Re: [PATCH v2 1/4] dt-bindings: lcdif: Add endpoint bus-width property

Re: [PATCH v2 1/4] dt-bindings: lcdif: Add endpoint bus-width property

[Frank Li]

On Thu, Jul 23, 2026 at 11:38:08AM +0200, Francesco Dolcini wrote:
> From: Francesco Dolcini <francesco.dolcini@toradex.com>
>
> The DPI output of the LCD interface can be configured with a bus width
> of 16, 18, or 24 bits. Introduce a bus-width property to the output
> endpoint, specifying the number of parallel RGB bits connected.
>
> Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> ---
> v2: use the common bus-width property instead of the legacy interface-pix-fmt
> ---
>  Documentation/devicetree/bindings/display/fsl,lcdif.yaml | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/fsl,lcdif.yaml b/Documentation/devicetree/bindings/display/fsl,lcdif.yaml
> index 2dd0411ec651..6931f0ae3829 100644
> --- a/Documentation/devicetree/bindings/display/fsl,lcdif.yaml
> +++ b/Documentation/devicetree/bindings/display/fsl,lcdif.yaml
> @@ -71,6 +71,15 @@ properties:
>      $ref: /schemas/graph.yaml#/properties/port
>      description: The LCDIF output port
>
> +    properties:
> +      endpoint:
> +        $ref: /schemas/graph.yaml#/$defs/endpoint-base

Is it better by use video-interfaces.yaml# ?

Frank

> +        unevaluatedProperties: false
> +
> +        properties:
> +          bus-width:
> +            enum: [ 16, 18, 24 ]
> +
>    display:
>      $ref: /schemas/types.yaml#/definitions/phandle
>      description: phandle to display panel
> --
> 2.47.3
>
>

Re: [PATCH v2 2/4] drm: mxsfb: Add optional DPI output bus-width configuration

[Frank Li]

On Thu, Jul 23, 2026 at 11:38:09AM +0200, Francesco Dolcini wrote:
> From: Francesco Dolcini <francesco.dolcini@toradex.com>
>
> LCDIF programs LCD_DATABUS_WIDTH from the selected media bus format. The
> format reported by the downstream panel or bridge describes the display
> input, but it does not describe how the LCDIF data pins are physically
> wired on the board.
>
> These can differ. For example, a 16-bit LCDIF bus can be connected to a
> 24-bit display by wiring the available color bits to the corresponding
> display inputs. In that case, using the display's 24-bit format to
> configure LCDIF selects the wrong data-bus mode and changes the assignment
> of color bits on the LCD_DATA pins.
>
> Read the optional bus-width endpoint property from the LCDIF output port
> and use it to select the media bus format used to configure LCDIF. This
> allows the LCDIF bus mode to describe the physical interface
> independently of the downstream display format.
>
> When the optional property is absent, continue using the format reported
> by the downstream display device, preserving the existing behavior.
>
> Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> ---
> v2: use the common bus-width property instead of the legacy interface-pix-fmt
> ---
>  drivers/gpu/drm/mxsfb/mxsfb_drv.c | 24 ++++++++++++++++++++++++
>  drivers/gpu/drm/mxsfb/mxsfb_drv.h |  2 ++
>  drivers/gpu/drm/mxsfb/mxsfb_kms.c | 12 ++++++++++++
>  3 files changed, 38 insertions(+)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> index 9b8fbda85d28..0545718a4b65 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> @@ -12,7 +12,10 @@
>  #include <linux/clk.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/io.h>
> +#include <linux/media-bus-format.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_graph.h>
>  #include <linux/platform_device.h>
>  #include <linux/property.h>
>  #include <linux/pm_runtime.h>
> @@ -209,7 +212,10 @@ static int mxsfb_load(struct drm_device *drm,
>  		      const struct mxsfb_devdata *devdata)
>  {
>  	struct platform_device *pdev = to_platform_device(drm->dev);
> +	struct device_node *np = pdev->dev.of_node;
>  	struct mxsfb_drm_private *mxsfb;
> +	struct device_node *ep;
> +	u32 bus_width = 0;
>  	int ret;
>
>  	mxsfb = devm_kzalloc(&pdev->dev, sizeof(*mxsfb), GFP_KERNEL);
> @@ -236,6 +242,24 @@ static int mxsfb_load(struct drm_device *drm,
>  	if (IS_ERR(mxsfb->clk_disp_axi))
>  		mxsfb->clk_disp_axi = NULL;
>
> +	ep = of_graph_get_next_endpoint(np, NULL);

use auto cleanup

	struct device_node *ep __free(device_node) = of_graph_get_next_endpoint(np, NULL);

