Re: [PATCH 2/2] arm64: dts: freescale: Add LVDS overlay for TQMa8MPxL

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Hello Richard,

Am Dienstag, 20. Dezember 2022, 09:48:45 CET schrieb Richard Leitner:
> Hi Alexander,
> 
> thanks for the series.
> 
> On Thu, Dec 08, 2022 at 10:08:42AM +0100, Alexander Stein wrote:
> > This adds an overlay for the supported LVDS display tianma tm070jvhg33.
> > The display timings have to be specified explicitly. Using the typical
> > pixel clock, the LDB clock can not be configured as the 7-fold of that.
> > By setting pixel clock to 74.25 MHz, LDB can be configured to exactly
> > 519.75 MHz.
> > 
> > Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> > ---
> > To be hold I'm unsure where to list the overlays. I checked other overlays
> > and opted to added them at the end of imx8mp section.
> > 
> >  arch/arm64/boot/dts/freescale/Makefile        |  4 ++
> >  .../imx8mp-tqma8mpql-mba8mpxl-lvds.dtso       | 61 +++++++++++++++++++
> >  2 files changed, 65 insertions(+)
> >  create mode 100644
> >  arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtso
> ...
> 
> > diff --git
> > a/arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtso
> > b/arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtso new
> > file mode 100644
> > index 0000000000000..ea44d605342ba
> > --- /dev/null
> > +++ b/arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtso
> > @@ -0,0 +1,61 @@
> > +// SPDX-License-Identifier: (GPL-2.0-or-later OR MIT)
> > +/*
> > + * Copyright (c) 2022 TQ-Systems GmbH <linux@ew.tq-group.com>,
> > + * D-82229 Seefeld, Germany.
> > + * Author: Alexander Stein
> > + */
> > +
> > +/dts-v1/;
> > +/plugin/;
> > +
> > +&{/} {
> > +	compatible = "tq,imx8mp-tqma8mpql-mba8mpxl", "tq,imx8mp-tqma8mpql",
> > "fsl,imx8mp"; +};
> > +
> > +&backlight_lvds {
> > +	status = "okay";
> > +};
> > +
> > +&display {
> > +	compatible = "tianma,tm070jvhg33";
> > +	status = "okay";
> > +
> > +	panel-timing {
> > +		clock-frequency = <74250000>;
> > +		hactive = <1280>;
> > +		vactive = <800>;
> > +		hfront-porch = <64>;
> > +		hback-porch = <5>;
> > +		hsync-len = <1>;
> > +		vfront-porch = <40>;
> > +		vback-porch = <2>;
> > +		vsync-len = <1>;
> > +		de-active = <1>;
> > +	};
> > +
> > +	port {
> > +		panel_in_lvds0: endpoint {
> > +			remote-endpoint = <&ldb_lvds_ch0>;
> > +		};
> > +	};
> > +};
> > +
> > +&lcdif2 {
> > +	status = "okay";
> > +};
> > +
> > +&lvds_bridge {
> > +	status = "okay";
> > +
> > +	ports {
> > +		port@1 {
> > +			ldb_lvds_ch0: endpoint {
> > +				remote-endpoint = <&panel_in_lvds0>;
> > +			};
> > +		};
> > +	};
> > +};
> 
> Wouldn't it be possible and easier to read if this was &ldb_lvds_ch0
> only instead of the "whole" &lvds_bridge?
> 
> &ldb_lvds_ch0 {
> 	remote-endpoint = <&panel_in_lvds0>;
> };

Yes it is possible and easier to read. Unfortunately dtbs_check will raise the 
follwing warnings when doing so:
> arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtbo: Warning 
(graph_port): /fragment@4: graph port node name should be 'port'
> ../arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtso:
47.15-49.3: Warning (graph_endpoint): /fragment@4/__overlay__: graph endpoint 
node name should be 'endpoint'
> ../arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtso:
47.15-49.3: Warning (graph_endpoint): /fragment@4/__overlay__: graph 
connection to node '/fragment@2/__overlay__/port/endpoint' is not 
bidirectional

I'm not sure which way is the preferred/correct one or if this is just an 
issue in dtc, raising the warnings.

Best regards,
Alexander

> > +
> > +&pwm2 {
> > +	status = "okay";
> > +};
> 
> regards;rl