一、整體流程概述

首先從aboot_init開始，去走LCD的初始化流程，在aboot中判斷是哪種存儲方式和啓動方式，然後進入LCD在LK的唯一初始化入口——target_display_init。然後會調用對應的gcdb_display_init方法。判斷是哪個屏，並初始化對應的參數，以及對其進行上電，最終點亮屏幕。與此同時在點亮之後，會在aboot中將對應的屏幕信息寫入到pbuf中，以便kernel能夠獲取到對應的屏幕信息，然後加載參數並點亮。如下是簡單的流程圖：

二、詳細流程分析

1、LK中LCD的唯一入口

首先我們從aboot_init方法開始，看如何一步步啓動LCD：

void aboot_init(const struct app_descriptor *app)
{
    ... ...
    target_display_init(device.display_panel);
    ... ...
}

aboot中省略了系統系統的前期準備以及相關的啓動模式，這部分後續文章在進行分析，當前繼續分析LCD啓動相關。

這裏就可以看到我們的入口方法：target_display_init()。

target_display_init()

根據不同的平臺，此處調用的target_display_init()也是不同的，我們以MSM8909爲例。此處調用的是msm8909目錄下的Target_display.c文件。我們開始看下target_display_init()的調用流程：

void target_display_init(const char *panel_name)
{
	... ...

	if (target_splash_disable())//如果splash_disable的宏開啓，則LK階段不再初始化LCD，參數等的初始化均在kernel階段進行
		return;

	do {
		target_force_cont_splash_disable(false);
		ret = gcdb_display_init(oem.panel, MDP_REV_305, MIPI_FB_ADDR);
		if (!ret || ret == ERR_NOT_SUPPORTED) {
			break;
		} else {
			target_force_cont_splash_disable(true);
			msm_display_off();
		}
	} while (++panel_loop <= oem_panel_max_auto_detect_panels());

	... ...
}

gcdb_display_init()

target_display_init方法中最關鍵的部分即do...while結構。這裏會對LCD繼續做初始化，即gcdb_display_init方法。該方法在gcdb_display.c (bootable\bootloader\lk\dev\gcdb\display)，我們先來看下該方法的實現：

int gcdb_display_init(const char *panel_name, uint32_t rev, void *base)
{
	int ret = NO_ERROR;
	int pan_type;

	dsi_video_mode_phy_db.pll_type = DSI_PLL_TYPE_28NM;

        //通過讀取對應的ID或者mipi回讀判斷是哪塊屏，並將屏幕信息保存在pinfo結構體中
	pan_type = oem_panel_select(panel_name, &panelstruct, &(panel.panel_info),
				 &dsi_video_mode_phy_db);

	if (pan_type == PANEL_TYPE_DSI) {
		if (update_dsi_display_config())
			goto error_gcdb_display_init;
		target_dsi_phy_config(&dsi_video_mode_phy_db);
		mdss_dsi_check_swap_status();
		mdss_dsi_set_pll_src();
		if (dsi_panel_init(&(panel.panel_info), &panelstruct)) {
			dprintf(CRITICAL, "DSI panel init failed!\n");
			ret = ERROR;
			goto error_gcdb_display_init;
		}

		panel.panel_info.mipi.mdss_dsi_phy_db = &dsi_video_mode_phy_db;
		panel.pll_clk_func = mdss_dsi_panel_clock;
		panel.dfps_func = mdss_dsi_mipi_dfps_config;
		panel.power_func = mdss_dsi_panel_power;
		panel.pre_init_func = mdss_dsi_panel_pre_init;
		panel.bl_func = mdss_dsi_bl_enable;
		panel.dsi2HDMI_config = mdss_dsi2HDMI_config;
		/*
		 * Reserve fb memory to store pll codes and pass
		 * pll codes values to kernel.
		 */
		panel.panel_info.dfps.dfps_fb_base = base;
		base += DFPS_PLL_CODES_SIZE;
		panel.fb.base = base;
		dprintf(SPEW, "dfps base=0x%p,d, fb_base=0x%p!\n",
				panel.panel_info.dfps.dfps_fb_base, base);

