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The default enabled display interface for the phyCORE-AM572x Rapid Development kit is the parallel display port utilizing a PHYTEC LCD Kit (LCD-018-070KAP). To enable use of HDMI with the Linux demo, the Linux device tree file will need to be modified. The following provides a walkthrough for modifying and rebuilding the device tree binary to enable HDMI. 

Step-by-step guide

• You will need to have a working build of the BSP to modify the device tree source file. Instructions for building the BSP are provided in the Quickstart guide: BSP-Yocto-TISDK-AM57xx-PD17.1.1 Quickstart
• On your Host PC navigate to the Linux source. The path to the source may differ on your machine. The following example path should be valid if you have completed the QuickStart and still have your terminal open.

cd $YOCTO_DIR/build/arago-tmp-external-linaro-toolchain/work/am572x_phycore_rdk-linux-gnueabi/linux-phytec-ti/4.4.32+git_v4.4.32-phy2-r7a/git/

• Open the device tree source file (am57xx-phycore-rdk.dts) in your favorite Linux text editor. vim for an example in this article.

vim arch/arm/boot/dts/am57xx-phycore-rdk.dts

• In the device tree source (DTS) file, find and change the display0 binding to HDMI. 

/ {
	memory {
		device_type = "memory";
		reg = <0x0 0x80000000 0x0 0x80000000>; /* 2GiB */
	};

	aliases {
		display0 = &hdmi;

/*		sound0 = &hdmi; */
		sound0 = &rdk_audio;
	};
};

• In the DTS file, disable LCD and enable HDMI bindings. The changes should look like the following.

/* FIXME: RR - HDMI, DSS, and LCD are disabled until
 *             the omapdrm-pvr build issues are resolved
 */

/* LCD-018 display: enable lcd0, backlight, and ft5406 */
&lcd0 {
	status = "disabled";
};
&backlight {
	status = "disabled";
};
&ft5406 {
	status = "disabled";
};
&lcd_port {
	status = "disabled";
};

/* HDMI: enable hdmi, hdmi0 and tpd12s521 */
&tpd12s521 {
	status = "okay";
};
&hdmi {
	status = "okay";
};
&hdmi0 {
	status = "okay";
};

&dss {
	status = "okay";
};

• Save and exit the DTS file. If you are using vim as your text editor use ':wq' to write-quit.
• Navigate back to the build directory to initiate a re-build of the kernel. 

cd $YOCTO_DIR/build/

• Re-build the kernel using the following commands. These commands will rebuild the kernel (zImage) and device tree binary (DTB). 

bitbake linux-phytec-ti -f -c compile && bitbake linux-phytec-ti

• The newly built images will be available here: $YOCTO_DIR/build/arago-tmp-external-linaro-toolchain/deploy/images/<machine>/zImage-am572x-phycore-rdk.dtb. Update your software to include the new device tree binary (DTB). For more details on how see the Quickstart Guide: BSP-Yocto-TISDK-AM57xx-PD17.1.1 Quickstart

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