ACTIONS S900 uboot阶段显示模块分析！

首先，显示子系统的相关代码在/u-boot/drivers/video/owl目录下，分析从owl_fb.c开始。

void *video_hw_init(void){	owl_pwm_init(gd->fdt_blob);	owl_dss_init(gd->fdt_blob);	if (owl_fb_init(&g_owl_fb) < 0)		return NULL;	owl_fb_display_on(&g_owl_fb);	return &g_owl_fb.gd;}
video_hw_init无法追踪到上一级，应该是直接在汇编中特定的地址位置来调用。owl_pwm_init(gd->fdt_blob)先点背光，这里不深入分析。
owl_dss_init(gd->fdt_blob)进入显示子系统初始化函数：
void owl_dss_init(const void *blob){	/*	 * core init	 */	owl_ctrl_init();	owl_panel_init();	/*	 * de_xxx init	 */#ifdef CONFIG_VIDEO_OWL_DE_S900	owl_de_s900_init(blob);#endif	/*	 * controllers init	 */#ifdef CONFIG_VIDEO_OWL_DSI	owl_dsic_init(blob);#endif	/*	 * panels init	 */#ifdef CONFIG_VIDEO_OWL_DSI	owl_panel_ls055r3sx01_init(blob);#endif}
上面代码去掉了一些兼容性的代码，只针对S900平台mipi dsi的屏来分析。这部分代码结构还是比较清晰的，分四部分：
第一歩：owl_ctrl_init在ctrl.c文件中，初始化控制器，但还不是具体使用到的控制器，例如dsic控制器用于mipi dsi，这里只是相对于一个所有控制器的管理中心。
owl_panel_init在panel.c文件中，这里是屏终端管理中心。整个这一部分相当于屏和对应控制器的管理中心。
第二歩：owl_de_s900_init，显示引擎初始化，在de_s900.c文件中。
int owl_de_s900_init(const void *blob){	……	owl_de_s9009.blob = blob;  //数据和节点赋值给s900显示引擎	owl_de_s9009.node = node;  	owl_de_register(&owl_de_s9009); //注册s900 显示引擎	……}这里涉及到显示引擎的管理中心de.c这个文件，核心是owl_de_register引擎注册函数：
int owl_de_register(struct owl_de_device *de){	debug("%s/n", __func__);	int tmp, i;	if (de == NULL) {   //注册的显示引擎不能为空		error("de is NULL/n");		return -1;	}	if (cur_de != NULL) {  //不能同时注册多个显示引擎		error("another de is already registered/n");		return -1;	}	cur_de = de;	cur_de->base = fdtdec_get_addr(cur_de->blob, cur_de->node, "reg");	if (cur_de->base == FDT_ADDR_T_NONE) {		error("Cannot find reg address/n");		return -1;	} //获取显示引擎的寄存器地址	debug("%s: base is 0x%llx/n", __func__, cur_de->base);	/* init de gamma state, parse 'gamma_adjust_needed' from DTS */	tmp = fdtdec_get_int(cur_de->blob, cur_de->node, "gamma_adjust_needed", 0);	for (i = 0; i < cur_de->num_paths; i++)		cur_de->paths[i].info.gamma_adjust_needed = tmp; 	/* result check, TODO */	if (cur_de->ops && cur_de->ops->power_on)		cur_de->ops->power_on(cur_de);  // 显示引擎上电	/* result check, TODO */	if (cur_de->ops && cur_de->ops->init)		cur_de->ops->init(cur_de);  //显示引擎初始化	return 0;}通过de.c引擎管理中心的调用，实际执行代码在de_s900.c中（这里就是函数指针的魅力，提升代码的层次性）。下面是s900 de的结构体：
static struct owl_de_device owl_de_s9009 = {	.hw_id			= DE_HW_ID_S900,	.num_paths		= 2,   //支持两个通路同时输出，lcd和	.paths			= de_s900_paths,  	.num_videos		= 2,	.videos			= de_s900_videos,	.ops			= &de_s900_device_ops,};
