View source for IMX8M Android Display

{{INIT_RELEASE_PARAM|RELEASE_Q10.0.0_1.0.0_GA_DART-MX8M}}<!--
--> {{#lst:Android_Platform_Customization|{{#var:RELEASE_PARAM}}}} <!--
--> {{PageHeader|DART-MX8M Display}} {{DocImage|category1=Android|category2=DART-MX8M}}__toc__

= Introduction =
== MIPI-DSI, LVDS and HDMI ==
i.MX8M supports MIPI-DSI, HDMI and DP displays. DART-MX8M can be optionally equipped with SN65DSI84 MIPI-DSI to LVDS bridge.<br>
DART-MX8M carrier board comes with LVDS, HDMI and DP connectors, so you can connect LVDS, HDMI or DP display.<br>
Dual LVDS+HDMI or LVDS+DP display configurations are also supported.<br>
Connecting MIPI-DSI display to DART-MX8M carrier board requires designing a custom connector.<br>

== DCSS vs LCDIF ==
i.MX8M comes with 2 display controllers: DCSS and LCDIF.<br>
DCCS can be connected to HDMI, DP or MIPI-DSI and supports resolutions up to 4K.<br>
LCDIF can be connected only to MIPI-DSI and supports resolutions up to 1080p.

{{#vardefine:DTB_PREFIX |{{#var:DTB_PREFIX | fsl-imx8mq-var-dart }}}}
= Selecting display configuration =
Selecting display configuration is a matter of selecting an appropriate DTB file.<br>
All available DTB files are listed in the table below.<br>
{{#lst:Yocto_Platform_Customization|{{#var:FDT_TABLE_SECTION}}}}
<br>
{{#ifeq: {{#var:YOCTO_NAME}} | Morty |
File /boot/imx8m-var-dart.dtb is a symbolic link to the active DTB file. By default DCSS+LVDS display is used.<br>
For example, to select HDMI display in EMMC+WIFI configuration, run the following commands:

 # cd /boot
 # ln -fs imx8m-var-dart-emmc-wifi-hdmi.dtb imx8m-var-dart.dtb
|{{#ifeq: {{#var:FSL_BSP_VERSION}} | L4.14.78-1.0.0_ga |
File /boot/{{#var:DTB_PREFIX}}.dtb is a symbolic link to the active DTB file. By default LVDS display is used.<br>
For example, to select HDMI display in EMMC+WIFI configuration, run the following commands:

 # cd /boot
 # ln -fs {{#var:DTB_PREFIX}}-emmc-wifi-hdmi.dtb {{#var:DTB_PREFIX}}.dtb
|
File /boot/{{#var:DTB_PREFIX}}.dtb is a symbolic link to the active DTB file. By default LVDS display is used.<br>
For example, to select HDMI display in WIFI configuration, run the following commands:

 # cd /boot
 # ln -fs {{#var:DTB_PREFIX}}-wifi-hdmi.dtb {{#var:DTB_PREFIX}}.dtb
}}
}}
Reboot is required for new configuration to take effect.

= Setting HDMI display resolution =
{{#ifeq: {{#var:YOCTO_NAME}} | Morty |
The default HDMI display resolution is 1080P. This setting is passed to the Linux kernel via "video" command line parameter.
|{{#ifeq: {{#var:FSL_BSP_VERSION}} | L4.14.78-1.0.0_ga |
The default HDMI display resolution is 1080P. This setting is passed to the Linux kernel via "video" command line parameter.
|
By default the maximum resolution supported by HDMI display is used.
}}
}}

To check the current resolution, use fbset command:
<pre>
root@imx8m-var-dart:~# fbset

mode "1920x1080"
    geometry 1920 1080 1920 1080 32
    timings 0 0 0 0 0 0 0
    accel true
    rgba 8/16,8/8,8/0,0/0
endmode
</pre>

