通宝3.5英寸液晶屏驱动的移植
作者：Athurg
话说：前面已经把内核linux-2.6.31成功移植到了mini2440上，可是仔细看看才发现，美中不足的是液晶屏的显示好像整体右移了一截。这个问题在移植内核前就遇到过，当时是因为烧错了内核，把NEC的那个内核zImage_N35烧了。因此，自然而然的就想到了肯定是液晶驱动的问题。
由于mini2440板子上的S3C2440是片内带液晶控制器的，因此，驱动部分用的是公共驱动，就是内核中的drivers/video/s3c2410fb.c这个了。而且从显示上来看，除了发生了位移外，没有别的问题，于是就怀疑是不是配置的问题，遂移步到arch/arm/mach-s3c2440/mach-mini2440.c，一看果然有一个结构体定义液晶的配置：
/* LCD timing and setup */
/*
* This macro simplifies the table bellow
*/
#define _LCD_DECLARE(_clock,_xres,margin_left,margin_right,hsync, \
_yres,margin_top,margin_bottom,vsync, refresh) \
.width = _xres, \
.xres = _xres, \
.height = _yres, \
.yres = _yres, \
.left_margin = margin_left, \
.right_margin = margin_right, \
.upper_margin = margin_top, \
.lower_margin = margin_bottom, \
.hsync_len = hsync, \
.vsync_len = vsync, \
.pixclock = ((_clock*100000000000LL) / \
((refresh) * \
(hsync + margin_left + _xres + margin_right) * \
(vsync + margin_top + _yres + margin_bottom))), \
.bpp = 16,\
.type = (S3C2410_LCDCON1_TFT16BPP |\
S3C2410_LCDCON1_TFT)
struct s3c2410fb_display mini2440_lcd_cfg[] = {
[0] = { /* mini2440 + 3.5" TFT + touchscreen */
_LCD_DECLARE(
7, /* The 3.5 is quite fast */
240, 21, 38, 6, /* x timing */
320, 4, 4, 2, /* y timing */
60), /* refresh rate */
.lcdcon5 = (S3C2410_LCDCON5_FRM565 |
S3C2410_LCDCON5_INVVLINE |
S3C2410_LCDCON5_INVVFRAME |
S3C2410_LCDCON5_PWREN |
S3C2410_LCDCON5_HWSWP),
},
[1] = { /* mini2440 + 7" TFT + touchscreen */
_LCD_DECLARE(
10, /* the 7" runs slower */
800, 40, 40, 48, /* x timing */
480, 29, 3, 3, /* y timing */
50), /* refresh rate */
.lcdcon5 = (S3C2410_LCDCON5_FRM565 |
S3C2410_LCDCON5_INVVLINE |
S3C2410_LCDCON5_INVVFRAME |
S3C2410_LCDCON5_PWREN),
},
/* The VGA shield can outout at several resolutions. All share
* the same timings, however, anything smaller than 1024x768
* will only be displayed in the top left corner of a 1024x768
* XGA output unless you add optional dip switches to the shield.
* Therefore timings for other resolutions have been ommited here.
