本文章為《STM32MP157 Linux系統(tǒng)移植開發(fā)篇》系列中的一篇，筆者使用的開發(fā)平臺(tái)為華清遠(yuǎn)見FS-MP1A開發(fā)板（STM32MP157開發(fā)板）。stm32mp157是ARM雙核，2個(gè)A7核，1個(gè)M4核，A7核上可以跑Linux操作系統(tǒng)，M4核上可以跑FreeRTOS、RT-Thread等實(shí)時(shí)操作系統(tǒng)，STM32MP157開發(fā)板所以既可以學(xué)嵌入式linux，也可以學(xué)stm32單片機(jī)。

針對(duì)FS-MP1A開發(fā)板，除了Linux系統(tǒng)移植篇外，還包括其他多系列教程，包括Cortex-A7開發(fā)篇、Cortex-M4開發(fā)篇、擴(kuò)展板驅(qū)動(dòng)移植篇、Linux應(yīng)用開發(fā)篇、FreeRTOS系統(tǒng)移植篇、Linux驅(qū)動(dòng)開發(fā)篇、硬件設(shè)計(jì)篇、人工智能機(jī)器視覺篇、Qt應(yīng)用編程篇、Qt綜合項(xiàng)目實(shí)戰(zhàn)篇等。歡迎關(guān)注，更多stm32mp157開發(fā)教程及視頻，可加技術(shù)交流Q群459754978，感謝關(guān)注。

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1.實(shí)驗(yàn)原理

DSI(Display Serial Interface)，是有MIPI聯(lián)盟定義的一組通信協(xié)議的一部分，MIPI DSI主機(jī)控制器是一個(gè)數(shù)字核心，實(shí)現(xiàn)MIPI DSI規(guī)范中定義的所有協(xié)議功能。它提供了系統(tǒng)和MIPI D_PHY中間的接口，允許用戶和符合DSI的顯示器進(jìn)行通信。STM32MP157A系列芯片集成MIPI DSI主機(jī)控制器。

MIPI?DSI主機(jī)包括內(nèi)部連接到LTDC的專用視頻接口以及一個(gè)通用的APB接口，可用于向顯示器傳輸信息。

FS-MP1A提供兩組LCD顯示接口，分別是RGB和MIPI接口，本節(jié)介紹如何在Linux中完成MIPI LCD的支持。

上圖為MIPI LCD的接口，接口信號(hào)線分為兩組，分別是由DSI_D0P、DSI_D0N、DSI_D1P、DSI_D1N、DSI_CKP、DSI_CKN、DSI_TE、DSI_RST、LCD_PWM組成的LCD接口和由I2C2_SCL、I2C2_SDA、TP_RST、TP_IRQ組成的觸摸屏接口，本節(jié)介紹LCD的支持。

DSI_D0P、DSI_D0N、DSI_D1P、DSI_D1N、DSI_CKP、DSI_CKN是DSI-MIPI的信號(hào)線，DSI_TE未使用，DSI_RST是LCD屏復(fù)位信號(hào)LCD_PWM是背光控制信號(hào)。

MIPI LCD接口管腳對(duì)應(yīng)關(guān)系：

原理圖網(wǎng)絡(luò)編號(hào)對(duì)應(yīng)管腳管腳功能管腳功能碼DSI_D0PDSI_D0PDSI_D0PDSI信號(hào)線對(duì)應(yīng)管腳為單一功能管腳DSI_D0NDSI_D0NDSI_D0NDSI_D1PDSI_D1PDSI_D1PDSI_D1NDSI_D1NDSI_D1NDSI_CKPDSI_CKPDSI_CKPDSI_CKNDSI_CKNDSI_CKNDSI_TEPC6IODSI_RSTPG9IOLCD_PWMPA5TIM2_CH1AF1

1. PWM設(shè)備節(jié)點(diǎn)

參考文檔：

Documentation/devicetree/bindings/pwm/pwm-stm32.txt

內(nèi)核中ST對(duì)STM32MP15x系列芯片的設(shè)備樹資源了做了定義，可參見：

arch/arm/boot/dts/stm32mp151.dtsi

stm32mp151中timers2定義如下：

timers2: timer@40000000 {

#address-cells = <1>;