{{#ifeq: {{#var:YOCTO_NAME}} | Morty |
To modify HDMI display resolution use fw_setenv command to set "video" parameter in the u-boot environment.<br>
For example, to set 4K@60fps resolution, run

 # fw_setenv video HDMI-A-1:3840x2160-32@60
|{{#ifeq: {{#var:FSL_BSP_VERSION}} | L4.14.78-1.0.0_ga |
To modify HDMI display resolution use fw_setenv command to set "video" parameter in the u-boot environment.<br>
For example, to set 4K@60fps resolution, run

 # fw_setenv video HDMI-A-1:3840x2160-32@60
|
To modify HDMI display resolution use fw_setenv command to set "video" kernel parameter.<br>
For example, to set 1080P@60fps resolution, run

 # fw_setenv kernelargs video=HDMI-A-1:1920x1080-32@60
}}
}}

The setting will take effect after reboot.

{{#ifeq: {{#var:FSL_BSP_VERSION}} | L4.14.98-2.0.0_ga |
= Setting DP display resolution =

By default the maximum resolution supported by DP display is used.

To modify DP display resolution use fw_setenv command to set "video" kernel parameter.<br>
For example, to set 1080P@60fps resolution, run

 # fw_setenv kernelargs video=DP-1:1920x1080-32@60
}}

= Setting Weston desktop resolution =
The default Weston desktop resolution is 1080P. This setting is independent of actual display resolution.<br>
{{#ifeq: {{#var:YOCTO_NAME}} | Morty |
To modify Weston resolution, edit /etc/default/weston and set DESKTOP_SHELL_WINDOW parameter.<br>
For example, to set 4K resolution

 DESKTOP_SHELL_WINDOW=3840x2160
|
To modify Weston resolution, edit /etc/xdg/weston/weston.ini and set size parameter in shell section.<br>
For example, to set 4K resolution

 [shell]
 size=3840x2160
}}
For new setting to take effect restart weston by running

 # systemctl restart weston

= Dual display configuration =
In dual display configuration Weston desktop is running on LVDS display and HDMI display is blank.<br>
To play video on HDMI display the following command can be used:

 # {{#var: GPLAY_KMSSINK_CMD | gplay-1.0 --video-sink=kmssink video.mp4 }}

To play video on LVDS display the following command can be used:

 # gplay-1.0 --video-sink=waylandsink video.mp4

= Adding custom LVDS panel =
DART-MX8M evaluation kit comes with 800x480 LCD panel. DART-MX8M DTS files were created with this panel in mind.
To support your custom LVDS panel, you should make several modifications

{{#ifeq: {{#var:YOCTO_NAME}} | Morty |
== Adding panel definitions to panel driver ==
The following code snippets define Variscite panel in drivers/gpu/drm/panel/panel-simple.c in Linux kernel source:

<pre>
static const struct drm_display_mode sgd_gktw70sdae4sd_mode = {
	.clock = 29250,
	.hdisplay = 800,
	.hsync_start = 800 + 40,
	.hsync_end = 800 + 40 + 48,
	.htotal = 800 + 40 + 48 + 40,
	.vdisplay = 480,
	.vsync_start = 480 + 23,
	.vsync_end = 480 + 23 + 3,
	.vtotal = 480 + 23 + 3 + 39,
	.vrefresh = 60,
	.flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
};

static const struct panel_desc_dsi sgd_gktw70sdae4sd = {
	.desc = {
		.modes = &sgd_gktw70sdae4sd_mode,
		.num_modes = 1,
		.bpc = 8,
		.size = {
			.width = 154,
			.height = 87,
		},
		.bus_flags = DRM_BUS_FLAG_DE_LOW,
	},
	.flags = MIPI_DSI_MODE_VIDEO,
	.format = MIPI_DSI_FMT_RGB888,
	.lanes = 4,
};

static const struct of_device_id dsi_of_match[] = {
 ...
	}, {
		.compatible = "sgd,gktw70sdae4sd",
		.data = &sgd_gktw70sdae4sd
	}, {
		/* sentinel */
	}
};
</pre>

You should add definitions of your panel and rebuild the kernel.