*/
[2] = {
_LCD_DECLARE(
10,
1024, 1, 2, 2, /* y timing */
768, 200, 16, 16, /* x timing */
24), /* refresh rate, maximum stable,
tested with the FPGA shield */
.lcdcon5 = (S3C2410_LCDCON5_FRM565 |
S3C2410_LCDCON5_HWSWP),
},
[3] = { /* mini2440 + TPO(TongBao) 3.5" TFT + touchscreen */
_LCD_DECLARE(
7, /* The 3.5 is quite fast */
240, 1, 26, 5, /* x timing */
320, 2, 5, 2, /* y timing */
60), /* refresh rate */
.lcdcon5 = (S3C2410_LCDCON5_FRM565 |
S3C2410_LCDCON5_INVVLINE |
S3C2410_LCDCON5_INVVFRAME |
S3C2410_LCDCON5_PWREN |
S3C2410_LCDCON5_HWSWP),
},
};
这么好的代码结构，一看就明白了。再打开友善之臂前几个版本的配置（比如2.6.29的）一看，豁然开朗：
/* LCD driver info */
#if defined(CONFIG_FB_S3C2410_N240320)
#define LCD_WIDTH 240
#define LCD_HEIGHT 320
#define LCD_PIXCLOCK 100000
#define LCD_RIGHT_MARGIN 36
#define LCD_LEFT_MARGIN 19
#define LCD_HSYNC_LEN 5
#define LCD_UPPER_MARGIN 1
#define LCD_LOWER_MARGIN 5
#define LCD_VSYNC_LEN 1
#elif defined(CONFIG_FB_S3C2410_TFT640480)
#define LCD_WIDTH 640
#define LCD_HEIGHT 480
#define LCD_PIXCLOCK 80000
#define LCD_RIGHT_MARGIN 67
#define LCD_LEFT_MARGIN 40
#define LCD_HSYNC_LEN 31
#define LCD_UPPER_MARGIN 25
#define LCD_LOWER_MARGIN 5
#define LCD_VSYNC_LEN 1
#elif defined(CONFIG_FB_S3C2410_T240320)
#define LCD_WIDTH 240
#define LCD_HEIGHT 320
#define LCD_PIXCLOCK 170000
#define LCD_RIGHT_MARGIN 25
#define LCD_LEFT_MARGIN 0
#define LCD_HSYNC_LEN 4
#define LCD_UPPER_MARGIN 1
#define LCD_LOWER_MARGIN 4
#define LCD_VSYNC_LEN 1
#elif defined(CONFIG_FB_S3C2410_TFT800480)
#define LCD_WIDTH 800
#define LCD_HEIGHT 480
#define LCD_PIXCLOCK 40000
#define LCD_RIGHT_MARGIN 67
#define LCD_LEFT_MARGIN 40
#define LCD_HSYNC_LEN 31
#define LCD_UPPER_MARGIN 25
#define LCD_LOWER_MARGIN 5
#define LCD_VSYNC_LEN 1
#elif defined(CONFIG_FB_S3C2410_VGA1024768)
#define LCD_WIDTH 1024
#define LCD_HEIGHT 768
#define LCD_PIXCLOCK 80000
#define LCD_RIGHT_MARGIN 15
#define LCD_LEFT_MARGIN 199
#define LCD_HSYNC_LEN 15
#define LCD_UPPER_MARGIN 1
#define LCD_LOWER_MARGIN 1
#define LCD_VSYNC_LEN 1
#define LCD_CON5 (S3C2410_LCDCON5_FRM565 | S3C2410_LCDCON5_HWSWP)
#endif
这不，按葫芦画瓢，在配置液晶配置结构体数组mini2440_lcd_cfg[] 中添加下面这段内容：
[3] = { /* mini2440 + TPO(TongBao) 3.5" TFT + touchscreen */
_LCD_DECLARE(
7, /* The 3.5 is quite fast */
240, 1, 26, 5, /* x timing */
320, 2, 5, 2, /* y timing */
60), /* refresh rate */
.lcdcon5 = (S3C2410_LCDCON5_FRM565 |
S3C2410_LCDCON5_INVVLINE |
S3C2410_LCDCON5_INVVFRAME |
S3C2410_LCDCON5_PWREN |
S3C2410_LCDCON5_HWSWP),
},
同时，修改一下液晶屏幕初始化选项
static char mini2440_features_str[12] __initdata = "0tb";
为
static char mini2440_features_str[12] __initdata = "3t";
从液晶配置这一点来看，我觉得友善没有2.6.31内核自带的配置合理。友善采用的是宏定义的方式（配置结构体），条件编译内核。所以如果要更换液晶屏，必须重新编译下载内核。但内核采用的是参数化启动的方式（配置结构体数组），这样只需要在内核启动的时候传递一个参数即可支持新的液晶屏。比如这个地方，就可以填写为0～3，自由选择代码中定义了配置的这些液晶屏，也可以自己添加或修改这些配置，然后使用即可。
