1). 簡介

NXP i.MX8MP ARM SoC 支持 3 路 Display Controller 分別提供 DSI/HDMI/LVDS 顯示輸出，在 Yocto Linux BSP 下采用 Wayland Backend 基于 DRM subsystem 顯示驅(qū)動，前端默認(rèn)基于 Weston Compositor。因此在默認(rèn)情況下連接多個屏幕的顯示輸出是如下 Extended 模式：

而為了實現(xiàn)多屏幕 Clone Mode 顯示，就需要修改顯示 buffer 輸出模式如下：

本文就基于上述顯示輸出 pipeline 修改測試 i.MX8MP 多屏 Clone Mode，本文所涉及的方法和實際修改代碼均來自于如下 NXP 論壇文檔，本文僅進行測試演示示例。

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

本文所演示的平臺來自于 Toradex Verdin i.MX8MP 嵌入式平臺。

2. 準(zhǔn)備

a). Verdin i.MX8MP ARM核心版配合Dahlia 載板，并連接調(diào)試串口用于測試。

b). Dahlia 載板分別由 DSI-HDMI 轉(zhuǎn)接卡和 native HDMI 兩個接口連接兩臺 HDMI 顯示器以便于進行多屏顯示測試。

3). 修改部署方法之一：通過 Yocto 編譯部署

a). 考慮可維護性和易用性，此方法為推薦方法。

b). 首先參考這里說明創(chuàng)建 Yocto/Openembedded 編譯框架，當(dāng)前最新版本是對應(yīng)于 Toradex Yocto Linux BSP 7.x 版本的 scarthgap-7.x.y branch。

c). 創(chuàng)建定制化 layer meta-customer-demos ，用于添加 Weston 源碼修改相關(guān) patch 文件。

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

$ 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，應(yīng)用相應(yīng)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). 將如下 0001-weston-imx-12.0.4-LF6.6.52_2.2.0-clone-mode-8MP.patch 補丁文件復(fù)制到 “.../oe_core/layers/meta-customer-demos/recipes-graphics/wayland/files” 目錄即可。原 NXP 論壇文檔 patch 是基于 Weston 12.0.3 版本，這里對于 Yocto 環(huán)境配置的 12.0.4 版本做了一定的適配修改。

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). 最終完整 meta-customer-demos layer 文件結(jié)構(gòu)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). 編譯 Yocto Linux image

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

### compile Reference-Multimedia image ###

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

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

i). Yocto Linux image部署

參考這里通過Toradex Easy installer將上面編譯好的image更新部署到模塊

4). 修改部署方法之二：通過直接修改 Weston 源碼編譯部署

a). 在不具備 Yocto 編譯條件下可以考慮此方法。

b). 參考如下下載對應(yīng)版本 Weston-imx 源碼，本文依然使用 12.0.4 版本示例，并進行修改

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

### 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). 參考如下文章編譯并 export 交叉編譯 toolchain 相關(guān)環(huán)境變量

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

d). 編譯修改好的 weston-imx 源碼

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

### export SDK environments ###

$ source/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). 將編譯好的 weston 相關(guān)庫文件部署到 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). 多屏顯示測試

a). 上述修改部署完成后，不做任何修改，DSI-HDMI 和 native HDMI 屏幕默認(rèn)啟動后是 Extended 顯示模式

b). 如下修改 /etc/xdg/weston/weston.ini 來使能 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). 重新啟動后 DSI-HDMI 和 native HDMI 屏幕使能為 Clone 顯示模式

d). 另外，如果是 DSI/native HDMI/native LVDS 同時顯示的話，根據(jù) NXP 論壇原文說明，可以在 /etc/xdg/weston/weston.ini 文件中增加如下配置組合，實現(xiàn)兩個屏幕 Clone mode 顯示，另外一個屏幕 Extented mode 顯示。

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

...

clone-connector-id=

extend-connector-id=

[cloneoutput]

conn_id=

mode=

...

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

// 其中屏幕 connector-id 通過如下 modetest 命令可以獲取

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

### 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). 總結(jié)

本文基于 NXP i.MX8MP 處理器平臺測試了 Yocto Linux 下多屏幕 Clone 模式顯示，不過請注意如 NXP 論壇原文說明，此方法僅限于 NXP i.MX8MP 平臺應(yīng)用。

參考文檔

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