#size-cells = <0>;

compatible = "st,stm32-timers";

reg = <0x40000000 0x400>;

clocks = <&rcc TIM2_K>;

clock-names = "int";

dmas = <&dmamux1 18 0x400 0x80000001>,

<&dmamux1 19 0x400 0x80000001>,

<&dmamux1 20 0x400 0x80000001>,

<&dmamux1 21 0x400 0x80000001>,

<&dmamux1 22 0x400 0x80000001>;

dma-names = "ch1", "ch2", "ch3", "ch4", "up";

status = "disabled";

pwm {

compatible = "st,stm32-pwm";

#pwm-cells = <3>;

status = "disabled";

};

timer@1 {

compatible = "st,stm32h7-timer-trigger";

reg = <1>;

status = "disabled";

};

counter {

compatible = "st,stm32-timer-counter";

status = "disabled";

};

};

上述代碼只對(duì)timers5做了基本的初始化，并沒有針對(duì)不同的硬件設(shè)計(jì)做適配，所以需結(jié)合硬件補(bǔ)全設(shè)備樹節(jié)點(diǎn)信息。

參考文檔或stm32mp15xx-dkx.dtsi對(duì)于i2c設(shè)備節(jié)點(diǎn)的描述，增加timers內(nèi)容如下：

&timers2 {

/* spare dmas for other usage */

/delete-property/dmas;

/delete-property/dma-names;

status = "okay";

pwm2: pwm {

pinctrl-0 = <&pwm2_pins_b>;

pinctrl-1 = <&pwm2_sleep_pins_b>;

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

#pwm-cells = <2>;

status = "okay";

};

timer@2 {

status = "disabled";

};

};

stm32mp15-pinctrl.dtsi對(duì)于pwm2的描述與FS-MP1A所使用管腳不一致，所以無(wú)法直接使用，需參考其增加如下內(nèi)容：

pwm2_pins_b: pwm2-0 {

pins {

pinmux = <STM32_PINMUX('A', 5, AF1)>; /* TIM2_CH1 */

bias-pull-down;

drive-push-pull;

slew-rate = <0>;

};

};

pwm2_sleep_pins_b: pwm1-sleep-0 {

pins {

pinmux = <STM32_PINMUX('A', 5, ANALOG)>; /* TIM2_CH1 */

};

};

1. 背光設(shè)備節(jié)點(diǎn)

參考文檔：

Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt

Documentation/devicetree/bindings/leds/backlight/gpio-backlight.txt

FS-MP1A背光可以通過(guò)GPIO驅(qū)動(dòng)也可通過(guò)PWM2的通道1驅(qū)動(dòng)，可以對(duì)比參考文檔或內(nèi)核中其他設(shè)備樹關(guān)于背光的定義。

GPIO驅(qū)動(dòng)背光節(jié)點(diǎn)內(nèi)容如下：

panel_backlight: panel-backlight {

compatible = "gpio-backlight";

gpios = <&gpiod 13 GPIO_ACTIVE_LOW>;

default-on;

status = "okay";

};

PWM驅(qū)動(dòng)背光節(jié)點(diǎn)內(nèi)容如下：

panel_backlight: panel-backlight {

compatible = "pwm-backlight";

pwms = <&pwm2 0 5000000>;

brightness-levels = <0 4 8 16 32 64 128 255>;

default-brightness-level = <6>;

status = "okay";

};

1. LTDC設(shè)備節(jié)點(diǎn)

參考文檔：

Documentation/devicetree/bindings/display/st,stm32-ltdc.txt

由于前面章節(jié)已經(jīng)對(duì)LTDC做了講解，并且已經(jīng)增加了LTDC的設(shè)備節(jié)點(diǎn)，本節(jié)只需在原有基礎(chǔ)上增加DSI對(duì)應(yīng)的數(shù)據(jù)通道即可。

&ltdc {

status = "okay";

port {

#address-cells = <1>;

#size-cells = <0>;

ltdc_ep1_out: endpoint@1 {

reg = <1>;

remote-endpoint = <&dsi_in>;

};

};

};

1. Panel設(shè)備樹節(jié)點(diǎn)

參考文檔

Documentation/devicetree/bindings/display/panel/panel-dsi-cm.txt

結(jié)合參考文檔及內(nèi)核中STM32MP157其他設(shè)備樹文件，Panel設(shè)備樹節(jié)點(diǎn)為：

panel: panel@0 {

compatible = "sitronix,st7701";

reg = <0>;

reset-gpios = <&gpiog 9 GPIO_ACTIVE_HIGH>;

power-supply = <&v3v3>;

status = "okay";

port {

panel_in: endpoint {

remote-endpoint = <&dsi_out>;

