android LCM启动流程——LK

目录

一、整体流程概述

二、详细流程分析

1、LK中LCD的唯一入口

target_display_init()

gcdb_display_init()

2、屏幕识别&获取初始化参数信息

oem_panel_select()

dsi_panel_init

初始化panel结构体

3、屏幕进一步初始化及点亮

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

---

一、整体流程概述

    首先从aboot_init开始，去走LCD的初始化流程，在aboot中判断是哪种存储方式和启动方式，然后进入LCD在LK的唯一初始化入口——target_display_init。然后会调用对应的gcdb_display_init方法。判断是哪个屏，并初始化对应的参数，以及对其进行上电，最终点亮屏幕。与此同时在点亮之后，会在aboot中将对应的屏幕信息写入到pbuf中，以便kernel能够获取到对应的屏幕信息，然后加载参数并点亮。如下是简单的流程图：

二、详细流程分析

1、LK中LCD的唯一入口

首先我们从aboot_init方法开始，看如何一步步启动LCD：

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

aboot中省略了系统系统的前期准备以及相关的启动模式，这部分后续文章在进行分析，当前继续分析LCD启动相关。

这里就可以看到我们的入口方法：target_display_init()。

• target_display_init()

    根据不同的平台，此处调用的target_display_init()也是不同的，我们以MSM8909为例。此处调用的是msm8909目录下的Target_display.c文件。我们开始看下target_display_init()的调用流程：

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

	if (target_splash_disable())//如果splash_disable的宏开启，则LK阶段不再初始化LCD，参数等的初始化均在kernel阶段进行
		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方法中最关键的部分即do...while结构。这里会对LCD继续做初始化，即gcdb_display_init方法。该方法在gcdb_display.c (bootable\bootloader\lk\dev\gcdb\display)，我们先来看下该方法的实现：

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;

        //通过读取对应的ID或者mipi回读判断是哪块屏，并将屏幕信息保存在pinfo结构体中
	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;

        //通过获取到的屏幕信息继续进行初始化
	ret = msm_display_init(&panel);

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

    可以看到该方法主要有四个动作：

    ① 选取对应的屏幕：dsi_panel_init()

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

    ② 将初始化信息保存在pinfo中：dsi_panel_init()

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

    ③ 根据panel type初始化panel结构体

    ④ 根据上述信息进一步初始化LCD：msm_display_init()

        ret = msm_display_init(&panel);

2、屏幕识别&获取初始化参数信息

• oem_panel_select()

    该方法同样根据平台不同会各自选取对应的执行文件，我们同样使用MSM8909对应的Oem_panel.c。此方法会根据硬件ID或者回读MIPI的方法来识别不同的屏。然后将识别到的屏幕信息保存在panelstruct结构体中。

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)//获取屏幕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);//获取配置参数
}

    ① 首先我们来看下如何识别不同的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);//获取gpio状态
	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;
	}
}

    此处给出的是通过两个硬件ID脚的状态组合进行识别的。即ID0和ID1。分别有高、低两种状态。两个ID脚的组合可以实现四种状态（00,01,10,11），也就是说我们足够识别四种屏。当然硬件上首先要能够进行区分。

    ② 区分panel id后，我们就可以根据panel id获取不同的配置参数信息：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数据，主要初始化panel_struct结构体数据，然后返回panel类型PANEL_TYPE_DSI（还有EDP和HDMI格式）。据对应的panel_id值将对应的屏幕参数赋值给panelstruct结构体。此结构体对应/dsi-panel-xxx-video.dtsi文件，此结构体主要成员如下：

struct panel_struct {
	struct panel_config         *paneldata;//基本参数信息
	struct panel_resolution     *panelres;//Panel的分辨率、时序参数、极性等数据
	struct color_info           *color;
	struct videopanel_info      *videopanel;
	struct commandpanel_info    *commandpanel;
	struct command_state        *state;
	struct lane_configuration   *laneconfig;//这里可看出只支持到4lane，支持的lane对应的state为1，否则为0
	struct panel_timing         *paneltiminginfo;
	struct panel_reset_sequence *panelresetseq;//对应设备树文件的qcom,mdss-dsi-reset-sequence =<1 20>, <0 20>, <1 20>;这里可让pin状态及演示多久后再修改pin状态。
	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;//间隔值
	uint16_t bl_pmic_controltype;
	char     *bl_pmic_model;
};

• dsi_panel_init

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

    根据panel_info和panelstruct将对应屏幕的参数初始化到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结构体

    初始化panel全局变量的其他结构体成员

                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、屏幕进一步初始化及点亮

    获取到对应的屏幕信息以及参数后，会调用msm_display_init方法，进一步的为屏幕的点亮做初始化的动作。实际在该方法中就开始对屏幕进行上电、第一帧显示动画、背光灯的进行控制。

int msm_display_init(struct msm_fb_panel_data *pdata)
{
	int ret = NO_ERROR;
        ... ...
	/* Turn on panel 给panel上电*/
	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));
        ... ...
        //调用calculate_clock_config(pinfo)计算时钟配置和调用target_panel_clock(enable, pinfo)配置目标panel的时钟。
	if (pdata->pll_clk_func)
		ret = pdata->pll_clk_func(1, &(panel->panel_info));
        ... ...
        //为帧缓冲器(frame buffer)分配内存。
	ret = msm_fb_alloc(&(panel->fb));
	if (ret)
		goto msm_display_init_out;

	fbcon_setup(&(panel->fb));
	display_image_on_screen();//调用fetch_image_from_partition()从splash分区获取lk logo图片，如果splash分区没有满足要求的数据，就显示默认的logo。
        ... ...

	ret = msm_display_config();//根据pinfo->type，比如我们这里是MIPI_VIDEO_PANEL来配置msm平台display，配置时还需要根据MDP(MobileDisplay processor)的版本来调用对应的config函数
	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;
}

通过上述方法可以看到，在这里就可以看到第一帧画面了。我们来拆分下msm_display_init方法，看他分别作了哪些动作。

• 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()给L2、L6和L17供电。另外是否会进行reset，取决于我们在dtsi中给lp11附的值。

• mdss_dsi_panel_clock

    调用calculate_clock_config(pinfo)计算时钟配置和调用target_panel_clock(enable, pinfo)配置目标panel的时钟。

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));

    为帧缓冲器(frame buffer)分配内存。

• display_image_on_screen()

    调用fetch_image_from_partition()从splash分区获取lk logo图片，如果splash分区没有满足要求的数据，就显示默认的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()

    如果有两个MIPI DSI接口MIPI_DSI0和MIPI_DSI1就调用两次mdss_dsi_phy_init()，msm8909只有MIPI_DSI0，MSM8994等有两个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()

    根据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 调用mdp_dsi_video_on()使能DSI VIDEO

    ② mdss_dsi_post_on()使用初始化命令来初始化panel，对应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

    对应调用mdss_dsi_bl_enable()--->panel_backlight_ctrl(enable)--->target_backlight_ctrl(panelstruct.backlightinfo,enable)

可知根据panelstruct.backlightinfo来进行背光控制，而panelstruct.backlightinfo在oem_panel_select()--->init_panel_data()被赋值

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，屏幕已经显示第一帧画面，且背光也是正常亮起。lk的显示已经完成。

    其实LK还有一步很重要的工作，就是把我们识别到的屏幕信息传递给kernel，它是如何传递的呢？下一篇小文档将会单独讲解该信息的传递。