		panel.fb.width =  panel.panel_info.xres;
		panel.fb.height =  panel.panel_info.yres;
		panel.fb.stride =  panel.panel_info.xres;
		panel.fb.bpp =  panel.panel_info.bpp;
		panel.fb.format = panel.panel_info.mipi.dst_format;
	} else if (pan_type == PANEL_TYPE_EDP) {
		mdss_edp_panel_init(&(panel.panel_info));
		/* prepare func is set up at edp_panel_init */
                panel.clk_func = mdss_edp_panel_clock;
                panel.power_func = mdss_edp_panel_power;
		panel.bl_func = mdss_edp_bl_enable;
                panel.fb.format = FB_FORMAT_RGB888;
	} else {
		dprintf(CRITICAL, "Target panel init not found!\n");
		ret = ERR_NOT_SUPPORTED;
		goto error_gcdb_display_init;
	}

	panel.fb.base = base;
	panel.mdp_rev = rev;

        //通過獲取到的屏幕信息繼續進行初始化
	ret = msm_display_init(&panel);

error_gcdb_display_init:
	display_enable = ret ? 0 : 1;
	return ret;
}

可以看到該方法主要有四個動作：

① 選取對應的屏幕：dsi_panel_init()

pan_type = oem_panel_select(panel_name, &panelstruct, &(panel.panel_info),
&dsi_video_mode_phy_db);

② 將初始化信息保存在pinfo中：dsi_panel_init()

dsi_panel_init(&(panel.panel_info), &panelstruct)

③ 根據panel type初始化panel結構體

④ 根據上述信息進一步初始化LCD：msm_display_init()

ret = msm_display_init(&panel);

2、屏幕識別&獲取初始化參數信息

oem_panel_select()

該方法同樣根據平臺不同會各自選取對應的執行文件，我們同樣使用MSM8909對應的Oem_panel.c。此方法會根據硬件ID或者回讀MIPI的方法來識別不同的屏。然後將識別到的屏幕信息保存在panelstruct結構體中。

int oem_panel_select(const char *panel_name, struct panel_struct *panelstruct,
			struct msm_panel_info *pinfo,
			struct mdss_dsi_phy_ctrl *phy_db)
{
	uint32_t hw_id = board_hardware_id();
	uint32_t platform_subtype = board_hardware_subtype();
	int32_t panel_override_id;

	if (panel_name) {
		panel_override_id = panel_name_to_id(supp_panels,
				ARRAY_SIZE(supp_panels), panel_name);

		if (panel_override_id < 0) {
			dprintf(CRITICAL, "Not able to search the panel:%s\n",
					 panel_name);
		} else if (panel_override_id < UNKNOWN_PANEL) {
			/* panel override using fastboot oem command */
			panel_id = panel_override_id;

			dprintf(INFO, "OEM panel override:%s\n",
					panel_name);
			goto panel_init;
		}
	}

    if((panel_id=switch_panel_id())==UNKNOWN_PANEL)//獲取屏幕ID
    {
		return PANEL_TYPE_UNKNOWN;
	}
	  special_panel = panel_id;

panel_init:
	phy_db->regulator_mode = DSI_PHY_REGULATOR_LDO_MODE;
	return init_panel_data(panelstruct, pinfo, phy_db);//獲取配置參數
}

① 首先我們來看下如何識別不同的LCD：switch_panel_id()

/*
* switch panel id by id0 and id1
*/
int switch_panel_id(void)
{
      int lcd_id0;
      int lcd_id1;

	gpio_tlmm_config(panel_id0.pin_id, 0,
				panel_id0.pin_direction, panel_id0.pin_pull,
				panel_id0.pin_strength, panel_id0.pin_state);

	gpio_tlmm_config(panel_id1.pin_id, 0,
				panel_id1.pin_direction, panel_id1.pin_pull,
				panel_id1.pin_strength, panel_id1.pin_state);
	//mdelay(10);
	lcd_id1=1;
	lcd_id0=1;
	lcd_id1=gpio_status(panel_id1.pin_id);//獲取gpio狀態
	lcd_id0=gpio_status(panel_id0.pin_id);

	dprintf(INFO,"lancelot lcd_id0=%d.\n",lcd_id0);
	dprintf(INFO,"lancelot lcd_id1=%d.\n",lcd_id1);
	if((lcd_id1 == 1)&&(lcd_id0 == 0)){
		return JD9365_STARRY_VIDEO_PANEL;
	}else{
		return NT35521Z_INX101_VIDEO_PANEL;
	}
}

