By Toradex秦海

1). 简介

NXP i.MX8MP arm SoC 支持 3 路 Display Controller 分别提供 DSI/HDMI/LVDS 显示输出，在 Yocto Linux BSP 下采用 Wayland Backend 基于 DRM subsystem 显示驱动，前端默认基于 Weston Compositor。因此在默认情况下连接多个屏幕的显示输出是如下 Extended 模式：

而为了实现多屏幕 Clone Mode 显示，就需要修改显示 buffer 输出模式如下：

本文就基于上述显示输出 pipeline 修改测试 i.MX8MP 多屏 Clone Mode，本文所涉及的方法和实际修改代码均来自于如下 NXP 论坛文档，本文仅进行测试演示示例。

https://community.nxp.com/t5/i-MX-Graphics-Knowledge-Base/Weston-clone-mode-on-i-MX8MPlus/ta-p/1791853

本文所演示的平台来自于 Toradex Verdin i.MX8MP 嵌入式平台。

2. 准备

a). Verdin i.MX8MP ARM核心版配合Dahlia 载板，并连接调试串口用于测试。

b). Dahlia 载板分别由 DSI-HDMI 转接卡和 native HDMI 两个接口连接两台 HDMI 显示器以便于进行多屏显示测试。

3). 修改部署方法之一：通过 Yocto 编译部署

a). 考虑可维护性和易用性，此方法为推荐方法。

b). 首先参考这里说明创建 Yocto/Openembedded 编译框架，当前最新版本是对应于 Toradex Yocto Linux BSP 7.x 版本的 scarthgap-7.x.y branch。

c). 创建定制化 layer meta-customer-demos ，用于添加 Weston 源码修改相关 patch 文件。

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$ mkdir -p ../oe_core/layers/meta-customer-demos/conf

$ cd .../oe_core/layers/meta-customer-demos/conf

### create layer.conf file ###

# We have a conf and classes directory, append to BBPATH

BBPATH .= ":${LAYERDIR}"

# We have recipes-* directories, add to BBFILES

BBFILES += "${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"

BBFILE_COLLECTIONS += "customer-demos"

BBFILE_PATTERN_customer-demos = "^${LAYERDIR}/"

BBFILE_PRIORITY_customer-demos = "24"

# Let us add layer-specific bbappends which are only applied when that

# layer is included in our configuration

BBFILES += "${@' '.join('${LAYERDIR}/%s/recipes*/*/*.bbappend' % layer \

               for layer in BBFILE_COLLECTIONS.split())}"

# Add layer-specific bb files too

BBFILES += "${@' '.join('${LAYERDIR}/%s/recipes*/*/*.bb' % layer \

               for layer in BBFILE_COLLECTIONS.split())}"

LAYERDEPENDS_customer-demos = " \

    core \

    yocto \

    openembedded-layer gnome-layer multimedia-layer networking-layer \

"

LAYERSERIES_COMPAT_customer-demos = "hardknott honister kirkstone scarthgap"

---------------------------------------

d). 在定制化 layer meta-customer-demos 下面添加 Weston bbappend 文件，应用相应的 patch 文件

---------------------------------------

$ cd .../oe_core/layers/meta-customer-demos/

$ mkdir -p recipes-graphics/wayland/files

$ cd recipes-graphics/wayland

### cteate weston_12.0.4.imx.bbappend file ###

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"

SRC_URI += " \

    file://0001-weston-imx-12.0.4-LF6.6.52_2.2.0-clone-mode-8MP.patch \

"

---------------------------------------

e). 将如下 0001-weston-imx-12.0.4-LF6.6.52_2.2.0-clone-mode-8MP.patch 补丁文件复制到 “.../oe_core/layers/meta-customer-demos/recipes-graphics/wayland/files” 目录即可。原 NXP 论坛文档 patch 是基于 Weston 12.0.3 版本，这里对于 Yocto 环境配置的 12.0.4 版本做了一定的适配修改。

https://gitee.com/simonqin09/verdin-imx8mp-display-clone-mode/blob/master/0001-weston-imx-12.0.4-LF6.6.52_2.2.0-clone-mode-8MP.patch

f). 最终完整 meta-customer-demos layer 文件结构如下

meta-customer-demos

├── conf

│   └── layer.conf

├── recipes-graphics

│   └── wayland

│       ├── files

│       │   └── 0001-weston-imx-12.0.4-LF6.6.52_2.2.0-clone-mode-8MP.patch

│       └── weston_12.0.4.imx.bbappend

g). 修改 bblayers.conf 和 local.conf 文件

-------------------------------

### modify bblayer.conf ###

--- a/build/conf/bblayers.conf  

+++ b/build/conf/bblayers.conf  

@@ -34,7 +34,7 @@

   ${TOPDIR}/../layers/meta-openembedded/meta-python \

   ${TOPDIR}/../layers/meta-freescale-distro \

   ${TOPDIR}/../layers/meta-toradex-demos \

+  ${TOPDIR}/../layers/meta-customer-demos \

   \

   \

   ${TOPDIR}/../layers/meta-toradex-distro \

### add below to local.conf ###

# add Freescale EULA

ACCEPT_FSL_EULA = "1"

