mini2440 lcd支持
内核版本：linux-2.6.32.2 实验平台：mini2440 + 统宝3.5寸屏（TD035STED4）
1. 添加平台设备
linux中已经定义好了s3c2440的平台设备，定义在plat-s3c24xx/devs.c中：
/* LCD Controller */
static struct resource s3c_lcd_resource[] = {
[0] = {
.start = S3C24XX_PA_LCD,
.end = S3C24XX_PA_LCD + S3C24XX_SZ_LCD - 1,
.flags = IORESOURCE_MEM,
},
[1] = {
.start = IRQ_LCD,
.end = IRQ_LCD,
.flags = IORESOURCE_IRQ,
}
};
static u64 s3c_device_lcd_dmamask = 0xffffffffUL;
struct platform_device s3c_device_lcd = {
.name = "s3c2410-lcd",
.id = -1,
.num_resources = ARRAY_SIZE(s3c_lcd_resource),
.resource = s3c_lcd_resource,
.dev = {
.dma_mask = &s3c_device_lcd_dmamask,
.coherent_dma_mask = 0xffffffffUL
}
};
EXPORT_SYMBOL(s3c_device_lcd);现在要将这个平台设备添加到mini2440_devices这个数组中：
static struct platform_device *mini2440_devices[] __initdata = {
/* ... */
&s3c_device_lcd,
/* ... */
};
2. 为lcd添加参数
在mach-mini2440.c中添加如下内容：
static struct s3c2410fb_display mini2440_lcd_cfg __initdata = {
.lcdcon5 = S3C2410_LCDCON5_FRM565 |
S3C2410_LCDCON5_INVVLINE |
S3C2410_LCDCON5_INVVFRAME |
S3C2410_LCDCON5_PWREN |
S3C2410_LCDCON5_HWSWP,
.type = S3C2410_LCDCON1_TFT,
.width = 0,
.height = 0,
.pixclock = 170000,
.xres = 240,
.yres = 320,
.bpp = 16,
.left_margin = 1,
.right_margin = 26,
.hsync_len = 5,
.upper_margin = 2,
.lower_margin = 5,
.vsync_len = 2,
};
static struct s3c2410fb_mach_info mini2440_fb_info __initdata = {
.displays = &mini2440_lcd_cfg,
.num_displays = 1,
.default_display = 0,
.gpccon = 0xaa955699,
.gpccon_mask = 0xffc003cc,
.gpcup = 0x0000ffff,
.gpcup_mask = 0xffffffff,
.gpdcon = 0xaa95aaa1,
.gpdcon_mask = 0xffc0fff0,
.gpdup = 0x0000faff,
.gpdup_mask = 0xffffffff,
.lpcsel = 0xf82,
};最后将lcd参数赋值给平台设备：
static void __init mini2440_machine_init(void)
{
/* ... */
s3c24xx_fb_set_platdata(&mini2440_fb_info);
/* ... */
}
3. 添加背光驱动
在drivers/video/backlight目录下添加一个新的文件mini2440_backlight.c，内容如下：
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/gpio.h>
#include <asm/uaccess.h>
#include <mach/regs-gpio.h>
static unsigned int bl_state;
static inline void set_bl(int state)
{
bl_state = !!state;
s3c2410_gpio_setpin(S3C2410_GPG(4), bl_state);
}
static inline unsigned char get_bl(void)
{
return bl_state;
}
static ssize_t dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
int ret;
unsigned char str[] = {'0', '1'};
if (!count)
return 0;
ret = copy_to_user(buf, str + get_bl(), sizeof(unsigned char)) ? -EFAULT : 0;
if (ret)
return ret;
return sizeof(unsigned char);
}
static ssize_t dev_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
{
int ret;
unsigned char ch;
if (!count)
return 0;
ret = copy_from_user(&ch, buf, sizeof(unsigned char)) ? -EFAULT : 0;
if (ret)
return ret;
ch &= 0x01;
set_bl(ch);
return count;
}
static struct file_operations dev_fops = {
.owner = THIS_MODULE,
.read = dev_read,
.write = dev_write,
};
static struct miscdevice misc = {
.minor = MISC_DYNAMIC_MINOR,
.name = "backlight",
.fops = &dev_fops,
};
static int __init dev_init(void)
{
s3c2410_gpio_cfgpin(S3C2410_GPG(4), S3C2410_GPIO_OUTPUT);
set_bl(1);
return misc_register(&misc);
}
static void __exit dev_exit(void)
{
misc_deregister(&misc);
}
module_init(dev_init);
module_exit(dev_exit);
MODULE_LICENSE("Dual BSD/GPL");LCD的背光驱动很简单，同LED驱动一样，只需要控制GPIO引脚就可以了，mini2440背光驱动的GPIO口使用的是GPG4，拉高即打开LCD背光，拉低关闭LCD背光。
修改当前目录下的Kconfig和Makefile，在文件末尾添加如下内容：
// Kconfig config BACKLIGHT_MINI2440 tristate "Backlight Driver for MINI2440" depends on BACKLIGHT_LCD_SUPPORT && FB_S3C2410 help backlight driver for mini2440 // Makefile obj-$(CONFIG_BACKLIGHT_MINI2440) += mini2440_backlight.o
可以通过echo 0 > /dev/backlight和echo 1 > /dev/backlight来关闭、打开LCD背光。
4. 内核配置
Device Drivers ---> Graphics support ---> <*> Support for frame buffer devices ---> <*> S3C2410 LCD framebuffer support [*] Backlight & LCD device support ---> <*> Backlight Driver for MINI2440 Console display driver support ---> <*> Framebuffer Console support [*] Bootup logo ---> [*] Standard 224-color Linux logo
注意，必须配置上<*> Framebuffer Console support，开机LOGO才能够被显示出来。