Frank

> +	if (ep) {
> +		of_property_read_u32(ep, "bus-width", &bus_width);
> +		of_node_put(ep);
> +	}
> +
> +	switch (bus_width) {
> +	case 16:
> +		mxsfb->bus_format = MEDIA_BUS_FMT_RGB565_1X16;
> +		break;
> +	case 18:
> +		mxsfb->bus_format = MEDIA_BUS_FMT_RGB666_1X18;
> +		break;
> +	case 24:
> +		mxsfb->bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> +		break;
> +	}
> +
>  	ret = dma_set_mask_and_coherent(drm->dev, DMA_BIT_MASK(32));
>  	if (ret)
>  		return ret;
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.h b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
> index d160d921b25f..bdc47ce5be79 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.h
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.h
> @@ -46,6 +46,8 @@ struct mxsfb_drm_private {
>  	struct drm_connector		*connector;
>  	struct drm_bridge		*bridge;
>
> +	u32				bus_format;
> +
>  	bool				crc_active;
>  };
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> index d8ebebc5314b..1d78c486d147 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> @@ -386,6 +386,18 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,
>  	if (!bus_format)
>  		bus_format = MEDIA_BUS_FMT_RGB888_1X24;
>
> +	/*
> +	 * Prefer the bus format derived from the OF graph endpoint "bus-width"
> +	 * property when available. Otherwise, use the bus format reported by
> +	 * the downstream bridge or panel.
> +	 *
> +	 * This supports mismatched display and interface bus widths, such as
> +	 * a 24-bit panel connected through an 18-bit interface or an 18-bit
> +	 * panel connected through a 24-bit interface.
> +	 */
> +	if (mxsfb->bus_format)
> +		bus_format = mxsfb->bus_format;
> +
>  	mxsfb_crtc_mode_set_nofb(mxsfb, bridge_state, bus_format);
>
>  	/* Write cur_buf as well to avoid an initial corrupt frame */
> --
> 2.47.3
>
>

Re: [PATCH v2 2/4] drm: mxsfb: Add optional DPI output bus-width configuration

[Francesco Dolcini]

On Thu, Jul 23, 2026 at 10:47:36AM -0500, Frank Li wrote:
> On Thu, Jul 23, 2026 at 11:38:09AM +0200, Francesco Dolcini wrote:
> > From: Francesco Dolcini <francesco.dolcini@toradex.com>
> >
> > LCDIF programs LCD_DATABUS_WIDTH from the selected media bus format. The
> > format reported by the downstream panel or bridge describes the display
> > input, but it does not describe how the LCDIF data pins are physically
> > wired on the board.
> >
> > These can differ. For example, a 16-bit LCDIF bus can be connected to a
> > 24-bit display by wiring the available color bits to the corresponding
> > display inputs. In that case, using the display's 24-bit format to
> > configure LCDIF selects the wrong data-bus mode and changes the assignment
> > of color bits on the LCD_DATA pins.
> >
> > Read the optional bus-width endpoint property from the LCDIF output port
> > and use it to select the media bus format used to configure LCDIF. This
> > allows the LCDIF bus mode to describe the physical interface
> > independently of the downstream display format.
> >
> > When the optional property is absent, continue using the format reported
> > by the downstream display device, preserving the existing behavior.
> >
> > Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> > ---
> > v2: use the common bus-width property instead of the legacy interface-pix-fmt
> > ---
> >  drivers/gpu/drm/mxsfb/mxsfb_drv.c | 24 ++++++++++++++++++++++++
> >  drivers/gpu/drm/mxsfb/mxsfb_drv.h |  2 ++
> >  drivers/gpu/drm/mxsfb/mxsfb_kms.c | 12 ++++++++++++
> >  3 files changed, 38 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > index 9b8fbda85d28..0545718a4b65 100644
> > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > @@ -12,7 +12,10 @@
> >  #include <linux/clk.h>
> >  #include <linux/dma-mapping.h>
> >  #include <linux/io.h>
> > +#include <linux/media-bus-format.h>
> >  #include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/of_graph.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/property.h>
> >  #include <linux/pm_runtime.h>
> > @@ -209,7 +212,10 @@ static int mxsfb_load(struct drm_device *drm,
> >  		      const struct mxsfb_devdata *devdata)
> >  {
> >  	struct platform_device *pdev = to_platform_device(drm->dev);
> > +	struct device_node *np = pdev->dev.of_node;
> >  	struct mxsfb_drm_private *mxsfb;
> > +	struct device_node *ep;
> > +	u32 bus_width = 0;
> >  	int ret;
> >
> >  	mxsfb = devm_kzalloc(&pdev->dev, sizeof(*mxsfb), GFP_KERNEL);
> > @@ -236,6 +242,24 @@ static int mxsfb_load(struct drm_device *drm,
> >  	if (IS_ERR(mxsfb->clk_disp_axi))
> >  		mxsfb->clk_disp_axi = NULL;
> >
> > +	ep = of_graph_get_next_endpoint(np, NULL);
> 
> use auto cleanup
> 
> 	struct device_node *ep __free(device_node) = of_graph_get_next_endpoint(np, NULL);

Does it makes the code more read-able or better in this specific case? I
would say no, to me it is more compact and clear the way it is.