-------------------------------

h). 编译 Yocto Linux image

-------------------------------

### compile Reference-Multimedia image ###

$ MACHINE="verdin-imx8mp" bitbake tdx-reference-multimedia-image

-------------------------------

i). Yocto Linux image部署

参考这里通过Toradex Easy installer将上面编译好的image更新部署到模块

4). 修改部署方法之二：通过直接修改 Weston 源码编译部署

a). 在不具备 Yocto 编译条件下可以考虑此方法。

b). 参考如下下载对应版本 Weston-imx 源码，本文依然使用 12.0.4 版本示例，并进行修改

-------------------------------

### download weston-imx source code ###

$ git clone -b weston-imx-12.0.3 https://github.com/nxp-imx/weston-imx.git

### apply patch for clone mode ###

$ cd weston-imx

$ git apply ../../0001-weston-imx-12.0.4-LF6.6.52_2.2.0-clone-mode-8MP.patch

### modify meson.build file to adopt cross compile ###

$ vi protocol/meson.build

--- a/protocol/meson.build

+++ b/protocol/meson.build

@@ -1,5 +1,9 @@

 dep_scanner = dependency('wayland-scanner', native: false)

-prog_scanner = find_program(dep_scanner.get_variable(pkgconfig: 'wayland_scanner'))

+if meson.is_cross_build()

+       prog_scanner = find_program('wayland-scanner', dep_scanner.get_variable(pkgconfig: 'wayland_scanner'))

+else

+       prog_scanner = find_program(dep_scanner.get_variable(pkgconfig: 'wayland_scanner'))

+endif

 dep_wp = dependency('wayland-protocols', version: '>= 1.31',

        fallback: ['wayland-protocols', 'wayland_protocols'])

-------------------------------

c). 参考如下文章编译并 export 交叉编译 toolchain 相关环境变量

https://developer.toradex.cn/linux-bsp/os-development/build-yocto/linux-sdks

d). 编译修改好的 weston-imx 源码

-------------------------------

### export SDK environments ###

$ source <SDK_Install_Path>/environment-setup-armv8a-tdx-linux

### compile ###

$ cd weston-imx

$ meson build/ --prefix=/usr -Ddoc=false -Dbackend-drm-screencast-vaapi=false -Dcolor-management-lcms=false -Dpipewire=false \

-Dbackend-x11=false -Drenderer-g2d=true -Dbackend-pipewire=false -Dbackend-rdp=false -Dbackend-vnc=false -Dxwayland=false

$ DESTDIR=./opt/weston ninja -C build/ install

-------------------------------

e). 将编译好的 weston 相关库文件部署到 Verdin i.MX8MP BSP7.x Linux

-------------------------------

### package ###

$ cd weston-imx/build/opt/weston/

$ tar cjvf ../../../weston_mod.tar.bz2 *

### copy weston_mod.tar.bz2 package to Verdin i.MX8MP Linux ###

### deploy weston binaries ###

root@verdin-imx8mp-06849028:~# tar xvf weston_mod.tar.bz2 /

-------------------------------

5). 多屏显示测试

a). 上述修改部署完成后，不做任何修改，DSI-HDMI 和 native HDMI 屏幕默认启动后是 Extended 显示模式

b). 如下修改 /etc/xdg/weston/weston.ini 来使能 clone mode

-------------------------------

--- a/etc/xdg/weston/weston.ini

+++ b/etc/xdg/weston/weston.ini

@@ -3,6 +3,7 @@

 repaint-window=16

 idle-time=0

 #enable-overlay-view=1

+clone-mode=1

 [shell]

-------------------------------

c). 重新启动后 DSI-HDMI 和 native HDMI 屏幕使能为 Clone 显示模式

d). 另外，如果是 DSI/native HDMI/native LVDS 同时显示的话，根据 NXP 论坛原文说明，可以在 /etc/xdg/weston/weston.ini 文件中增加如下配置组合，实现两个屏幕 Clone mode 显示，另外一个屏幕 Extented mode 显示。

-------------------------------

...

clone-connector-id=<id_1>

extend-connector-id=<id_2>

[cloneoutput]

conn_id=<id_3>

mode=<display_resolution>

...

-------------------------------

// 其中屏幕 connector-id 通过如下 modetest 命令可以获取

-------------------------------

### get encoders devices ###

# Type DSI - DSI #

# Type TMDS - native HDMI #

root@verdin-imx8mp-06849028:~# modetest -M imx-drm |grep -C 5 Encoders                           

Encoders:

id      crtc    type    possible crtcs  possible clones

37      33      DSI     0x00000001      0x00000001

39      36      TMDS    0x00000002      0x00000002

Connectors:

### get display connector-ids ###

# connector-id 38 - DSI display #

# connector-id 40 - native HDMI display #

root@verdin-imx8mp-06849028:~# modetest -M imx-drm |grep -C 1 connected                          

id      encoder status          name            size (mm)       modes   encoders

38      37      connected       HDMI-A-1        0x0             12      37

  modes:

--

                value:

40      39      connected       HDMI-A-2        0x0             20      39

  modes:

-------------------------------

6). 总结

本文基于 NXP i.MX8MP 处理器平台测试了 Yocto Linux 下多屏幕 Clone 模式显示，不过请注意如 NXP 论坛原文说明，此方法仅限于 NXP i.MX8MP 平台应用。

参考文档

https://community.nxp.com/t5/i-MX-Graphics-Knowledge-Base/Weston-clone-mode-on-i-MX8MPlus/ta-p/1791853