一 說明

不帶GPU功能，只能使用linuxFB方式運行QT程序

STM32MP15-Ecosystem-v2.1.0 release

tf-a-stm32mp-2.2.r2-r0

u-boot-stm32mp-2020.01.r2-r0

linux-stm32mp-5.4.56-r0

Buildroot: buildroot-2021.02.10

tslib: tslib-1.22

qt-everywhere-src-5.12.10

qt-opensource-linux-x64-5.12.10.run

Arm GNU Toolchain: gcc-arm-9.2-2019.12-x86_64-arm-none-linux-gnueabihf

二 屏幕驅動

屏幕是800x480的RGB-LCD，與開發板的硬件接口與ST官方開發板STM32MP157-EVAL的RGB-LTDC接口引腳一致。

首先修改設備樹文件arch/arm/boot/dts/stm32mp157d-custom.dts：

根節點添加panel_backlight和panel_rgb節點

/ {

......

panel_backlight: panel-backlight {

        compatible = 'pwm-backlight';

        pwms = <&pwm4 1 5000000>;

        brightness-levels = <0 32 64 96 128 160 192 224 255>;

        power-supply = <&v3v3>;

        default-brightness-level = <7>;

        status = 'okay';

    };

    panel_rgb: panel-rgb {

        compatible = 'custom,rgb-lcd5';

        backlight = <&panel_backlight>;

        status = 'okay';

        port {

            rgb_panel_in: endpoint {

                remote-endpoint = <<dc_ep0_out>;

            };

        };

};

    ......

};

<dc節點追加內容如下：

<dc {

pinctrl-names = 'default', 'sleep';

pinctrl-0 = <<dc_pins_b>;

pinctrl-1 = <<dc_pins_sleep_b>;

    status = 'okay';

    port {

        #address-cells = <1>;

        #size-cells = <0>;

        ltdc_ep0_out: endpoint@0 {

            reg = <0>;

            remote-endpoint = <&rgb_panel_in>;

        };

    };

};

接著修改設備樹文件arch/arm/boot/dts/stm32mp157d-custom.dtsi:

&timers4節點追加用于控制屏幕背光的內容如下

&timers4 {

    status = 'okay';

    /* spare dmas for other usage */

    /delete-property/dmas;

    /delete-property/dma-names;

    pwm4: pwm {

        pinctrl-0 = <&pwm4_pins_b>;

        pinctrl-1 = <&pwm4_sleep_pins_b>;

        pinctrl-names = 'default', 'sleep';

        #pwm-cells = <2>;

        status = 'okay';

    };

};

接著修改屏幕驅動文件drivers/gpu/drm/panel/panel-simple.c:

platform_of_match數組中添加自己屏幕的匹配數據

static const struct of_device_id platform_of_match[] = {

    ......

    {

.compatible = 'custom,rgb-lcd5',

.data = &custom_rgb_lcd5_desc,

},{

/* sentinel */

}

};

添加自己屏幕的時序參數及相關描述信息

static const struct drm_display_mode custom_rgb_lcd5_mode = {

.clock = 33300, /* LCD像素時鐘，單位：KHz */

.hdisplay = 800, /* LCD X軸像素個數 */

.hsync_start = 800 + 88, /* LCD X軸 + hbp 像素個數 */

.hsync_end = 800 + 88 + 48, /* LCD X軸 + hbp + hspw 像素個數*/

.htotal = 800 + 88 + 48 + 40,         /* LCD X軸 + hbp + hspw + hfp */

.vdisplay = 480, /* LCD Y軸像素個數 */

.vsync_start = 480 + 32, /* LCD Y軸 + vbp 像素個數 */

.vsync_end = 480 + 32 + 3, /* LCD Y軸 + vbp + vspw 像素個數 */

.vtotal = 480 + 32 + 3 + 13,         /* LCD Y軸 + vbp + vspw + vfp */

.vrefresh = 60, /* LCD刷新率，單位：HZ */

.flags = DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC,

};

static const struct panel_desc custom_rgb_lcd5_desc = {

.modes = &custom_rgb_lcd5_mode,

.num_modes = 1,

.bpc = 8,

.size = {

.width = 117,

.height = 67,

},

.bus_format = MEDIA_BUS_FMT_RGB888_1X24,

};

三 觸摸驅動

我手上開發板配套的RGB-LCD使用的觸摸芯片型號為GT9147，通信接口使用的是開發板的i2c2，除此之外還有RST復位引腳和IRQ中斷引腳。為了使Linux內核匹配該設備驅動，需要修改arch/arm/boot/dts/stm32mp157d-custom.dts設備樹文件。在&i2c2節點下追加如下內容：

&i2c2 {

    pinctrl-names = 'default', 'sleep';

pinctrl-0 = <&i2c2_pins_a>;

pinctrl-1 = <&i2c2_pins_sleep_a>;

i2c-scl-rising-time-ns = <185>;

i2c-scl-falling-time-ns = <20>;

clock-frequency = <400000>;

status = 'okay';

