Re: MXSFB error: -ENODEV: Cannot connect bridge

[Roland Hieber <rhi@pengutronix.de>]

On Thu, Feb 08, 2024 at 12:58:02PM -0300, Hiago De Franco wrote:
> Hello all,
> 
> while doing some tests with kernel v6.8-rc3 and Colibri iMX7D, we
> noticed the following error:
> 
> [    0.432547] mxsfb 30730000.lcdif: error -ENODEV: Cannot connect bridge
> 
> This was introduced by commit edbbae7fba495284f72f05768696572691231558
> ("ARM: dts: imx7: add MIPI-DSI support"). This patch is routing the
> lcdif to the mipi_dsi_in_lcdif endpoint, however we do not have the DSI
> pins available in our edge connector. Instead, we use the parallel RGB
> LCD interface directly with, as example, an external LVDS transmitter:
> 
> &lcdif {
> ...
> 	status = "disabled";
> 
> 	port {
> 		lcdif_out: endpoint {
> 			remote-endpoint = <&lcd_panel_in>;
> 		};
> 	};
> };
> 
> By applying the following patch, the issue is gone and the LVDS works
> again:
> 
> diff --git a/arch/arm/boot/dts/nxp/imx/imx7s.dtsi b/arch/arm/boot/dts/nxp/imx/imx7s.dtsi
> index ebf7befcc11e..9c81c6baa2d3 100644
> --- a/arch/arm/boot/dts/nxp/imx/imx7s.dtsi
> +++ b/arch/arm/boot/dts/nxp/imx/imx7s.dtsi
> @@ -834,16 +834,6 @@ lcdif: lcdif@30730000 {
>  					<&clks IMX7D_LCDIF_PIXEL_ROOT_CLK>;
>  				clock-names = "pix", "axi";
>  				status = "disabled";
> -
> -				port {
> -					#address-cells = <1>;
> -					#size-cells = <0>;
> -
> -					lcdif_out_mipi_dsi: endpoint@0 {
> -						reg = <0>;
> -						remote-endpoint = <&mipi_dsi_in_lcdif>;
> -					};
> -				};
>  			};
>  
>  			mipi_csi: mipi-csi@30750000 {
> @@ -895,22 +885,6 @@ mipi_dsi: dsi@30760000 {
>  				samsung,esc-clock-frequency = <20000000>;
>  				samsung,pll-clock-frequency = <24000000>;
>  				status = "disabled";
> -
> -				ports {
> -					#address-cells = <1>;
> -					#size-cells = <0>;
> -
> -					port@0 {
> -						reg = <0>;
> -						#address-cells = <1>;
> -						#size-cells = <0>;
> -
> -						mipi_dsi_in_lcdif: endpoint@0 {
> -							reg = <0>;
> -							remote-endpoint = <&lcdif_out_mipi_dsi>;
> -						};
> -					};
> -				};
>  			};
>  		};
> 
> I would like to know your opinion about this patch before sending it,
> does it makes sense for you? I understand that routing to endpoint
> should be done in the SoM device tree, so we are free to rout other
> endpoint without issues.

As far as I understood, the LCDIF -> DSI connection is always present in
the SoC. Can you overwrite the routing in your dts like this:?

    &lcdif_out_mipi_dsi {
        remote-endpoint = <&lcd_panel_in>;
    };

I'm not sure what is the best default solution here for imx7s.dtsi. Also
the labels don't work out in that case, this could be improved.

Regards,
 
 - Roland

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