S5PV210(TQ210)学习笔记——LCD驱动编写

网上S5PV210内核移植的文章不是很多，而描述2440和6410内核移植的文章多数是讲如何移植，而非手动编写，但是，韦东山老师的视频中讲述了如何从头编写LCD驱动，当然是以2440为例的，我看过视频之后在TQ210平台上进行了实验，实验成功，详细的原理部分以我现在的水平还难以表达清楚。下载是我自己写的代码，适用于TQ210的7寸电容屏。

#include <linux/module.h>
#include <linux/fb.h>
#include <linux/dma-mapping.h>
#include <linux/clk.h>


static struct fb_info *lcd_info;
unsigned long pseudo_palette[16];

unsigned long *display_control;

volatile unsigned long* gpf0con;
volatile unsigned long* gpf1con;
volatile unsigned long* gpf2con;
volatile unsigned long* gpf3con;
volatile unsigned long* gpd0con;
volatile unsigned long* gpd0dat;
volatile unsigned long* vidcon0;
volatile unsigned long* vidcon1;
volatile unsigned long* vidtcon0;
volatile unsigned long* vidtcon1;
volatile unsigned long* vidtcon2;
volatile unsigned long* wincon0;
volatile unsigned long* vidosd0a;
volatile unsigned long* vidosd0b;
volatile unsigned long* vidosd0c;
volatile unsigned long* vidw00add0b0;
volatile unsigned long* vidw00add1b0;
volatile unsigned long* shodowcon;

struct clk *lcd_clk;


static inline unsigned int chan_to_field(unsigned int chan, struct fb_bitfield *bf)
{
	chan &= 0xffff;
	chan >>= 16 - bf->length;
	return chan << bf->offset;
}

static int lcdfb_setcolreg(unsigned int regno, unsigned int red,
			     unsigned int green, unsigned int blue,
			     unsigned int transp, struct fb_info *info)
{
	unsigned int val;
	
	if (regno > 16)
		return 1;

	/* 用red,green,blue三原色构造出val */
	val  = chan_to_field(red,	&info->var.red);
	val |= chan_to_field(green, &info->var.green);
	val |= chan_to_field(blue,	&info->var.blue);
	
	//((u32 *)(info->pseudo_palette))[regno] = val;
	pseudo_palette[regno] = val;
	return 0;
}

static struct fb_ops lcd_fbops = {
	.owner		= THIS_MODULE,
	.fb_setcolreg	= lcdfb_setcolreg,
	.fb_fillrect	= cfb_fillrect,
	.fb_copyarea	= cfb_copyarea,
	.fb_imageblit	= cfb_imageblit,
};

static int lcd_init(void){
	int ret;

	/*分配fb_info */
	lcd_info = framebuffer_alloc(0, NULL);
	if(lcd_info == NULL){
		printk(KERN_ERR "alloc framebuffer failed!\n");
		return -ENOMEM;
	}

	/* 配置fb_info各成员*/
	/* fix */
	strcpy(lcd_info->fix.id, "s5pv210_lcd");
	lcd_info->fix.smem_len = 800*480*4;
	lcd_info->fix.type = FB_TYPE_PACKED_PIXELS;
	lcd_info->fix.visual = FB_VISUAL_TRUECOLOR;
	lcd_info->fix.line_length = 800*4;

	/* var */
	lcd_info->var.xres = 800;
	lcd_info->var.yres = 480;
	lcd_info->var.xres_virtual = 800;
	lcd_info->var.yres_virtual = 480;
	lcd_info->var.bits_per_pixel = 32;

	lcd_info->var.red.offset = 16;
	lcd_info->var.red.length = 8;
	lcd_info->var.green.offset = 8;
	lcd_info->var.green.length = 8;
	lcd_info->var.blue.offset = 0;
	lcd_info->var.blue.length = 8;
	lcd_info->var.activate = FB_ACTIVATE_NOW;

	lcd_info->screen_size = 800*480*4;
	lcd_info->pseudo_palette = pseudo_palette;

	lcd_info->fbops = &lcd_fbops;
	/* 配置硬件资源*/
	/* 映射内存*/
	display_control = ioremap(0xe0107008,4);
	gpf0con      = ioremap(0xE0200120, 4);
	gpf1con      = ioremap(0xE0200140, 4);
	gpf2con      = ioremap(0xE0200160, 4);
	gpf3con      = ioremap(0xE0200180, 4);
	
