a/arch/arm/boot/dts/nxp/imx/Makefile
+++ b/arch/arm/boot/dts/nxp/imx/Makefile
@@ -60,6 +60,22 @@ dtb-$(CONFIG_SOC_IMX53) += \
 imx53-qsb-hdmi-dtbs := imx53-qsb.dtb imx53-qsb-hdmi.dtbo
 imx53-qsrb-hdmi-dtbs := imx53-qsrb.dtb imx53-qsb-hdmi.dtbo
 
+imx6q-apalis-eval-v1.2-vga-dtbs := \
+	imx6q-apalis-eval-v1.2.dtb \
+	imx6q-apalis-eval-vga.dtbo
+
+imx6q-apalis-eval-vga-dtbs := \
+	imx6q-apalis-eval.dtb \
+	imx6q-apalis-eval-vga.dtbo
+
+imx6q-apalis-v1.2-eval-v1.2-vga-dtbs := \
+	imx6q-apalis-v1.2-eval-v1.2.dtb \
+	imx6q-apalis-eval-vga.dtbo
+
+imx6q-apalis-v1.2-eval-vga-dtbs := \
+	imx6q-apalis-v1.2-eval.dtb \
+	imx6q-apalis-eval-vga.dtbo
+
 imx6qdl-dhcom-pdk2-overlay-497-200-x12-dtbs := \
 	imx6q-dhcom-pdk2.dtb \
 	imx6qdl-dhcom-pdk2-overlay-497-200-x12.dtbo
@@ -186,11 +202,16 @@ dtb-$(CONFIG_SOC_IMX6Q) += \
 	imx6dl-yapp4-ursa.dtb \
 	imx6q-apalis-eval.dtb \
 	imx6q-apalis-eval-v1.2.dtb \
+	imx6q-apalis-eval-v1.2-vga.dtb \
+	imx6q-apalis-eval-vga.dtb \
+	imx6q-apalis-eval-vga.dtbo \
 	imx6q-apalis-ixora.dtb \
 	imx6q-apalis-ixora-v1.1.dtb \
 	imx6q-apalis-ixora-v1.2.dtb \
 	imx6q-apalis-v1.2-eval.dtb \
 	imx6q-apalis-v1.2-eval-v1.2.dtb \
+	imx6q-apalis-v1.2-eval-v1.2-vga.dtb \
+	imx6q-apalis-v1.2-eval-vga.dtb \
 	imx6q-apalis-v1.2-ixora.dtb \
 	imx6q-apalis-v1.2-ixora-v1.1.dtb \
 	imx6q-apalis-v1.2-ixora-v1.2.dtb \
diff --git a/arch/arm/boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso b/arch/arm/boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso
new file mode 100644
index 000000000000..991c2b7c2777
--- /dev/null
+++ b/arch/arm/boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Copyright (c) Toradex
+ *
+ * VGA output connected to a parallel RGB LCD interface through a
+ * non-programmable video DAC with a VGA connector.
+ *
+ * The VGA output is available on the Apalis Evaluation Board without VESA DDC
+ * I2C signals.
+ */
+
+/dts-v1/;
+/plugin/;
+
+&{/} {
+	disp1 {
+		compatible = "fsl,imx-parallel-display";
+		pinctrl-names = "default";
+		pinctrl-0 = <&pinctrl_ipu2_vdac>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		interface-pix-fmt = "rgb565";
+
+		port@0 {
+			reg = <0>;
+
+			vga_display_in: endpoint {
+				remote-endpoint = <&ipu2_di0_disp0>;
+			};
+		};
+
+		port@1 {
+			reg = <1>;
+
+			vga_display_out: endpoint {
+				remote-endpoint = <&vga_enc_in>;
+			};
+		};
+	};
+
+	vga-encoder {
+		compatible = "dumb-vga-dac";
+
+		ports {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			port@0 {
+				reg = <0>;
+
+				vga_enc_in: endpoint {
+					data-enable-active = <0>;
+					remote-endpoint = <&vga_display_out>;
+				};
+			};
+
+			port@1 {
+				reg = <1>;
+
+				vga_enc_out: endpoint {
+					remote-endpoint = <&vga_connector_in>;
+				};
+			};
+		};
+	};
+
+	vga-connector {
+		compatible = "vga-connector";
+
+		port {
+			vga_connector_in: endpoint {
+				remote-endpoint = <&vga_enc_out>;
+			};
+		};
+	};
+};
+
+&ipu2_di0_disp0 {
+	remote-endpoint = <&vga_display_in>;
+};

-- 
2.43.0

Re: [PATCH v2 3/3] ARM: dts: imx6q-apalis: Add VGA overlay

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] ARM: dts: imx6q-apalis: VGA data-enable-active ignored by simple-bridge
--

commit a66c8dd73182954ba43ed81cada90ae73edf93a0
Author: Leonardo Costa <leonardo.costa@toradex.com>

ARM: dts: imx6q-apalis: Add VGA overlay

This commit adds a device tree overlay for the VGA output on the Apalis
Evaluation Board, connecting the parallel RGB display interface to a
non-programmable video DAC and VGA connector with an active-low data-enable
signal, and wires up composite DTB targets in the Makefile.