static struct owl_de_path de_s900_paths[] = {	{		.id			= 0,		.name			= "digit",		.supported_displays	= OWL_DISPLAY_TYPE_HDMI,		.ops			= &de_s900_path_ops,	},	{		.id			= 1,		.name			= "lcd",		.supported_displays	= OWL_DISPLAY_TYPE_LCD					| OWL_DISPLAY_TYPE_DSI					| OWL_DISPLAY_TYPE_EDP					| OWL_DISPLAY_TYPE_DUMMY,		.ops			= &de_s900_path_ops,	},};
static struct owl_de_video de_s900_videos[] = {	{		.id			= 0,		.name			= "video0",		.supported_colors	= ATM9009_SUPPORTED_COLORS,		.ops			= &de_s900_video_ops,	},	{		.id			= 1,		.name			= "video1",		.supported_colors	= ATM9009_SUPPORTED_COLORS,		.ops			= &de_s900_video_ops,	},};
static struct owl_de_device_ops de_s900_device_ops = {	.power_on = de_s900_device_power_on,	.init = de_s900_device_init,	.dump_regs = de_s900_device_dump_regs,};
static struct owl_de_path_ops de_s900_path_ops = {	.enable = de_s900_path_enable,	.apply_info = de_s900_path_apply_info,	.set_go = de_s900_path_set_go,	.set_gamma_table = de_s900_path_set_gamma_table,	.get_gamma_table = de_s900_path_get_gamma_table,	.gamma_enable = de_s900_path_gamma_enable,};
static struct owl_de_video_ops de_s900_video_ops = {	.enable = de_s900_video_enable,	.apply_info = de_s900_video_apply_info,};这段结构体代码有点长，但是很关键，所以全贴出来了。由de管理中心可知，首先是s900 de 上电（这里不分析，不然后面收不回来），然后初始化。
static int de_s900_device_init(struct owl_de_device *de){	uint32_t val;	val = readl(SHARESRAM_CTL); /* share mem */	val |= 0x3;  /* tshi, ebox hdmi use 1 bit, pad edp use 0 bit. */	writel(val, SHARESRAM_CTL);	……}特意把初始化贴出来，是因为发现一个问题 val |= 0x3; 这里初始化的时候，寄存器同时打开了hdmi和mipi/edp，像这种地方要特意找很难找到，所以分析问题的时候，还是要思路清晰，系统的分析，这部分理论上方案公司是不需要修改的。
第三歩：owl_dsic_init(blob);   具体控制器的初始化，在dsic.c文件中。
int owl_dsic_init(const void *blob){	……	dsic->dma_channel = owl_dma_request();	if (!dsic->dma_channel) {		error("%s, owl_dma_request failed!/n", __func__);		return -1;	}//DMA通道申请，传送长包的时候需要用到	dsic->base = fdtdec_get_addr(blob, node, "reg");	if (dsic->base == FDT_ADDR_T_NONE) {		error("Cannot find dsic reg address/n");		return -1;	}	debug("%s: base is 0x%llx/n", __func__, dsic->base);	ret = dsic_parse_config(blob, node, dsic);	if (ret < 0)		goto err_parse_config;	dsic->ctrl = &owl_dsi_ctrl;	owl_ctrl_set_drvdata(&owl_dsi_ctrl, dsic);	ret = owl_ctrl_register(&owl_dsi_ctrl);	if (ret < 0)		goto err_ctrl_register;	return 0;        ……}关键部分为注册dsi控制器owl_ctrl_register(&owl_dsi_ctrl);
struct owl_display_ctrl_ops owl_dsi_ctrl_ops = {	.enable = owl_dsic_enable,	.disable = owl_dsic_disable,	.power_on = owl_dsic_power_on,	.power_off = owl_dsic_power_off,	.aux_read = owl_dsic_aux_read,	.aux_write = owl_dsic_aux_write,};static struct owl_display_ctrl owl_dsi_ctrl = {	.name = "dsi_ctrl",	.type = OWL_DISPLAY_TYPE_DSI,	.ops = &owl_dsi_ctrl_ops,};结构体是灵魂，这是肯定要贴的。控制器注册函数又回到ctrl.c控制器管理中心。