此處給出的是通過兩個硬件ID腳的狀態組合進行識別的。即ID0和ID1。分別有高、低兩種狀態。兩個ID腳的組合可以實現四種狀態（00,01,10,11），也就是說我們足夠識別四種屏。當然硬件上首先要能夠進行區分。

② 區分panel id後，我們就可以根據panel id獲取不同的配置參數信息：init_panel_data()

static int init_panel_data(struct panel_struct *panelstruct,
			struct msm_panel_info *pinfo,
			struct mdss_dsi_phy_ctrl *phy_db)
{
	int pan_type = PANEL_TYPE_DSI;//panel type

	switch (panel_id) {
    ... ...
    case NT35521Z_INX101_VIDEO_PANEL:
		panelstruct->paneldata    = &nt35521z_inx101_video_panel_data;
        panelstruct->panelres     = &nt35521z_inx101_video_panel_res;
        panelstruct->color                = &nt35521z_inx101_video_color ;
        panelstruct->videopanel   = &nt35521z_inx101_video_video_panel ;
        panelstruct->commandpanel = &nt35521z_inx101_video_command_panel  ;
        panelstruct->state                = &nt35521z_inx101_video_state;
        panelstruct->laneconfig   = &nt35521z_inx101_video_lane_config;
        panelstruct->paneltiminginfo
                    = &nt35521z_inx101_video_timing_info;
        panelstruct->panelresetseq
                    = &nt35521z_inx101_video_reset_seq;
        panelstruct->backlightinfo = &nt35521z_inx101_video_backlight;
        pinfo->mipi.panel_on_cmds
                    =  nt35521z_inx101_video_on_command;
        pinfo->mipi.num_of_panel_on_cmds
                    = NT35521Z_INX101_VIDEO_ON_COMMAND;
        pinfo->mipi.panel_off_cmds
					= nt35521z_inx101_video_off_command;
		pinfo->mipi.num_of_panel_off_cmds
					= NT35521Z_INX101_VIDEO_OFF_COMMAND;
        memcpy(phy_db->timing,
                    nt35521z_inx101_video_timings, TIMING_SIZE);
        break;
	... ...
	}
	return pan_type;
}

init_panel_data()初始化panel數據，主要初始化panel_struct結構體數據，然後返回panel類型PANEL_TYPE_DSI（還有EDP和HDMI格式）。據對應的panel_id值將對應的屏幕參數賦值給panelstruct結構體。此結構體對應/dsi-panel-xxx-video.dtsi文件，此結構體主要成員如下：

struct panel_struct {
	struct panel_config         *paneldata;//基本參數信息
	struct panel_resolution     *panelres;//Panel的分辨率、時序參數、極性等數據
	struct color_info           *color;
	struct videopanel_info      *videopanel;
	struct commandpanel_info    *commandpanel;
	struct command_state        *state;
	struct lane_configuration   *laneconfig;//這裏可看出只支持到4lane，支持的lane對應的state爲1，否則爲0
	struct panel_timing         *paneltiminginfo;
	struct panel_reset_sequence *panelresetseq;//對應設備樹文件的qcom,mdss-dsi-reset-sequence =<1 20>, <0 20>, <1 20>;這裏可讓pin狀態及演示多久後再修改pin狀態。
	struct backlight            *backlightinfo;
	struct fb_compression	    fbcinfo;
	struct topology_config	    *config;
};

struct backlight {
	uint16_t bl_interface_type; //背光控制方式
	uint16_t bl_min_level;//背光最小值
	uint16_t bl_max_level;//背光最大值
	uint16_t bl_step;//間隔值
	uint16_t bl_pmic_controltype;
	char     *bl_pmic_model;
};

dsi_panel_init

panel_display.c (bootable\bootloader\lk\dev\gcdb\display)