};

};

};

1. DSI設(shè)備樹節(jié)點(diǎn)

參考文檔：

Documentation/devicetree/bindings/display/mipi-dsi-bus.txt

內(nèi)核中ST對(duì)STM32MP15x系列芯片的設(shè)備樹資源了做了定義，可參見：

arch/arm/boot/dts/stm32mp157.dtsi

stm32mp157中dsi定義如下：

dsi: dsi@5a000000 {

compatible = "st,stm32-dsi";

reg = <0x5a000000 0x800>;

phy-dsi-supply = <&reg18>;

clocks = <&rcc DSI_K>, <&scmi0_clk CK_SCMI0_HSE>, <&rcc DSI_PX>;

clock-names = "pclk", "ref", "px_clk";

resets = <&rcc DSI_R>;

reset-names = "apb";

status = "disabled";

};

上述代碼只對(duì)dsi做了基本的初始化，并沒有針對(duì)不同的硬件設(shè)計(jì)做適配，所以需結(jié)合硬件補(bǔ)全設(shè)備樹節(jié)點(diǎn)信息。補(bǔ)齊后內(nèi)容如下：

&dsi {

#address-cells = <1>;

#size-cells = <0>;

status = "okay";

ports {

#address-cells = <1>;

#size-cells = <0>;

port@0 {

reg = <0>;

dsi_in: endpoint {

remote-endpoint = <&ltdc_ep1_out>;

};

};

port@1 {

reg = <1>;

dsi_out: endpoint {

remote-endpoint = <&dsi_panel_in>;

};

};

};

panel_dsi: panel-dsi@0 {

compatible = "sitronix,st7701";

reg = <0>;

reset-gpios = <&gpiog 9 GPIO_ACTIVE_LOW>;

backlight = <&panel_backlight>;

power-supply = <&v3v3>;

status = "okay";

port {

dsi_panel_in: endpoint {

remote-endpoint = <&dsi_out>;

};

};

};

};

2.實(shí)驗(yàn)?zāi)康?/h1>

熟悉基于Linux操作系統(tǒng)下的MIPI-LCD設(shè)備驅(qū)動(dòng)移植配置過(guò)程。

3.實(shí)驗(yàn)平臺(tái)

華清遠(yuǎn)見開發(fā)環(huán)境，F(xiàn)S-MP1A平臺(tái)；

4.實(shí)驗(yàn)步驟

1. 導(dǎo)入交叉編譯工具鏈

linux@ubuntu:$ source /opt/st/stm32mp1/3.1-openstlinux-5.4-dunfell-mp1-20-06-24/environment-setup-cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi

1. 添加MIPI-LCD驅(qū)動(dòng)

FS-MP1A配套MIPI屏幕主控芯片是st7701，內(nèi)核中并沒有提供其的驅(qū)動(dòng)，所以需要移植st7701的驅(qū)動(dòng)

將【華清遠(yuǎn)見-FS-MP1A開發(fā)資料\02-程序源碼\04-Linux系統(tǒng)移植\04-移植相關(guān)文件\02-Linux內(nèi)核移植\st7701驅(qū)動(dòng)】下的panel-sitronix-st7701.c復(fù)制到內(nèi)核源碼下的drivers/gpu/drm/panel/目錄下。

linux@ubuntu $> cp panel-sitronix-st7701.c drivers/gpu/drm/panel/

1. 添加pwm2內(nèi)容

修改stm32mp15xx-fsmp1x.dtsi，在stm32mp15xx-fsmp1x.dtsi文件末尾添加如下內(nèi)容：

&timers2 {

/* spare dmas for other usage */

/delete-property/dmas;

/delete-property/dma-names;

status = "okay";

pwm2: pwm {

pinctrl-0 = <&pwm2_pins_b>;

pinctrl-1 = <&pwm2_sleep_pins_b>;

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

#pwm-cells = <2>;

status = "okay";

};

timer@2 {

status = "disabled";

};

};

&pinctrl {

pwm2_pins_b: pwm2-0 {

pins {

pinmux = <STM32_PINMUX('A', 5, AF1)>; /* TIM2_CH1 */

bias-pull-down;

drive-push-pull;

slew-rate = <0>;

};

};

pwm2_sleep_pins_b: pwm1-sleep-0 {

pins {

pinmux = <STM32_PINMUX('A', 5, ANALOG)>; /* TIM2_CH1 */

};

};

};