> diff --git a/arch/arm/boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso b/arch/arm/boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso
> new file mode 100644
> index 0000000000000..991c2b7c27773
> --- /dev/null
> +++ b/arch/arm/boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso
> @@ -0,0 +1,80 @@

[ ... ]

> +	vga-encoder {
> +		compatible = "dumb-vga-dac";
> +
> +		ports {
> +			#address-cells = <1>;
> +			#size-cells = <0>;
> +
> +			port@0 {
> +				reg = <0>;
> +
> +				vga_enc_in: endpoint {
> +					data-enable-active = <0>;
> +					remote-endpoint = <&vga_display_out>;
> +				};
> +			};

[Severity: High]
Does data-enable-active = <0> on vga_enc_in actually reach the IPUv3
CRTC?

In simple_bridge_probe() in drivers/gpu/drm/bridge/simple-bridge.c, the
data-enable-active property is parsed into timings->input_bus_flags:

	if (de_present && !sbridge->bridge.timings) {
		struct drm_bridge_timings *timings;

		timings = devm_kzalloc(&pdev->dev, sizeof(*timings), GFP_KERNEL);
		if (!timings)
			return -ENOMEM;

		timings->input_bus_flags = de ? DRM_BUS_FLAG_DE_HIGH :
						DRM_BUS_FLAG_DE_LOW;
		sbridge->bridge.timings = timings;
	}

However, simple_bridge_bridge_funcs registers atomic bridge state
callbacks without an .atomic_check callback:

static const struct drm_bridge_funcs simple_bridge_bridge_funcs = {
	.atomic_create_state = drm_atomic_helper_bridge_create_state,
	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
	.attach		= simple_bridge_attach,
	.atomic_enable = simple_bridge_enable,
	.atomic_disable = simple_bridge_disable,
};

During drm_atomic_bridge_chain_check() ->
drm_atomic_bridge_propagate_bus_flags(), sbridge's
bridge_state->input_bus_cfg.flags is overwritten with the downstream
display-connector bridge's input_bus_cfg.flags (which is 0), and
sbridge->bridge.timings->input_bus_flags is never copied into
bridge_state->input_bus_cfg.flags.

Then, upstream in imx_pd_bridge_atomic_check() in
drivers/gpu/drm/imx/ipuv3/parallel-display.c:

	if (next_bridge)
		next_bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
								    next_bridge);

	if (next_bridge_state)
		bus_flags = next_bridge_state->input_bus_cfg.flags;
	else
		bus_flags = di->bus_flags;

Because next_bridge_state is non-NULL, bus_flags is read as 0 from
next_bridge_state->input_bus_cfg.flags without consulting
next_bridge->timings->input_bus_flags.

When ipu_crtc_mode_set_nofb() -> ipu_di_init_sync_panel() runs,
sig_cfg.enable_pol = !(imx_crtc_state->bus_flags & DRM_BUS_FLAG_DE_LOW)
evaluates to 1, driving the data-enable pin active-high instead of
active-low and gating off the VGA DAC output during active video.

Should simple-bridge implement .atomic_check to populate
bridge_state->input_bus_cfg.flags from bridge->timings->input_bus_flags
 so the active-low polarity is propagated to imx-parallel-display?

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261019-v2-apalis-imx6-enable-vga-v2-0-ef6a3a780472@toradex.com?part=3

Re: [PATCH v2 3/3] ARM: dts: imx6q-apalis: Add VGA overlay

[Frank Li]

On Mon, Oct 19, 2026 at 07:17:16AM -0300, Leonardo Costa wrote:
> From: Leonardo Costa <leonardo.costa@toradex.com>
>
> Add a device tree overlay for the VGA output available on the Apalis
> Evaluation Board, which is driven from a parallel RGB interface passing
> through a non-programmable video DAC to a VGA connector, without VESA
> DDC I2C signals.
>
> The non-programmable video DAC consists of a simple resistor ladder that
> converts the digital 16-bit RGB signal to VGA. The VGA output is gated by
> an active-low data-enable signal.
>
> The overlay is also combined with the various Apalis Evaluation Board
> device trees to provide ready-to-use DTBs.
>
> Signed-off-by: Leonardo Costa <leonardo.costa@toradex.com>
> ---
>  arch/arm/boot/dts/nxp/imx/Makefile                 | 21 ++++++
>  .../boot/dts/nxp/imx/imx6q-apalis-eval-vga.dtso    | 80 ++++++++++++++++++++++

what's difference with

https://lore.kernel.org/imx/20261019-colibri-imx6-overlays-v1-5-e4d028727382@toradex.com/T/#u

Is it possible share one dtso also?

Frank