OKMX8MM-C开发板只有一个MIPI DSI显示接口，这个接口除了可以连接MIPI显示屏，还可以通过MIPI转LVDS模块，连接LVDS显示屏或HDMI显示屏。
其中MIPI显示屏还分为需要配置和不需要配置的。
1、不需要配置的MIPI屏MIPI接口的显示屏分为需要DSI进入命令模式配置后才能显示的MIPI屏和不需要配置的MIPI屏。不需要配置的MIPI屏比较简单，只要MIPI DSI接口正常输出信号就能正常显示，飞凌嵌入式OKMX8MM-C开发板提供的1024x600分辨率的7寸MIPI屏就是一块不需要配置的MIPI屏，它默认就工作在4lanes高速模式下，只需要将CPU内的显示相关的模块配置好，并让其开始工作，MIPI屏就能够正常显示。
2、需要配置的MIPI屏需要配置的MIPI屏，DSI接口在输出显示信号前需要进入命令模式对显示屏进行配置，配置参数一般由屏体厂家提供。NXP i.MX8MM 评估套件使用的OLED屏RM67191，就是一款需要配置的MIPI显示屏。
3、MIPI转LVDS和HDMI模块这个模块能将MIPI信号转换为LVDS或HDMI信号，通过这个模块可以连接LVDS显示屏或者HDMI显示屏。MIPI转LVDS&HDMI模块需要通过I2C配置转接，将包含对应的显示屏的显示参数等信息配置到芯片内，然后MIPI接口输出对应的显示信号。
二、UBOOT阶段的LOGO显示OKMX8MM-C开发板默认添加了- 1024x600的7寸屏（MIPI7）；
- 自定义7MIPI显示（MIPICUSTOM）；
- MIPI转HDMI的1920x1080 (MIPI2HDMI1920x1080）；
- 1280x720 (MIPI2HDMI1280x720）；
- 640x480 (MIPI2HDMI640x480）；
- 10.1寸1280x800LVDS显示屏（MIPI2HDMI1280x800）；
- 自定义MIPI转LVDS（MIPI2HDMICUSTOM）。
- structdisplay_info_tconst displays[] = {
- {
- .bus = LCDIF_BASE_ADDR,
- .addr = 0,
- .pixfmt = 24,
- .detect = NULL,
- .enable = do_enable_mipi_led,
- .mode = {
- .name = "MIPI7",
- .refresh = 60,
- .xres = 1024,
- .yres = 600,
- .pixclock = 22733, /* 43987200 */
- .left_margin = 48,
- .right_margin = 40,
- .upper_margin = 16,
- .lower_margin = 13,
- .hsync_len = 48,
- .vsync_len = 3,
- .sync = FB_SYNC_EXT,
- .vmode = FB_VMODE_NONINTERLACED
- }
- },
- ...
- {
- .bus = LCDIF_BASE_ADDR,
- .addr = 0,
- .pixfmt = 24,
- .detect = NULL,
- .enable = do_enable_mipi2hdmi,
- .mode = {
- .name = "MIPI2HDMI_1280x720",
- .refresh = 60,
- .xres = 1280,
- .yres = 720,
- .pixclock = 13468, //74250000
- .left_margin = 220,
- .right_margin = 110,
- .upper_margin = 20,
- .lower_margin = 5,
- .hsync_len = 40,
- .vsync_len = 5,
- .sync = FB_SYNC_EXT,
- .vmode = FB_VMODE_NONINTERLACED
- }
- },
- ...
- }
- int board_video_skip(void)
- {
- int i;
- int ret = 0;
- charconst*panel = env_get("panel");
-
- if(!panel) {
- ...
- } else{
- for(i = 0; i < display_count; i++) {
- if(!strcmp(panel, displays.mode.name))
- break;
- }
- }
-
- if(i < display_count) {
- if(!strcmp(panel, "MIPI_CUSTOM") || !strcmp(panel, "MIPI2HDMI_CUSTOM")) {
- charconst* options = env_get("custom_video_mode");
- char*opt = strdup(options);
- get_mode_frome_env(&displays, opt);
- }
- ...
- staticvoid get_mode_frome_env(structdisplay_info_t*dev, char*options)
- {
- char*opt;
- while((opt = strsep(&options, ",")) != NULL) {
- if(!*opt)
- continue;
- if(!strncmp(opt, "xres=", 5)) {
- dev->mode.xres = simple_strtoul(opt + 5, NULL, 0);
- } elseif(!strncmp(opt, "yres=", 5)) {
- dev->mode.yres = simple_strtoul(opt + 5, NULL, 0);
- } elseif(!strncmp(opt, "pixclock=", 9)) {
- dev->mode.pixclock = simple_strtoul(opt + 9, NULL, 0);
- } elseif(!strncmp(opt, "left_margin=", 12)) {
- dev->mode.left_margin = simple_strtoul(opt + 12, NULL, 0);
- } elseif(!strncmp(opt, "right_margin=", 13)) {
- dev->mode.right_margin = simple_strtoul(opt + 13, NULL, 0);
- } elseif(!strncmp(opt, "upper_margin=", 13)) {
- dev->mode.upper_margin = simple_strtoul(opt + 13, NULL, 0);
- } elseif(!strncmp(opt, "lower_margin=", 13)) {
- dev->mode.lower_margin = simple_strtoul(opt + 13, NULL, 0);
- } elseif(!strncmp(opt, "hsync_len=", 10)) {
- dev->mode.hsync_len = simple_strtoul(opt + 10, NULL, 0);
- } elseif(!strncmp(opt, "vsync_len=", 10)) {
- dev->mode.vsync_len = simple_strtoul(opt + 10, NULL, 0);
- } elseif(!strncmp(opt, "sync=", 5)) {
- dev->mode.sync = simple_strtoul(opt + 5, NULL, 0);
- } elseif(!strncmp(opt, "vmode=", 6)) {
- dev->mode.vmode = simple_strtoul(opt + 6, NULL, 0);
- } elseif(!strncmp(opt, "refresh=", 8)) {
- dev->mode.refresh = simple_strtoul(opt + 8, NULL, 0);
- }
- }
- printf("use custom mode %s: %d, %d, %d, %d, %d, %d, %d, %d, %d, %d, %08X, %08X \n ", \
- dev->mode.name,dev->mode.refresh, dev->mode.xres, dev->mode.yres, dev->mode.pixclock, \
- dev->mode.left_margin, dev->mode.right_margin, dev->mode.upper_margin, dev->mode.lower_margin, \
- dev->mode.hsync_len, dev->mode.vsync_len, dev->mode.sync, dev->mode.vmode);
-
- }
MIPI转LVDS和HDMI模块，能够正常显示的条件是：
- 显示结构体内配置当前显示屏的显示参数；
- I2C下发正确的配置参数到转接模块。
- ...