1. 添加背光內(nèi)容

修改stm32mp15xx-fsmp1x.dtsi，在根節(jié)點(diǎn)中添加如下內(nèi)容：

panel_backlight: panel-backlight {

compatible = "pwm-backlight";

pwms = <&pwm2 0 5000000>;

brightness-levels = <0 4 8 16 32 64 128 255>;

default-brightness-level = <6>;

status = "okay";

};

1. 增加設(shè)備樹文件

由于MIPI LCD并非FS-MP1A必須配置，本節(jié)增加一個(gè)設(shè)備樹文件，對(duì)應(yīng)增加了屏幕的設(shè)備。

在內(nèi)核的arch/arm/boot/dts目錄下新建文件stm32mp157a-fsmp1a-mipi050.dts文件并添加如下內(nèi)容：

#include "stm32mp157a-fsmp1a.dts"

/ {

model = "HQYJ STM32MP157 FSMP1A MIPI Discovery Board";

compatible = "st,stm32mp157a-dk1", "st,stm32mp157";

};

由于增加了新的設(shè)備樹文件需修改arch/arm/boot/dts/Makefile，在文件中增加新的條目，紅色字體部分為增加內(nèi)容

dtb-$(CONFIG_ARCH_STM32) += \

…..

stm32mp157a-dk1.dtb \

stm32mp157a-fsmp1a.dtb \

stm32mp157a-fsmp1a-mipi050.dtb \

stm32mp157d-dk1.dtb \

1. 添加ltdc內(nèi)容

修改stm32mp157a-fsmp1a-mipi050.dts，在文件末尾添加如下內(nèi)容：

&ltdc {

status = "okay";

port {

#address-cells = <1>;

#size-cells = <0>;

ltdc_ep1_out: endpoint@1 {

reg = <1>;

remote-endpoint = <&dsi_in>;

};

};

};

1. 添加dts內(nèi)容

修改stm32mp157a-fsmp1a-mipi050.dts，在文件末尾添加如下內(nèi)容：

&dsi {

#address-cells = <1>;

#size-cells = <0>;

status = "okay";

ports {

#address-cells = <1>;

#size-cells = <0>;

port@0 {

reg = <0>;

dsi_in: endpoint {

remote-endpoint = <&ltdc_ep1_out>;

};

};

port@1 {

reg = <1>;

dsi_out: endpoint {

remote-endpoint = <&dsi_panel_in>;

};

};

};

panel_dsi: panel-dsi@0 {

compatible = "sitronix,st7701";

reg = <0>;

reset-gpios = <&gpiog 9 GPIO_ACTIVE_HIGH>;

power-supply = <&v3v3>;

status = "okay";

port {

dsi_panel_in: endpoint {

remote-endpoint = <&dsi_out>;

};

};

};

};

1. 配置內(nèi)核

配置內(nèi)核支持st7701，并列出主要選項(xiàng)，如下：

linux@ubuntu:$ make menuconfig

Device Drivers --->

Graphics support --->

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

<*> DRM Support for STMicroelectronics SoC Series

<*> STMicroelectronics specific extensions for Synopsys MIPI DSI

Display Panels --->

<*> Sitronix ST7701 panel driver

Backlight & LCD device support --->

<*> Generic PWM based Backlight Driver

<*> Generic GPIO based Backlight Driver

1. 增加啟動(dòng)項(xiàng)

在虛擬機(jī)/tftpboot /tftpboot/pxelinux.cfg/01-00-80-e1-42-60-17末尾添加

LABEL stm32mp157a-fsmp1a-mipi
KERNEL /uImage
FDT /stm32mp157a-fsmp1a-mipi050.dtb
APPEND root=/dev/mmcblk1p4 rootwait rw console=ttySTM0,115200

1. 編譯內(nèi)核及設(shè)備樹

linux@ubuntu:$ make -j4 uImage dtbs LOADADDR=0xC2000040

1. 重啟測(cè)試

將編譯好的設(shè)備樹和內(nèi)核鏡像拷貝到/tftpboot目錄下，通過(guò)tftp引導(dǎo)內(nèi)核，設(shè)備連接HDMI顯示器，重啟設(shè)備后查看/sys/class/drm會(huì)多出HMID的信息，同時(shí)顯示器會(huì)有顯示。

硬件平臺(tái)：華清遠(yuǎn)見FS-MP1A開發(fā)板（STM32MP157）

部分開發(fā)教程下載：加QQ群459754978，群文件里有。

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