Re: [PATCH v2 2/4] drm: mxsfb: Add optional DPI output bus-width configuration

[Frank Li]

On Thu, Jul 23, 2026 at 05:53:32PM +0200, Francesco Dolcini wrote:
> On Thu, Jul 23, 2026 at 10:47:36AM -0500, Frank Li wrote:
> > On Thu, Jul 23, 2026 at 11:38:09AM +0200, Francesco Dolcini wrote:
> > > From: Francesco Dolcini <francesco.dolcini@toradex.com>
> > >
> > > LCDIF programs LCD_DATABUS_WIDTH from the selected media bus format. The
> > > format reported by the downstream panel or bridge describes the display
> > > input, but it does not describe how the LCDIF data pins are physically
> > > wired on the board.
> > >
> > > These can differ. For example, a 16-bit LCDIF bus can be connected to a
> > > 24-bit display by wiring the available color bits to the corresponding
> > > display inputs. In that case, using the display's 24-bit format to
> > > configure LCDIF selects the wrong data-bus mode and changes the assignment
> > > of color bits on the LCD_DATA pins.
> > >
> > > Read the optional bus-width endpoint property from the LCDIF output port
> > > and use it to select the media bus format used to configure LCDIF. This
> > > allows the LCDIF bus mode to describe the physical interface
> > > independently of the downstream display format.
> > >
> > > When the optional property is absent, continue using the format reported
> > > by the downstream display device, preserving the existing behavior.
> > >
> > > Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> > > ---
> > > v2: use the common bus-width property instead of the legacy interface-pix-fmt
> > > ---
> > >  drivers/gpu/drm/mxsfb/mxsfb_drv.c | 24 ++++++++++++++++++++++++
> > >  drivers/gpu/drm/mxsfb/mxsfb_drv.h |  2 ++
> > >  drivers/gpu/drm/mxsfb/mxsfb_kms.c | 12 ++++++++++++
> > >  3 files changed, 38 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > > index 9b8fbda85d28..0545718a4b65 100644
> > > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > > @@ -12,7 +12,10 @@
> > >  #include <linux/clk.h>
> > >  #include <linux/dma-mapping.h>
> > >  #include <linux/io.h>
> > > +#include <linux/media-bus-format.h>
> > >  #include <linux/module.h>
> > > +#include <linux/of.h>
> > > +#include <linux/of_graph.h>
> > >  #include <linux/platform_device.h>
> > >  #include <linux/property.h>
> > >  #include <linux/pm_runtime.h>
> > > @@ -209,7 +212,10 @@ static int mxsfb_load(struct drm_device *drm,
> > >  		      const struct mxsfb_devdata *devdata)
> > >  {
> > >  	struct platform_device *pdev = to_platform_device(drm->dev);
> > > +	struct device_node *np = pdev->dev.of_node;
> > >  	struct mxsfb_drm_private *mxsfb;
> > > +	struct device_node *ep;
> > > +	u32 bus_width = 0;
> > >  	int ret;
> > >
> > >  	mxsfb = devm_kzalloc(&pdev->dev, sizeof(*mxsfb), GFP_KERNEL);
> > > @@ -236,6 +242,24 @@ static int mxsfb_load(struct drm_device *drm,
> > >  	if (IS_ERR(mxsfb->clk_disp_axi))
> > >  		mxsfb->clk_disp_axi = NULL;
> > >
> > > +	ep = of_graph_get_next_endpoint(np, NULL);
> >
> > use auto cleanup
> >
> > 	struct device_node *ep __free(device_node) = of_graph_get_next_endpoint(np, NULL);
>
> Does it makes the code more read-able or better in this specific case? I
> would say no, to me it is more compact and clear the way it is.

Recently there are bunch of patch to fix miss of_put_node(). auto cleanup
help avoid manual to manage it and let us to force key part.

recently, perfer use fwnode_graph_get_next_endpoint() and other fwnode_xxx
node function.

it is also okay to keep use of_xxx() to align existing code.

Frank

>
>

Re: [PATCH v2 1/4] dt-bindings: lcdif: Add endpoint bus-width property

[Rob Herring]

On Thu, Jul 23, 2026 at 10:45:32AM -0500, Frank Li wrote:
> On Thu, Jul 23, 2026 at 11:38:08AM +0200, Francesco Dolcini wrote:
> > From: Francesco Dolcini <francesco.dolcini@toradex.com>
> >
> > The DPI output of the LCD interface can be configured with a bus width
> > of 16, 18, or 24 bits. Introduce a bus-width property to the output
> > endpoint, specifying the number of parallel RGB bits connected.
> >
> > Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> > ---
> > v2: use the common bus-width property instead of the legacy interface-pix-fmt
> > ---
> >  Documentation/devicetree/bindings/display/fsl,lcdif.yaml | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/display/fsl,lcdif.yaml b/Documentation/devicetree/bindings/display/fsl,lcdif.yaml
> > index 2dd0411ec651..6931f0ae3829 100644
> > --- a/Documentation/devicetree/bindings/display/fsl,lcdif.yaml
> > +++ b/Documentation/devicetree/bindings/display/fsl,lcdif.yaml
> > @@ -71,6 +71,15 @@ properties:
> >      $ref: /schemas/graph.yaml#/properties/port
> >      description: The LCDIF output port
> >
> > +    properties:
> > +      endpoint:
> > +        $ref: /schemas/graph.yaml#/$defs/endpoint-base
> 
> Is it better by use video-interfaces.yaml# ?

Yes.

Rob