	gpd0con      = ioremap(0xE02000A0, 4);
	gpd0dat      = ioremap(0xE02000A4, 4);
	
	vidcon0      = ioremap(0xF8000000, 4);
	vidcon1      = ioremap(0xF8000004, 4);
	vidtcon0     = ioremap(0xF8000010, 4);
	vidtcon1     = ioremap(0xF8000014, 4);
	vidtcon2     = ioremap(0xF8000018, 4);
	wincon0      = ioremap(0xF8000020, 4);
	vidosd0a     = ioremap(0xF8000040, 4);
	vidosd0b     = ioremap(0xF8000044, 4);
	vidosd0c     = ioremap(0xF8000048, 4);
	vidw00add0b0 = ioremap(0xF80000A0, 4);
	vidw00add1b0 = ioremap(0xF80000D0, 4);
	shodowcon    = ioremap(0xF8000034, 4);
	
	/* 配置GPIO*/
	*gpf0con = 0x22222222;
	*gpf1con = 0x22222222;
	*gpf2con = 0x22222222;
	*gpf3con = 0x22222222;
	*gpd0con &= ~0xf;
	*gpd0con |= 0x1;
	*gpd0dat |= 1<<0;
	*display_control = 2<<0;
	/* 使能时钟*/
	lcd_clk = clk_get(NULL, "lcd");
	if (!lcd_clk || IS_ERR(lcd_clk)) {
		printk(KERN_INFO "failed to get lcd clock source\n");
	}
	clk_enable(lcd_clk);
	
	/* 配置LCD控制器*/
	*vidcon0 = (4<<6)|(1<<4);
	*vidcon1 = (1<<6)|(1<<5)|(1<<4);

	*vidtcon0 = (17<<16)|(26<<8)|(4<<0);
	*vidtcon1 = (40<<16)|(214<<8)|(4<<0);
	*vidtcon2 = (479<<11)|(799<<0);

	*wincon0 &= ~(0xf<<2);
	*wincon0 |= (0xb<<2);

	*vidosd0a = (0<<11)|(0<<0);
	*vidosd0b = (799<<11)|(479<<0);
	*vidosd0c = 480*800;
	//物理地址
	lcd_info->screen_base = dma_alloc_writecombine(NULL, 
		lcd_info->fix.smem_len, (dma_addr_t *)&(lcd_info->fix.smem_start), GFP_KERNEL);
	
	*vidw00add0b0 = lcd_info->fix.smem_start;
	*vidw00add1b0 = lcd_info->fix.smem_start + lcd_info->fix.smem_len;

	*shodowcon = 0x1;

	//开启状态
	*wincon0 |= 1;
	*vidcon0 |= 3;
	/* 注册fb_info */
	ret = register_framebuffer(lcd_info);
	return ret;
}

static void lcd_exit(void){
	unregister_framebuffer(lcd_info);
	dma_free_writecombine(NULL, lcd_info->fix.smem_len, 
		(void*)lcd_info->screen_base, (dma_addr_t)lcd_info->fix.smem_start);

	iounmap(shodowcon);
	iounmap(vidw00add1b0);
	iounmap(vidw00add0b0);
	iounmap(vidosd0c);
	iounmap(vidosd0b);
	iounmap(vidosd0a);
	iounmap(wincon0);
	iounmap(vidtcon2);
	iounmap(vidtcon1);
	iounmap(vidtcon0);
	iounmap(vidcon1);
	iounmap(vidcon0);
	iounmap(gpd0dat);
	iounmap(gpd0con);
	iounmap(gpf3con);
	iounmap(gpf2con);
	iounmap(gpf1con);
	iounmap(gpf0con);
	framebuffer_release(lcd_info);
}

module_init(lcd_init);
module_exit(lcd_exit);
MODULE_LICENSE("GPL");

将上面的代码在自己的内核环境下编译，然后下载到开发板上试运行即可。

在安装驱动程序前执行指令：

ls /dev/fb*

如果有fb0或者其他fb*存在，应该修改内和配置，取消其他fb的配置，如果看不到fb*设备，则可以按照如下步骤进行测试。
测试前还需要修改下内核配置，有两个原因：

