x4412开发板&ibox卡片电脑项目实战4－在uboot中添加开机LOGO

在uboot中添加开机LOGO，基本上可以归纳为以下四个步骤：

一：初始化LCD控制器相应的寄存器；

二：初始化LCD控制器对应的时钟源；

三：填充framebuffer；

四：打开背光。

在uboot\board\samsung\x4412\x4412.c中，我们在函数board_late_init中添加显示开机LOGO的函数x4412_framebuffer_init()，该函数内嵌了多个函数，他们完成了以上所有步骤。其源码如下：

void x4412_framebuffer_init(void)
{
	exynos4412_clk_initial();				//初始化时钟
	exynos4412_fb_initial();				//初始化LCD寄存器
}

       这里前两个函数用于设置时钟相关寄存器：

void exynos4412_clk_initial(void)
{
	/* Modify LCD clk */
	writel(EXYNOS4412_CLK_SRC_LCD, (readl(EXYNOS4412_CLK_SRC_LCD) & ~(0xf<<0)) | (0x6<<0));
	writel(EXYNOS4412_CLK_DIV_LCD, (readl(EXYNOS4412_CLK_DIV_LCD) & ~(0xf<<0)) | (0x0<<0));

	exynos4412_setup_clocks(24 * 1000 * 1000);
}

整个时钟的配置，在exynos4412-clk.c中。时钟配置完后，我们再来看LCD寄存器初始化函数exynos4412_fb_initial()。

void exynos4412_fb_initial()
{
	struct exynos4412_fb_data_t * dat;

		dat = &vs070cxn;
		
	if( (dat->bits_per_pixel != 16) && (dat->bits_per_pixel != 24) && (dat->bits_per_pixel != 32) )
		return;

	exynos4412_fb.dat = dat;
	exynos4412_fb.surface.info.bits_per_pixel = dat->bits_per_pixel;
	exynos4412_fb.surface.info.bytes_per_pixel = dat->bytes_per_pixel;
	exynos4412_fb.surface.info.red_mask_size = dat->rgba.r_mask;
	exynos4412_fb.surface.info.red_field_pos = dat->rgba.r_field;
	exynos4412_fb.surface.info.green_mask_size = dat->rgba.g_mask;
	exynos4412_fb.surface.info.green_field_pos = dat->rgba.g_field;
	exynos4412_fb.surface.info.blue_mask_size = dat->rgba.b_mask;
	exynos4412_fb.surface.info.blue_field_pos = dat->rgba.b_field;
	exynos4412_fb.surface.info.alpha_mask_size = dat->rgba.a_mask;
	exynos4412_fb.surface.info.alpha_field_pos = dat->rgba.a_field;
	exynos4412_fb.surface.info.fmt = get_pixel_format(&(exynos4412_fb.surface.info));

	exynos4412_fb.surface.w = dat->width;
	exynos4412_fb.surface.h = dat->height;
	exynos4412_fb.surface.pitch = dat->width * dat->bytes_per_pixel;
	exynos4412_fb.surface.flag = SURFACE_PIXELS_DONTFREE;
	exynos4412_fb.surface.pixels = dat->vram_front;

	exynos4412_fb.surface.clip.x = 0;
	exynos4412_fb.surface.clip.y = 0;
	exynos4412_fb.surface.clip.w = dat->width;
	exynos4412_fb.surface.clip.h = dat->height;

	memset(&exynos4412_fb.surface.maps, 0, sizeof(struct surface_maps));
	surface_set_maps(&exynos4412_fb.surface.maps);

	fb_init(&exynos4412_fb);

	exynos4412_display_logo();
	if(dat->backlight)
		dat->backlight(255);
	
}

以上函数基本上都在填充结构体，这里vs070cxn结构体描述了LCD屏的前后肩等相关参数，不同的屏参数不一样。通常，更换不同的屏，主要也就是修改这个结构体的相关参数。

static struct exynos4412_fb_data_t vs070cxn = {
	.regbase			= EXYNOS4412_LCD_BASE,

	.width				= 1024,
	.height				= 600,
	.bits_per_pixel		= 32,
	.bytes_per_pixel	= 4,
	.freq				= 60,

	.output				= EXYNOS4412_FB_OUTPUT_RGB,
	.rgb_mode			= EXYNOS4412_FB_MODE_BGR_P,
	.bpp_mode			= EXYNOS4412_FB_BPP_MODE_32BPP,
	.swap				= EXYNOS4412_FB_SWAP_WORD,