这部分没有特别的，可以注册4个控制器。目前分析的代码中由于edp的宏没关，所有注册了2个控制器，dsic和edpc。
第四歩：owl_panel_ls055r3sx01_init(blob); 具体屏驱动的初始化。
屏驱动这部分就是大家最熟悉的了，简单介绍一下：
在init部分注册屏驱动到panel.c 屏终端管理中心，owl_panel_register(&owl_panel_mipi);
struct owl_panel_ops owl_panel_ls055r3sx01_ops = {	.power_on = panel_ls055r3sx01_power_on,	.power_off = panel_ls055r3sx01_power_off,	.enable = panel_ls055r3sx01_enable,	.disable = panel_ls055r3sx01_disable,};static struct owl_panel owl_panel_mipi = {	.desc = {		.name = "mipi_panel",		.type = OWL_DISPLAY_TYPE_DSI,		.ops = &owl_panel_ls055r3sx01_ops,	},};到这里，owl_dss_init显示子系统的初始化函数分析完毕！通过分析这个过程，把相关的东西都有涉及进来了。后面的分析，也是围绕这些东西，主要就是疏通整个工作流程了。
第二部分：owl_fb_init(&g_owl_fb)，framebuffer的初始化。
static int owl_fb_init(struct owl_fb *fb){	debug("%s/n", __func__);	/*	 * PRimary panel	 */	fb->panel = owl_panel_get_primary_panel();	if (fb->panel == NULL) {		error("no primary panel/n");		return -ENODEV;	} // 首先获取主屏，在dts中配置	debug("%s: primary panel type is %d/n", __func__,	      owl_panel_get_type(fb->panel));	fb->path = owl_de_path_get_by_type(owl_panel_get_type(fb->panel));	if (fb->path == NULL) {		error("can not get de path for primary panel/n");		return -EINVAL;	}  //根据panel类型（在屏驱动获取）来定显示引擎的通道	fb->video = owl_de_video_get_by_id(0);	if (fb->video == NULL) {		error("can not get de video for primary panel/n");		return -EINVAL;	}// 默认0为主通道，获取显示引擎的video	__owl_fb_init(fb, true);	/*	 * second panel	 */	fb->second_panel = owl_panel_get_second_panel();	fb->second_path		= owl_de_path_get_by_type(owl_panel_get_type(fb->second_panel));#if defined(CONFIG_VIDEO_OWL_DE_S700) && !defined(CONFIG_VIDEO_OWL_DE_S700_OTT)	fb->second_video = owl_de_video_get_by_id(3);#else	fb->second_video = owl_de_video_get_by_id(1);#endif	if (fb->second_panel != NULL && fb->second_path != NULL &&	    fb->second_video != NULL) {		__owl_fb_init(fb, false);	} else {		debug("no valid second display device/n");		fb->second_panel = NULL;	}	/*	 * fill to graphic_device	 */	owl_panel_get_draw_size(fb->panel, (int *)&fb->gd.winSizeX,				(int *)&fb->gd.winSizeY);	fb->gd.gdfIndex = owl_color_mode_to_gdf_mode(OWLFB_COLOR_MODE);	fb->gd.gdfBytesPP = owl_dss_get_color_bpp(OWLFB_COLOR_MODE) / 8;	fb->gd.frameAdrs = OWLFB_BUF_ADDR;	debug("%s: pGD info---/n", __func__);	debug("%dx%d, gdfIndex %d, gdfBytesPP %d, frameAdrs %x/n",	      fb->gd.winSizeX, fb->gd.winSizeY, fb->gd.gdfIndex,	      fb->gd.gdfBytesPP, fb->gd.frameAdrs);	return 0;}