根據panel_info和panelstruct將對應屏幕的參數初始化到pinfo中。

int dsi_panel_init(struct msm_panel_info *pinfo,
			struct panel_struct *pstruct)
{
	int ret = NO_ERROR;
	/* Resolution setting*/
	pinfo->xres = pstruct->panelres->panel_width;
	pinfo->yres = pstruct->panelres->panel_height;
	pinfo->lcdc.h_back_porch = pstruct->panelres->hback_porch;
	pinfo->lcdc.h_front_porch = pstruct->panelres->hfront_porch;
	pinfo->lcdc.h_pulse_width = pstruct->panelres->hpulse_width;
	pinfo->lcdc.v_back_porch = pstruct->panelres->vback_porch;
	pinfo->lcdc.v_front_porch = pstruct->panelres->vfront_porch;
	pinfo->lcdc.v_pulse_width = pstruct->panelres->vpulse_width;
	pinfo->lcdc.hsync_skew = pstruct->panelres->hsync_skew;

	pinfo->border_top = pstruct->panelres->vtop_border;
	pinfo->border_bottom = pstruct->panelres->vbottom_border;
	pinfo->border_left = pstruct->panelres->hleft_border;
	pinfo->border_right = pstruct->panelres->hright_border;
    ... ...
}

初始化panel結構體

初始化panel全局變量的其他結構體成員

                panel.panel_info.mipi.mdss_dsi_phy_db = &dsi_video_mode_phy_db;
		panel.pll_clk_func = mdss_dsi_panel_clock;
		panel.dfps_func = mdss_dsi_mipi_dfps_config;
		panel.power_func = mdss_dsi_panel_power;
		panel.pre_init_func = mdss_dsi_panel_pre_init;
		panel.bl_func = mdss_dsi_bl_enable;
		panel.dsi2HDMI_config = mdss_dsi2HDMI_config;
		/*
		 * Reserve fb memory to store pll codes and pass
		 * pll codes values to kernel.
		 */
		panel.panel_info.dfps.dfps_fb_base = base;
		base += DFPS_PLL_CODES_SIZE;
		panel.fb.base = base;
		dprintf(SPEW, "dfps base=0x%p,d, fb_base=0x%p!\n",
				panel.panel_info.dfps.dfps_fb_base, base);

		panel.fb.width =  panel.panel_info.xres;
		panel.fb.height =  panel.panel_info.yres;
		panel.fb.stride =  panel.panel_info.xres;
		panel.fb.bpp =  panel.panel_info.bpp;
		panel.fb.format = panel.panel_info.mipi.dst_format;

3、屏幕進一步初始化及點亮

獲取到對應的屏幕信息以及參數後，會調用msm_display_init方法，進一步的爲屏幕的點亮做初始化的動作。實際在該方法中就開始對屏幕進行上電、第一幀顯示動畫、背光燈的進行控制。

int msm_display_init(struct msm_fb_panel_data *pdata)
{
	int ret = NO_ERROR;
        ... ...
	/* Turn on panel 給panel上電*/
	if (pdata->power_func)
		ret = pdata->power_func(1, &(panel->panel_info));
        ... ...
	/* Enable clock 使能CLK*/
	if (pdata->clk_func)
		ret = pdata->clk_func(1, &(panel->panel_info));
        ... ...
        //調用calculate_clock_config(pinfo)計算時鐘配置和調用target_panel_clock(enable, pinfo)配置目標panel的時鐘。
	if (pdata->pll_clk_func)
		ret = pdata->pll_clk_func(1, &(panel->panel_info));
        ... ...
        //爲幀緩衝器(frame buffer)分配內存。
	ret = msm_fb_alloc(&(panel->fb));
	if (ret)
		goto msm_display_init_out;

	fbcon_setup(&(panel->fb));
	display_image_on_screen();//調用fetch_image_from_partition()從splash分區獲取lk logo圖片，如果splash分區沒有滿足要求的數據，就顯示默認的logo。
        ... ...