	.rgba = {
		.r_mask			= 8,
		.r_field		= 0,
		.g_mask			= 8,
		.g_field		= 8,
		.b_mask			= 8,
		.b_field		= 16,
		.a_mask			= 8,
		.a_field		= 24,
	},

	.timing = {
		.h_fp			= 160,
		.h_bp			= 140,
		.h_sw			= 20,
		.v_fp			= 12,
		.v_fpe			= 1,
		.v_bp			= 20,
		.v_bpe			= 1,
		.v_sw			= 3,
	},

	.polarity = {
		.rise_vclk		= 0,
		.inv_hsync		= 1,
		.inv_vsync		= 1,
		.inv_vden		= 0,
	},

	.vram_front			= &vram[0][0],
	.vram_back			= &vram[1][0],

	.init				= lcd_init,
	.backlight			= lcd_backlight,
};

       在fb_init()函数中，初始化了一堆LCD相关寄存器：

static void fb_init(struct fb_t * fb)
{
	struct exynos4412_fb_data_t * dat = (struct exynos4412_fb_data_t *)(fb->dat);

	/*
	 * Initial lcd port
	 */
	writel(EXYNOS4412_GPF0_BASE + EXYNOS4412_GPIO_CON, 0x22222222);
	writel(EXYNOS4412_GPF0_BASE + EXYNOS4412_GPIO_DRV, 0xffffffff);
	writel(EXYNOS4412_GPF0_BASE + EXYNOS4412_GPIO_PUD, 0x0);
	writel(EXYNOS4412_GPF1_BASE + EXYNOS4412_GPIO_CON, 0x22222222);
	writel(EXYNOS4412_GPF1_BASE + EXYNOS4412_GPIO_DRV, 0xffffffff);
	writel(EXYNOS4412_GPF1_BASE + EXYNOS4412_GPIO_PUD, 0x0);
	writel(EXYNOS4412_GPF2_BASE + EXYNOS4412_GPIO_CON, 0x22222222);
	writel(EXYNOS4412_GPF2_BASE + EXYNOS4412_GPIO_DRV, 0xffffffff);
	writel(EXYNOS4412_GPF2_BASE + EXYNOS4412_GPIO_PUD, 0x0);
	writel(EXYNOS4412_GPF3_BASE + EXYNOS4412_GPIO_CON, (readl(EXYNOS4412_GPF3_BASE + EXYNOS4412_GPIO_CON) & ~(0xffff<<0)) | (0x2222<<0));
	writel(EXYNOS4412_GPF3_BASE + EXYNOS4412_GPIO_DRV, (readl(EXYNOS4412_GPF3_BASE + EXYNOS4412_GPIO_DRV) & ~(0xff<<0)) | (0xff<<0));
	writel(EXYNOS4412_GPF3_BASE + EXYNOS4412_GPIO_PUD, (readl(EXYNOS4412_GPF3_BASE + EXYNOS4412_GPIO_PUD) & ~(0xff<<0)) | (0x00<<0));

	/*
	 * Lcd init function
	 */
	if(dat->init)
		dat->init();

	/*
	 * Display path selection
	 */
	writel(EXYNOS4412_LCDBLK_CFG, (readl(EXYNOS4412_LCDBLK_CFG) & ~(0x3<<0)) | (0x2<<0));
	writel(EXYNOS4412_LCDBLK_CFG2, (readl(EXYNOS4412_LCDBLK_CFG2) & ~(0x1<<0)) | (0x1<<0));

	/*
	 * Turn off all windows
	 */
	writel(dat->regbase + WINCON0, (readl(dat->regbase + WINCON0) & ~0x1));
	writel(dat->regbase + WINCON1, (readl(dat->regbase + WINCON1) & ~0x1));
	writel(dat->regbase + WINCON2, (readl(dat->regbase + WINCON2) & ~0x1));
	writel(dat->regbase + WINCON3, (readl(dat->regbase + WINCON3) & ~0x1));
	writel(dat->regbase + WINCON4, (readl(dat->regbase + WINCON4) & ~0x1));

