proper_device_tree_design

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proper_device_tree_design [2018/11/18 10:28] – created rpjdayproper_device_tree_design [2018/11/18 10:46] (current) – [imx6ul-tx6ul-mainboard.dts] rpjday
Line 14: Line 14:
   * ''am335x-bonegreen-wireless.dts''   * ''am335x-bonegreen-wireless.dts''
  
 +===== Proper use of .dtsi files =====
  
 +There is **//no reason//** to make local copies of kernel-supplied ''.dtsi'' files and alter them; such files should be included as is, and //all// alterations should be made in the ''.dts'' file or a more general board-related ''.dtsi'' file supplied by that developer. Any alterations that involve actual //removal// of included content should be done via one of the two directives:
 +
 +  * ''/delete-property/''
 +  * ''/delete-node/''
 +
 +This functionality was introduced into the Linux kernel file ''scripts/dtc/dtc-lexer.l'' file in Sept of 2012:
 +
 +<file>
 +commit cd296721a9645f9f28800a072490fa15458d1fb7
 +Author: Stephen Warren <swarren@nvidia.com>
 +Date:   Fri Sep 28 21:25:59 2012 +0000
 +
 +    dtc: import latest upstream dtc
 +    
 +    This updates scripts/dtc to commit 317a5d9 "dtc: zero out new label
 +    objects" from git://git.jdl.com/software/dtc.git.
 +    
 +    This adds features such as:
 +    * /bits/ syntax for cell data.
 +    * Math expressions within cell data.
 +    * The ability to delete properties or nodes.
 +    * Support for #line directives in the input file, which allows the use of
 +      cpp on *.dts.
 +    * -i command-line option (/include/ path)
 +    * -W/-E command-line options for error/warning control.
 +    * Removal of spew to STDOUT containing the filename being compiled.
 +    * Many additions to the libfdt API.
 +    
 +    Signed-off-by: Stephen Warren <swarren@nvidia.com>
 +    Acked-by: Jon Loeliger <jdl@jdl.com>
 +    Signed-off-by: Rob Herring <rob.herring@calxeda.com>
 +</file>
 +
 +Examples can be seen [[https://elinux.org/Device_Tree_Source_Undocumented|here]].
 +
 +===== Examples of /delete-node/ =====
 +
 +==== imx6dl-tx6s-8034.dts ====
 +
 +<file>
 +#include "imx6dl.dtsi"
 +#include "imx6qdl-tx6.dtsi"
 +
 +/ {
 +        model = "Ka-Ro electronics TX6S-8034 Module";
 +        compatible = "karo,imx6dl-tx6dl", "fsl,imx6dl";
 +
 +        aliases {
 +                display = &display;
 +                ipu1 = &ipu1;
 +        };
 +
 +        cpus {
 +                /delete-node/ cpu@1;
 +        };
 +</file>
 +
 +==== imx6q-utilite-pro.dts ====
 +
 +<file>
 +#include <dt-bindings/input/input.h>
 +#include "imx6q-cm-fx6.dts"
 +
 +/ {
 +        model = "CompuLab Utilite Pro";
 +        compatible = "compulab,utilite-pro", "compulab,cm-fx6", "fsl,imx6q";
 +        
 + ...
 +
 +};
 +
 +/*
 + * A single IPU is not able to drive both display interfaces available on the
 + * Utilite Pro at high resolution due to its bandwidth limitation. Since the
 + * tfp410 encoder is wired up to IPU1, sever the link between IPU1 and the
 + * SoC-internal Designware HDMI encoder forcing the latter to be connected to
 + * IPU2 instead of IPU1.
 + */
 +/delete-node/&ipu1_di0_hdmi;
 +/delete-node/&hdmi_mux_0;
 +/delete-node/&ipu1_di1_hdmi;
 +/delete-node/&hdmi_mux_1;
 +</file>
 +
 +===== Examples of /delete-property/ =====
 +
 +==== imx6qp.dtsi ====
 +
 +<file>
 +#include "imx6q.dtsi"
 +
 +/ {
 +        soc {
 +        
 +        ...
 +        
 +};
 +
 +&fec {
 +        /delete-property/interrupts-extended;
 +        interrupts = <0 118 IRQ_TYPE_LEVEL_HIGH>,
 +                     <0 119 IRQ_TYPE_LEVEL_HIGH>;
 +};
 +</file>
 +
 +==== imx6ul-tx6ul-mainboard.dts ====
 +
 +<file>
 +#include "imx6ul.dtsi"
 +#include "imx6ul-tx6ul.dtsi"
 +
 +/ {
 +        model = "Ka-Ro electronics TXUL-0010 Module on TXUL Mainboard";
 +        compatible = "karo,imx6ul-tx6ul", "fsl,imx6ul";
 +
 +        aliases {
 +                lcdif_24bit_pins_a = &pinctrl_disp0_3;
 +                mmc0 = &usdhc1;
 +                /delete-property/ mmc1;
 +                serial2 = &uart3;
 +                serial4 = &uart5;
 +        };
 +        /delete-node/ sound;
 +};
 +
 +...
 +
 +&usdhc1 {
 +        pinctrl-0 = <&pinctrl_usdhc1>;
 +        non-removable;
 +        /delete-property/ cd-gpios;
 +        cap-sdio-irq;
 +};
 +
 +&uart1 {
 +        pinctrl-0 = <&pinctrl_uart1>;
 +        /delete-property/ uart-has-rtscts;
 +};
 +
 +&uart2 {
 +        pinctrl-0 = <&pinctrl_uart2>;
 +        /delete-property/ uart-has-rtscts;
 +        status = "okay";
 +};
 +</file>
 +
 +==== imx6ulz.dtsi ====
 +
 +<code>
 +#include "imx6ull.dtsi"
 +
 +/ {
 +        aliases {
 +                /delete-property/ ethernet0;
 +                /delete-property/ ethernet1;
 +                /delete-property/ i2c2;
 +                /delete-property/ i2c3;
 +                /delete-property/ serial4;
 +                /delete-property/ serial5;
 +                /delete-property/ serial6;
 +                /delete-property/ serial7;
 +                /delete-property/ spi2;
 +                /delete-property/ spi3;
 +        };
 +};
 +
 +/delete-node/ &adc1;
 +/delete-node/ &can1;
 +/delete-node/ &can2;
 +/delete-node/ &ecspi3;
 +/delete-node/ &ecspi4;
 +/delete-node/ &epit2;
 +/delete-node/ &gpt2;
 +/delete-node/ &i2c3;
 +/delete-node/ &i2c4;
 +/delete-node/ &pwm5;
 +/delete-node/ &pwm6;
 +/delete-node/ &pwm7;
 +/delete-node/ &pwm8;
 +/delete-node/ &uart5;
 +/delete-node/ &uart6;
 +/delete-node/ &uart7;
 +/delete-node/ &uart8;
 +</code>
  • proper_device_tree_design.1542536904.txt.gz
  • Last modified: 2018/11/18 10:28
  • by rpjday