	ret = msm_display_config();//根據pinfo->type，比如我們這裏是MIPI_VIDEO_PANEL來配置msm平臺display，配置時還需要根據MDP(MobileDisplay processor)的版本來調用對應的config函數
	if (ret)
		goto msm_display_init_out;

	ret = msm_display_on();
	if (ret)
		goto msm_display_init_out;

	if (pdata->post_power_func)
		ret = pdata->post_power_func(1);
	if (ret)
		goto msm_display_init_out;

	/* Turn on backlight */
	if (pdata->bl_func)
		ret = pdata->bl_func(1);

	if (ret)
		goto msm_display_init_out;

msm_display_init_out:
	return ret;
}

通過上述方法可以看到，在這裏就可以看到第一幀畫面了。我們來拆分下msm_display_init方法，看他分別作了哪些動作。

mdss_dsi_panel_power()

static int mdss_dsi_panel_power(uint8_t enable,
				struct msm_panel_info *pinfo)
{
	int ret = NO_ERROR;

	if (enable) {
		ret = target_ldo_ctrl(enable, pinfo);
		if (ret) {
			dprintf(CRITICAL, "LDO control enable failed\n");
			return ret;
		}
                ... ...

		/* Panel Reset */
		if (!panelstruct.paneldata->panel_lp11_init) {
			ret = mdss_dsi_panel_reset(enable);
			if (ret) {
				dprintf(CRITICAL, "panel reset failed\n");
				return ret;
			}
		}
		dprintf(SPEW, "Panel power on done\n");
	} else {
		/* Disable panel and ldo */
		ret = mdss_dsi_panel_reset(enable);
		if (ret) {
			dprintf(CRITICAL, "panel reset disable failed\n");
			return ret;
		}

		ret = target_ldo_ctrl(enable, pinfo);
		if (ret) {
			dprintf(CRITICAL, "ldo control disable failed\n");
			return ret;
		}
		dprintf(SPEW, "Panel power off done\n");
	}

	return ret;
}

target_ldo_ctrl()--->regulator_enable()給L2、L6和L17供電。另外是否會進行reset，取決於我們在dtsi中給lp11附的值。

mdss_dsi_panel_clock

調用calculate_clock_config(pinfo)計算時鐘配置和調用target_panel_clock(enable, pinfo)配置目標panel的時鐘。

static uint32_t mdss_dsi_panel_clock(uint8_t enable,
				struct msm_panel_info *pinfo)
{
	uint32_t ret = NO_ERROR;

	ret = calculate_clock_config(pinfo);
	if (ret)
		dprintf(CRITICAL, "Clock calculation failed\n");
	else
		ret = target_panel_clock(enable, pinfo);

	return ret;
}

msm_fb_alloc()&fbcon_setup(&(panel->fb));

爲幀緩衝器(frame buffer)分配內存。

display_image_on_screen()

調用fetch_image_from_partition()從splash分區獲取lk logo圖片，如果splash分區沒有滿足要求的數據，就顯示默認的logo。

void display_image_on_screen(void)
{
#if DISPLAY_TYPE_MIPI
	int fetch_image_from_partition();

	if (fetch_image_from_partition() < 0) {
		display_default_image_on_screen();
	} else {
		/* data has been put into the right place */
		fbcon_flush();
	}
#else
	display_default_image_on_screen();
#endif
}

msm_display_config

① mdss_dsi_phy_init()

如果有兩個MIPI DSI接口MIPI_DSI0和MIPI_DSI1就調用兩次mdss_dsi_phy_init()，msm8909只有MIPI_DSI0，MSM8994等有兩個DSI接口。

② mdss_dsi_host_init()

初始化DSI接口的host控制器。

③ mdss_dsi_panel_pre_init()