/* spare dmas for other usage */

/delete-property/dmas;

/delete-property/dma-names;

    goodix_ts: gt9147@14 {

compatible = 'goodix,gt9147';

reg = <0x14>;

        interrupt-parent = <&gpioe>;

        interrupts = <1 IRQ_TYPE_EDGE_RISING>;

irq-gpios = <&gpioe 1 GPIO_ACTIVE_HIGH>;

reset-gpios = <&gpioa 14 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;

status = 'okay';

};

};

Linux源碼中已有gt9147的驅動文件drivers/input/touchscreen/goodix.c，只需要配置內核使能該驅動即可。該驅動文件匹配列表如下：

static const struct of_device_id goodix_of_match[] = {

{ .compatible = 'goodix,gt1151' },

{ .compatible = 'goodix,gt5663' },

{ .compatible = 'goodix,gt5688' },

{ .compatible = 'goodix,gt911' },

{ .compatible = 'goodix,gt9110' },

{ .compatible = 'goodix,gt912' },

{ .compatible = 'goodix,gt927' },

{ .compatible = 'goodix,gt9271' },

{ .compatible = 'goodix,gt928' },

{ .compatible = 'goodix,gt967' },

{ .compatible = 'goodix,gt9147',},

{ }

};

四 測試顯示和觸摸

4.1 配置Linux

1、使能DRM(Direct Rendering Module)驅動（st源碼默認配置已使能配置）

Device Drivers  --->

Graphics support  ---> 

<*> Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)  --->

<*> DRM Support for STMicroelectronics SoC Series

Display Panels  ---> 

<*> support for simple panels

Backlight & LCD device support  --->

<*>   Generic PWM based Backlight Driver

開啟DRM驅動的傳統FB(FrameBuffer)框架：

Device Drivers  ---> 

Graphics support  ---> 

<*> Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)  --->  

[*]   Enable legacy fbdev support for your modesetting driver  

2、使能Goodix I2C觸摸芯片驅動（st源碼默認配置已使能配置）

Device Drivers  --->  

Input device support  ---> 

[*]   Touchscreens  ---> 

<*>   Goodix I2C touchscreen

4.2 配置Buildroot

1、使能libdrm庫用來調用DRM驅動測試屏幕

Target packages  ---> 

Libraries  --->  

Graphics  --->   

        [*] libdrm  ---> 

        [*]   Install test programs 

2、使能evtest用來測試觸摸

Target packages  --->  

Hardware handling  --->   

[*] evtest  

3、使能字庫（后面配置Qt環境變量會用到，否則后面在開發板運行軟件會無法正常顯示字符）

Target packages  ---> 

Fonts, cursors, icons, sounds and themes  --->

[*] DejaVu fonts

[*]   mono fonts (NEW) 

[*]   sans fonts (NEW) 

[*]   serif fonts (NEW) 

[*]   sans condensed fonts (NEW) 

[*]   serif condensed fonts (NEW) 

配置完成后重新make然后接下來使用新編譯的文件系統啟動開發板進行測試。

4.3 測試

4.3.1 屏幕測試

使用modetest測試屏幕顯示。查看該命令使用幫助如下：

# modetest --help

usage: modetest [-acDdefMPpsCvrw]

 Query options:

        -c      list connectors

        -e      list encoders

        -f      list framebuffers

        -p      list CRTCs and planes (pipes)

 Test options:

        -P @:x[++][*][@]  set a plane

        -s [,][@]:[#][-][@]    set a mode

        -C      test hw cursor

        -v      test vsynced page flipping

        -r      set the preferred mode for all connectors

        -w :: set property

        -a      use atomic API

        -F pattern1,pattern2    specify fill patterns

 Generic options:

        -d      drop master after mode set

        -M module       use the given driver

        -D device       use the given device

        Default is to dump all info.

直接執行modetest命令會自動掃描并嘗試打開顯示設備，如下：

# modetest

......

trying to open device 'amdgpu'...failed

trying to open device 'imx-drm'...failed

trying to open device 'virtio_gpu'...failed

......

trying to open device 'stm'...done

Encoders:

id      crtc    type    possible crtcs  possible clones

31      35      DPI     0x00000001      0x00000000

Connectors:

id      encoder status          name            size (mm)       modes   encoders

32      31      connected       DPI-1           117x67          1       31

  modes:

        index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot

  #0 800x480 64.62 800 888 936 976 480 512 515 528 33300 flags: phsync, pvsync; type: preferred, driver

  props:

        1 EDID:

                flags: immutable blob

                blobs:

                value:

        2 DPMS:

                flags: enum

                enums: On=0 Standby=1 Suspend=2 Off=3

                value: 0