- u-boot=> setenv panel MIPI2HDMI_CUSTOM
- u-boot=> setenv custom_video_mode xres=1024,yres=768
- u-boot=> sa
- SavingEnvironment to MMC... Writing to MMC(1)... OK
- u-boot=> reset
- resetting ...
- ...
- LoadingEnvironment from MMC... OK
- use custom mode MIPI2HDMI_CUSTOM: 60, 1024, 768, 12048, 200, 64, 24, 1, 136, 3, 00000004, 00000000
- ...
- ...
- u-boot=> setenv panel MIPI_CUSTOM
- u-boot=> setenv custom_video_mode xres=800,yres=600,pixclock=20000,refresh=55
- u-boot=> sa
- SavingEnvironment to MMC... Writing to MMC(1)... OK
- u-boot=> reset
- resetting ...
- ...
- LoadingEnvironment from MMC... OK
- use custom mode MIPI_CUSTOM: 55, 800, 600, 20000, 48, 40, 16, 13, 48, 3, 00000004, 00000000
- Display: MIPI_CUSTOM (800x600)
- Video: 800x600x24
- ...
这种显示屏对比不需配置的MIPI显示屏多了一步配置，可以参照原厂提供的RM67191进行修改。
首先，添加一组显示参数，显示参数根据显示屏修改，修改文件board/freescale/imx8mmevk/imx8mmevk.c。
- {
- .bus = LCDIF_BASE_ADDR,
- .addr = 0,
- .pixfmt = 24,
- .detect = NULL,
- .enable = do_enable_mipi_led,
- .mode = {
- .name = "RM67191_OLED",
- .refresh = 60,
- .xres = 1080,
- .yres = 1920,
- .pixclock = 7575, /* 132000000 */
- .left_margin = 34,
- .right_margin = 20,
- .upper_margin = 4,
- .lower_margin = 10,
- .hsync_len = 2,
- .vsync_len = 2,
- .sync = FB_SYNC_EXT,
- .vmode = FB_VMODE_NONINTERLACED
- }
- }
然后修改这组参数的使能函数
- void do_enable_mipi_led(structdisplay_info_tconst*dev)
- {
- imx_iomux_v3_setup_multiple_pads(backlight_pads,
- ARRAY_SIZE(backlight_pads));
-
- gpio_request(IMX_GPIO_NR(1, 1), "backlight");
- gpio_direction_output(IMX_GPIO_NR(1, 1), 0);
-
- gpio_request(IMX_GPIO_NR(1, 8), "DSI EN");
- gpio_direction_output(IMX_GPIO_NR(1, 8), 0);
- mdelay(10);
- gpio_direction_output(IMX_GPIO_NR(1, 8), 1);
-
- /* enable the dispmix & mipi phy power domain */
- call_imx_sip(FSL_SIP_GPC, FSL_SIP_CONFIG_GPC_PM_DOMAIN, DISPMIX, true, 0);
- call_imx_sip(FSL_SIP_GPC, FSL_SIP_CONFIG_GPC_PM_DOMAIN, MIPI, true, 0);
-
- /* Put lcdif out of reset */
- disp_mix_bus_rstn_reset(imx8mm_mipi_dsim_plat_data.gpr_base, false);
- disp_mix_lcdif_clks_enable(imx8mm_mipi_dsim_plat_data.gpr_base, true);
-
- /* Setup mipi dsim */
- sec_mipi_dsim_setup(&imx8mm_mipi_dsim_plat_data);
- rm67191_init();
- rm67191_dev.name = dev->mode.name;
- imx_mipi_dsi_bridge_attach(&rm67191_dev); /* attach rm67191 device */
- }
- struct mipi_dsi_client_dev rm67191_dev = {
- .channel = 0,
- .lanes = 4,
- .format = MIPI_DSI_FMT_RGB888,
- .mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_SYNC_PULSE |
- MIPI_DSI_MODE_EOT_PACKET | MIPI_DSI_MODE_VIDEO_HSE,
- };
修改显示屏驱动drivers/video/rm67191.c，在函数int rm67191lcdsetup(struct mipidsiclientdev *paneldev)添加自己的屏的初始化序列。
修改完成后编译测试。
注意:uboot代码不开源，修改代码需要联系销售人员
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