根據lp11的值判定是否走reset

        case MIPI_VIDEO_PANEL:
		dprintf(INFO, "Config MIPI_VIDEO_PANEL.\n");

		mdp_rev = mdp_get_revision();
		if (mdp_rev == MDP_REV_50 || mdp_rev == MDP_REV_304 ||
						mdp_rev == MDP_REV_305)
			ret = mdss_dsi_config(panel);
		else
			ret = mipi_config(panel);

		if (ret)
			goto msm_display_config_out;

		if (pinfo->early_config)
			ret = pinfo->early_config((void *)pinfo);

		ret = mdp_dsi_video_config(pinfo, &(panel->fb));
		if (ret)
			goto msm_display_config_out;
		break;

msm_display_on()

int msm_display_on()
{
        ... ...
        case MIPI_VIDEO_PANEL:
		dprintf(INFO, "Turn on MIPI_VIDEO_PANEL.\n");
		ret = mdp_dsi_video_on(pinfo);
		if (ret)
			goto msm_display_on_out;

		ret = mdss_dsi_post_on(panel);
		if (ret)
			goto msm_display_on_out;

		ret = mipi_dsi_on(pinfo);
		if (ret)
			goto msm_display_on_out;
		break;    
        ... ...
}

① 調用mdp_dsi_video_on()使能DSI VIDEO

② mdss_dsi_post_on()使用初始化命令來初始化panel，對應qcom,mdss-dsi-on-command部分。

int mdss_dsi_post_on(struct msm_fb_panel_data *panel)
{
	int ret = 0;
	struct msm_panel_info *pinfo = &(panel->panel_info);

	if (pinfo->mipi.cmds_post_tg) {
		ret = mdss_dsi_panel_initialize(&pinfo->mipi, pinfo->mipi.broadcast);
		if (ret) {
			dprintf(CRITICAL, "dsi panel init error\n");
		}
	}
	return ret;
}

③ mipi_dsi_on()

int mipi_dsi_on(struct msm_panel_info *pinfo)
{
	int ret = NO_ERROR;
	unsigned long ReadValue;
	unsigned long count = 0;

	ReadValue = readl(pinfo->mipi.ctl_base + INT_CTRL) & 0x00010000;

	mdelay(10);

	while (ReadValue != 0x00010000) {
		ReadValue = readl(pinfo->mipi.ctl_base + INT_CTRL) & 0x00010000;
		count++;
		if (count > 0xffff) {
			dprintf(CRITICAL, "Video lane test failed\n");
			return ERROR;
		}
	}

	dprintf(INFO, "Video lane tested successfully\n");
	return ret;
}

mdss_dsi_bl_enable

對應調用mdss_dsi_bl_enable()--->panel_backlight_ctrl(enable)--->target_backlight_ctrl(panelstruct.backlightinfo,enable)

可知根據panelstruct.backlightinfo來進行背光控制，而panelstruct.backlightinfo在oem_panel_select()--->init_panel_data()被賦值

panelstruct->backlightinfo =&xxx_video_backlight;

static int mdss_dsi_bl_enable(uint8_t enable)
{
	int ret = NO_ERROR;

	ret = panel_backlight_ctrl(enable);
	if (ret)
		dprintf(CRITICAL, "Backlight %s failed\n", enable ? "enable" :
							"disable");
	return ret;
}

至此，屏幕已經顯示第一幀畫面，且背光也是正常亮起。lk的顯示已經完成。

其實LK還有一步很重要的工作，就是把我們識別到的屏幕信息傳遞給kernel，它是如何傳遞的呢？下一篇小文檔將會單獨講解該信息的傳遞。

android LCM啓動流程——LK

一、整體流程概述

二、詳細流程分析

1、LK中LCD的唯一入口

target_display_init()

gcdb_display_init()

2、屏幕識別&獲取初始化參數信息

oem_panel_select()

dsi_panel_init

初始化panel結構體

3、屏幕進一步初始化及點亮

mdss_dsi_panel_power()

mdss_dsi_panel_clock

msm_fb_alloc()&fbcon_setup(&(panel->fb));

display_image_on_screen()

msm_display_config

msm_display_on()

mdss_dsi_bl_enable

1、sensor see框架

2、slpi 初始化

I3C簡介

I3C——代碼相關（雜記）

字符轉數字（包含負數）

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

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