(1) 内核默认配置下不支持Frame buffer

(2) 我们的驱动程序中用到了三个函数：

	.fb_fillrect	= cfb_fillrect,
	.fb_copyarea	= cfb_copyarea,
	.fb_imageblit	= cfb_imageblit,

这三个函数是引用的内核中的函数，不是我们自行实现的。

鉴于上面两个原因，我们需要配置内核支持Frame buffer和列举出的三个函数，另外，内核中并没有直接配置支持这三个函数的选项，权宜之计，修改下drivers/video目录下的Kconfig文件，在config FB项中添加

select FB_CFB_FILLRECT
select FB_CFB_COPYAREA
select FB_CFB_IMAGEBLIT

添加时一定保证格式正确，参考下该文件下的其他配置项即可。配置完成后执行make menuconfig作如下配置：

Device Drivers  --->
	Graphics support  --->
		<*> Support for frame buffer devices  --->

配置后保存配置，编译内核并将编译好的内核下载到开发板或者NFS运行，同时将编译好的LCD驱动程序拷贝到开发板运行环境中进行安装，如果驱动文件名为lcd.ko，则执行：

insmod lcd.ko

这时，你可以看到屏幕被重新初始化了。虽然LCD已经初始化了，但是不知道如何进行测试，可以按照韦东山老师视频中讲述的方法进行LCD驱动测试，但是我们移植的3.8.3内核默认不支持字库，还需要作其他配置，我是用画线的方式测试的屏幕，这里我讲一下我用的测试方法：

(1) 在Linux主机上编译下面的C++程序

#include <iostream>

unsigned long buffer[480][800] = {0};

void put_long_hex(unsigned long v){ 
    for(int i = 0; i != 4; ++i){
        std::cout.put(static_cast<char>(0xff&(v>>(8*(3-i)))));
    }   
}

int main(){
    for(int i = 0; i != 480; ++i){
        buffer[i][0]   = 0x00ff0000;
        buffer[i][799] = 0x0000ff00;
    }   

    for(int i = 0; i != 800; ++i){
        buffer[0][i]   = 0xff000000;
        buffer[479][i] = 0x00ffff00;
    }   

    for(int i = 0; i != 480; ++i){
        for(int j = 0; j != 800; ++j){
            put_long_hex(buffer[i][j]); 
        }   
    }   
}

编译指令如下：

g++ -o main main.cpp

然后如下方式执行程序：

./main > /nfsroot/rootfs/test.img

我是直接将文件生成在NFS的根文件系统下了，你也可以用其他方式将生成的文件拷贝到开发板运行环境内，然后执行如下指令：

cat test.img > /dev/fb0

这时，就可以在屏幕上看到一个矩形且矩形的四条边颜色不相同。

如果想将驱动编译进内核，并在启动时可以看到小企鹅，可以将上面的驱动拷贝到内核的drivers/video/目录下，命名为tq210_fb.c，然后在该目录下做如下修改：

(1)修改Kconfig，添加TQ210的LCD驱动配置选项

在config FB_S4C项的后面添加如下内容：

config FB_TQ210
    tristate "TQ210 lcd support"
    depends on FB
    select FB_CFB_FILLRECT
    select FB_CFB_COPYAREA
    select FB_CFB_IMAGEBLIT
    ---help---
    Currently the suport is only for the TQ210

(2)修改Makefile，添加如下内容：

obj-$(CONFIG_FB_TQ210)        += tq210_fb.o

(3)退回到内核根目录下，执行make menuconfig并按如下方式配置内核

Device Drivers  --->
	Graphics support  --->
		<*> Support for frame buffer devices  --->
			<*>   TQ210 lcd support
		[*] Bootup logo  --->
			[*]   Standard black and white Linux logo 
			[*]   Standard 16-color Linux logo
			[*]   Standard 224-color Linux logo

然后执行指令make zImage或者make uImage来编译内核，将编译好的内核烧写到开发板或者是放到NFS下即可正常运行。

如果您在开发或配置过程遇到什么问题可以留言讨论。

本文链接：http://blog.csdn.net/girlkoo/article/details/8743732

本文作者：girlkoo