static void __owl_fb_init(struct owl_fb *fb, bool is_primary){	struct owl_panel *panel;	struct owl_de_path *path;	struct owl_de_video *video;	struct owl_de_path_info p_info;	struct owl_de_video_info v_info;	debug("%s: is_primary %d/n", __func__, is_primary);	if (is_primary) {		panel = fb->panel;		path = fb->path;		video = fb->video;	} else {		panel = fb->second_panel;		path = fb->second_path;		video = fb->second_video;	}	owl_de_video_set_path(video, path); //根据framebuffer的path来设置DE的video path	/*	 * init path info	 */	owl_de_path_get_info(path, &p_info);  //初始化通道信息	p_info.type = owl_panel_get_type(panel); //获取屏幕类型	owl_panel_get_resolution(panel, (int *)&p_info.width,				 (int *)&p_info.height);  //获取屏幕的分辨率	p_info.vmode = owl_panel_get_vmode(panel);	switch (owl_panel_get_bpp(panel)) {	case 16:		p_info.dither_mode = DITHER_24_TO_16;		break;	case 18:		p_info.dither_mode = DITHER_24_TO_18;		break;	default:		p_info.dither_mode = DITHER_DISABLE;		break;	}	owl_panel_get_gamma(panel, &p_info.gamma_r_val, &p_info.gamma_g_val,				&p_info.gamma_b_val);	owl_de_path_set_info(path, &p_info); //设置DE通道信息	/*	 * init video info	 */	owl_de_video_get_info(video, &v_info);  //初始化video信息	v_info.color_mode = OWLFB_COLOR_MODE;	v_info.blending = OWL_BLENDING_NONE;	v_info.alpha = 0xff;	v_info.xoff = 0;	v_info.yoff = 0;	/* input size is equal to primary panel's draw size */	owl_panel_get_draw_size(fb->panel, (int *)&v_info.width,				(int *)&v_info.height);	v_info.pos_x = 0;	v_info.pos_y = 0;	/* output size is equal to panel's resolution */	owl_panel_get_resolution(panel, (int *)&v_info.out_width,				 (int *)&v_info.out_height);	v_info.addr[0] = OWLFB_BUF_ADDR;	v_info.offset[0] = 0;	v_info.pitch[0] = (owl_dss_get_color_bpp(v_info.color_mode) / 8)			* v_info.width;	owl_de_video_set_info(video, &v_info);  //设置video信息}从framebuffer的init过程，我们可以清楚的了解到显示子系统的一个工作流程：
framebuffer——>de——>path——>video——>panel
细节太多繁杂，不过大部分修改的内容可能都在其中，在这篇文章不发散，不好发散，只能针对问题点分析，我们这篇文章的主要目的是搞清楚流程，然后学习它的设计思路。
第三部分：显示部分owl_fb_display_on(&g_owl_fb);
static void owl_fb_display_on(struct owl_fb *fb){	debug("%s/n", __func__);	debug("%s(primay panel)/n", __func__);	owl_panel_enable(fb->panel);	owl_de_video_enable(fb->video, true);	owl_de_path_enable(fb->path, true);	owl_de_path_set_go(fb->path);	if (fb->second_panel != NULL) {		debug("%s(secondary panel)/n", __func__);		owl_panel_enable(fb->second_panel);		owl_de_video_enable(fb->second_video, true);		owl_de_path_enable(fb->second_path, true);		owl_de_path_set_go(fb->second_path);	}}主要也就是使能panel video path，使能的顺序刚好和数据流的顺序相反。这里不知道顺序有没有影响，没验证过。
OVER,总的来说，这种设计符合我的思维逻辑，太高级了我看不懂，哈哈。
MTK的确实复杂些，看得没这么顺利，但是MTK的用得顺手，这可能就是差距吧。