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platform:  mtk8937

以下为开机后调用关系：

根据不同的平台，这个函数所在的文件不同; 我们项目属于msm8952系列；

void target_display_init(const char *panel_name){	struct oem_panel_data oem;	int32_t ret = 0;	uint32_t panel_loop = 0;	set_panel_cmd_string(panel_name);	oem = mdss_dsi_get_oem_data();	if (!strcmp(oem.panel, NO_PANEL_CONFIG)		|| !strcmp(oem.panel, SIM_VIDEO_PANEL)		|| !strcmp(oem.panel, SIM_CMD_PANEL)		|| oem.skip) {		dprintf(INFO, "Selected panel: %s\nSkip panel configuration\n",			oem.panel);		return;	}	do {		target_force_cont_splash_disable(false);		ret = gcdb_display_init(oem.panel, MDP_REV_50, (void *)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());	if (!oem.cont_splash) {		dprintf(INFO, "Forcing continuous splash disable\n");		target_force_cont_splash_disable(true);	}}

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;	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;	ret = msm_display_init(&panel);error_gcdb_display_init:	display_enable = ret ? 0 : 1;	return ret;}

int msm_display_init(struct msm_fb_panel_data *pdata){	int ret = NO_ERROR;	panel = pdata;	if (!panel) {		ret = ERR_INVALID_ARGS;		goto msm_display_init_out;	}	/* Turn on panel */	if (pdata->power_func)		ret = pdata->power_func(1, &(panel->panel_info));	if (ret)		goto msm_display_init_out;	if (pdata->dfps_func)		ret = pdata->dfps_func(&(panel->panel_info));	/* Enable clock */	if (pdata->clk_func)		ret = pdata->clk_func(1, &(panel->panel_info));	if (ret)		goto msm_display_init_out;	/* Read specifications from panel if available.	 * If further clocks should be enabled, they can be enabled	 * using pll_clk_func	 */	if (pdata->update_panel_info)		ret = pdata->update_panel_info();	if (ret)		goto msm_display_init_out;	/* Enabled for auto PLL calculation or to enable	 * additional clocks	 */	if (pdata->pll_clk_func)		ret = pdata->pll_clk_func(1, &(panel->panel_info));	if (ret)		goto msm_display_init_out;	/* pinfo prepare  */	if (pdata->panel_info.prepare) {		/* this is for edp which pinfo derived from edid */		ret = pdata->panel_info.prepare();		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;	}	if (ret)		goto msm_display_init_out;	ret = msm_fb_alloc(&(panel->fb));	if (ret)		goto msm_display_init_out;	fbcon_setup(&(panel->fb));	display_image_on_screen();	if ((panel->dsi2HDMI_config) && (panel->panel_info.has_bridge_chip))		ret = panel->dsi2HDMI_config(&(panel->panel_info));	if (ret)		goto msm_display_init_out;	ret = msm_display_config();	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;}

void display_image_on_screen(void){#if DISPLAY_TYPE_MIPI	int fetch_image_from_partition();	dprintf(INFO, "display_image_on_screen-1\n");	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}

void display_default_image_on_screen(void){	unsigned i = 0;	unsigned total_x;	unsigned total_y;	unsigned bytes_per_bpp;	unsigned image_base;#if DISPLAY_TYPE_MIPI	char *image = NULL;#endif	if (!config) {		dprintf(CRITICAL,"NULL configuration, image cannot be displayed\n");		return;	}	fbcon_clear(); // clear screen with Black color	total_x = config->width;	total_y = config->height;	bytes_per_bpp = ((config->bpp) / 8);	image_base = ((((total_y/2) - (SPLASH_IMAGE_HEIGHT / 2) - 1) *			(config->width)) + (total_x/2 - (SPLASH_IMAGE_WIDTH / 2)));#if DISPLAY_TYPE_MIPI#if ENABLE_WBC	image = (pm_appsbl_charging_in_progress() ? image_batt888 : imageBuffer_rgb888);#else	image = imageBuffer_rgb888;#endif	if (bytes_per_bpp == 3) {		for (i = 0; i < SPLASH_IMAGE_HEIGHT; i++) {			memcpy (config->base + ((image_base + (i * (config->width))) * bytes_per_bpp),			image + (i * SPLASH_IMAGE_WIDTH * bytes_per_bpp),			SPLASH_IMAGE_WIDTH * bytes_per_bpp);		}	}	fbcon_flush();#if DISPLAY_MIPI_PANEL_NOVATEK_BLUE	if(is_cmd_mode_enabled())		mipi_dsi_cmd_mode_trigger();#endif#else	if (bytes_per_bpp == 2) {		for (i = 0; i < SPLASH_IMAGE_HEIGHT; i++) {			memcpy (config->base + ((image_base + (i * (config->width))) * bytes_per_bpp),			imageBuffer + (i * SPLASH_IMAGE_WIDTH * bytes_per_bpp),			SPLASH_IMAGE_WIDTH * bytes_per_bpp);		}	}	fbcon_flush();#endif}

fbcon_clear();  // clear screen with Black color

config->width;  // screen total width

config->height  // screen total high

image_base      // 显示的screen的中心基准。

改变这个image_base 的中心基准值，可以改变图片的显示位置。

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