== Referencing custom panel in the DTS file ==
The following code references Variscite panel in arch/arm64/boot/dts/variscite/imx8m-var-dart-common.dtsi under kernel source tree

<pre>
&mipi_dsi_bridge {
	...
	panel@0 {
                reg = <0>;
                status = "okay";
                compatible = "sgd,gktw70sdae4sd";
                backlight = <&backlight>;
		dsi-lanes = <4>;
		panel-width-mm  = <154>;
		panel-height-mm = <87>;

		port {
			panel_in: endpoint {
				remote-endpoint = <&mipi_dsi_bridge_out>;
			};
		};
	};
        ...
};
</pre>

You should modify "compatible", "dsi-lanes", "panel-width-mm" and "panel-height-mm" properties to match your panel and rebuild DTB files.

== Configuring MIPI-DSI to LVDS bridge ==
MIPI-DSI to LVDS bridge configuration in arch/arm64/boot/dts/variscite/imx8m-var-dart-common.dtsi matches Variscite panel:

<pre>
	dsi_lvds_bridge: sn65dsi84@2c {
	        ...
		sn65dsi84,addresses = <	0x09 0x0A 0x0B 0x0D 0x10 0x11 0x12 0x13
					0x18 0x19 0x1A 0x1B 0x20 0x21 0x22 0x23
					0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B
					0x2C 0x2D 0x2E 0x2F 0x30 0x31 0x32 0x33
					0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B
					0x3C 0x3D 0x3E 0x0D>;

		sn65dsi84,values =    <	0x00 0x01 0x10 0x00 0x26 0x00 0x11 0x00
					0x7a 0x00 0x03 0x00 0x20 0x03 0x00 0x00
					0x00 0x00 0x00 0x00 0x21 0x00 0x00 0x00
					0x30 0x00 0x00 0x00 0x03 0x00 0x00 0x00
					0x28 0x00 0x00 0x00 0x00 0x00 0x00 0x00
					0x00 0x00 0x00 0x01>;
	};
};
</pre>

Use TI DSI Tuner application http://www.ti.com/tool/DSI-TUNER to generate bridge configuration for your panel and rebuild DTB files.<br>
Documentation on MIPI-DSI to LVDS bridge is available here: http://www.ti.com/product/sn65dsi84
|
The following code references Variscite panel in arch/arm64/boot/dts/freescale/{{#var:DTB_PREFIX}}-common.dtsi under kernel source tree

<pre>
	dsi_lvds_bridge: sn65dsi84@2c {
		compatible = "ti,sn65dsi83";
		reg = <0x2c>;
		ti,dsi-lanes = <1>;
		ti,lvds-format = <1>;
		ti,lvds-bpp = <24>;
		ti,width-mm = <154>;
		ti,height-mm = <87>;
		enable-gpios = <&gpio1 11 GPIO_ACTIVE_HIGH>;
		pinctrl-names = "default";
		pinctrl-0 = <&pinctrl_lvds>;
		status = "okay";

		display-timings {
			lvds {
				clock-frequency = <33000000>;
				hactive = <800>;
				vactive = <480>;
				hback-porch = <40>;
				hfront-porch = <40>;
				vback-porch = <29>;
				vfront-porch = <13>;
				hsync-len = <48>;
				vsync-len = <3>;
				hsync-active = <0>;
				vsync-active = <0>;
				de-active = <1>;
				pixelclk-active = <0>;
			};
		};
        ...
        };
</pre>

You should modify "ti,dsi-lanes", "ti,lvds-format", "ti,lvds-bpp", "ti,width-mm", "ti,height-mm" and "display-timings" properties to match your panel specification and rebuild the DTB file.<br>
To support dual channel LVDS panel, please add "ti,lvds-channels = <2>" property. Also, for dual channel LVDS panels clock frequency and horizontal parameters mentioned in panel datasheet should be doubled.
}}