	/*
	 * Turn off all windows color map
	 */
	writel(dat->regbase + WIN0MAP, (readl(dat->regbase + WIN0MAP) & ~(1<<24)));
	writel(dat->regbase + WIN1MAP, (readl(dat->regbase + WIN1MAP) & ~(1<<24)));
	writel(dat->regbase + WIN2MAP, (readl(dat->regbase + WIN2MAP) & ~(1<<24)));
	writel(dat->regbase + WIN3MAP, (readl(dat->regbase + WIN3MAP) & ~(1<<24)));
	writel(dat->regbase + WIN4MAP, (readl(dat->regbase + WIN4MAP) & ~(1<<24)));

	/*
	 * Turn off all windows color key and blending
	 */
	writel(dat->regbase + W1KEYCON0, (readl(dat->regbase + W1KEYCON0) & ~(3<<25)));
	writel(dat->regbase + W2KEYCON0, (readl(dat->regbase + W2KEYCON0) & ~(3<<25)));
	writel(dat->regbase + W3KEYCON0, (readl(dat->regbase + W3KEYCON0) & ~(3<<25)));
	writel(dat->regbase + W4KEYCON0, (readl(dat->regbase + W4KEYCON0) & ~(3<<25)));

	/*
	 * Initial lcd controller
	 */
	exynos4412_fb_set_output(dat);
	exynos4412_fb_set_display_mode(dat);
	exynos4412_fb_display_off(dat);
	exynos4412_fb_set_polarity(dat);
	exynos4412_fb_set_timing(dat);
	exynos4412_fb_set_lcd_size(dat);
	exynos4412_fb_set_clock(dat);

	/*
	 * Set lcd video buffer
	 */
	exynos4412_fb_set_buffer_size(dat, 0);
	exynos4412_fb_set_window_position(dat, 0);
	exynos4412_fb_set_window_size(dat, 0);

	/*
	 * Enable window 0 for main display area
	 */
	exynos4412_fb_window0_enable(dat);

	/*
	 * Display on
	 */
	exynos4412_fb_display_on(dat);

	/*
	 * Wait a moment
	 */
//	mdelay(100);
}

紧接着，调用exynos4412_display_logo函数填充framebuffer。

static void exynos4412_display_logo(void)
{
	struct surface_t * screen = exynos4412_screen_surface();
	struct surface_t * logo;
	struct rect_t rect;
	u32_t c;

	exynos4412_screen_flush();
	c = surface_map_color(screen, get_named_color("greenyellow"));
	surface_fill(screen, &screen->clip, c, BLEND_MODE_REPLACE);
	
	disp_hanzi();
	lcd_print(450, 350, 0x00000000, c, "www.9tripod.com");
}

这里填充framebuffer，引用了x4412开发板配套的裸机源码，里面引用了一套绘图机制，我们利用它可以很方便的在LCD上打印字符，输出图片等。这里我们同样引用了裸机里面的汉字显示实验，调用了disp_hanzi函数，在LCD屏上显示几个楷体汉字，同时调用lcd_print函数在汉字下面打印了一串字符串。

       到这里，其实图形已经显示在LCD上了，我们只需打开背光即可看到界面了。在exynos4412_fb_initial函数中，通过回调函数调用了lcd_backlight函数：

static void lcd_backlight(u8_t brightness)
{
	if(brightness)
	{
		writel(EXYNOS4412_GPD0_BASE + EXYNOS4412_GPIO_DAT, (readl(EXYNOS4412_GPD0_BASE + EXYNOS4412_GPIO_DAT) & ~(0x1<<0)) | (0x0<<0));
		writel(EXYNOS4412_GPX3_BASE + EXYNOS4412_GPIO_DAT, (readl(EXYNOS4412_GPX3_BASE + EXYNOS4412_GPIO_DAT) & ~(0x1<<5)) | (0x1<<5));
	}
	else
	{
		writel(EXYNOS4412_GPD0_BASE + EXYNOS4412_GPIO_DAT, (readl(EXYNOS4412_GPD0_BASE + EXYNOS4412_GPIO_DAT) & ~(0x1<<0)) | (0x1<<0));
		writel(EXYNOS4412_GPX3_BASE + EXYNOS4412_GPIO_DAT, (readl(EXYNOS4412_GPX3_BASE + EXYNOS4412_GPIO_DAT) & ~(0x1<<5)) | (0x0<<5));
	}
}

这里通过GPIO口打开背光驱动IC，从而点亮背光。到此，uboot的开机LOGO真实的呈现在我们面前了。

附：编译好的可在x4412&ibox开发板上运行的uboot映像：

http://xboot.org/thread-27358-1-1.html