LCD notes (5) LCD driver framework_ Use device tree

Linux The driver = Driver framework + Hardware programming . Based on QEMU Write the LCD The driver , Yes LCD The framework of the driver has been analyzed clearly . The core is ：

• Distribute fb_info

• Set up fb_info

• register fb_info

• Hardware related settings

We write drivers based on the device tree .

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/fb.h>
#include <linux/init.h>
#include <linux/dma-mapping.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/io.h>

#include <asm/div64.h>

#include <asm/mach/map.h>

struct lcd_regs {
	volatile unsigned int fb_base_phys;
	volatile unsigned int fb_xres;
	volatile unsigned int fb_yres;
	volatile unsigned int fb_bpp;	
};

static struct lcd_regs *mylcd_regs;

static struct fb_info *myfb_info;

static unsigned int pseudo_palette[16];

/* from pxafb.c */
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 mylcd_setcolreg(unsigned regno,
			       unsigned red, unsigned green, unsigned blue,
			       unsigned transp, struct fb_info *info)
{
	unsigned int val;

	/* dprintk("setcol: regno=%d, rgb=%d,%d,%d\n",
		   regno, red, green, blue); */

	switch (info->fix.visual) {
	case FB_VISUAL_TRUECOLOR:
		/* true-colour, use pseudo-palette */

		if (regno < 16) {
			u32 *pal = info->pseudo_palette;

			val  = chan_to_field(red,   &info->var.red);
			val |= chan_to_field(green, &info->var.green);
			val |= chan_to_field(blue,  &info->var.blue);

			pal[regno] = val;
		}
		break;

	default:
		return 1;	/* unknown type */
	}

	return 0;
}


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

static int mylcd_probe(struct platform_device *pdev)
{
	dma_addr_t phy_addr;
	
	/* 1.1  Distribute fb_info */
	myfb_info = framebuffer_alloc(0, NULL);

	/* 1.2  Set up fb_info */     // The pin settings will be put in the device tree 
	/* a. var : LCD The resolution of the 、 Color format  */
	myfb_info->var.xres_virtual = myfb_info->var.xres = 500;
	myfb_info->var.yres_virtual = myfb_info->var.yres = 300;
	
	myfb_info->var.bits_per_pixel = 16;  /* rgb565 */
	myfb_info->var.red.offset = 11;
	myfb_info->var.red.length = 5;

	myfb_info->var.green.offset = 5;
	myfb_info->var.green.length = 6;

	myfb_info->var.blue.offset = 0;
	myfb_info->var.blue.length = 5;
	

	/* b. fix */
	strcpy(myfb_info->fix.id, "100ask_lcd");
	myfb_info->fix.smem_len = myfb_info->var.xres * myfb_info->var.yres * myfb_info->var.bits_per_pixel / 8;
	if (myfb_info->var.bits_per_pixel == 24)
		myfb_info->fix.smem_len = myfb_info->var.xres * myfb_info->var.yres * 4;


	/* fb The virtual address of  */
	myfb_info->screen_base = dma_alloc_wc(NULL, myfb_info->fix.smem_len, &phy_addr,
					 GFP_KERNEL);
	myfb_info->fix.smem_start = phy_addr;  /* fb The physical address of  */
	
	myfb_info->fix.type = FB_TYPE_PACKED_PIXELS;
	myfb_info->fix.visual = FB_VISUAL_TRUECOLOR;

	myfb_info->fix.line_length = myfb_info->var.xres * myfb_info->var.bits_per_pixel / 8;
	if (myfb_info->var.bits_per_pixel == 24)
		myfb_info->fix.line_length = myfb_info->var.xres * 4;
	

	/* c. fbops */
	myfb_info->fbops = &myfb_ops;
	myfb_info->pseudo_palette = pseudo_palette;


	/* 1.3  register fb_info */
	register_framebuffer(myfb_info);

	/* 1.4  Hardware operation  */
	mylcd_regs = ioremap(0x021C8000, sizeof(struct lcd_regs));
	mylcd_regs->fb_base_phys = phy_addr;
	mylcd_regs->fb_xres = 500;
	mylcd_regs->fb_yres = 300;
	mylcd_regs->fb_bpp  = 16;

	return 0;
}


static int mylcd_remove(struct platform_device *pdev)
{
	/*  Reverse operation  */
	/* 2.1  Anti registration fb_info */
	unregister_framebuffer(myfb_info);

	/* 2.2  Release fb_info */
	framebuffer_release(myfb_info);
	
	iounmap(mylcd_regs);

	return 0;
}


static const struct of_device_id mylcd_of_match[] = {
	{ .compatible = "100ask,lcd_drv", }, // Find... In the device tree 100ask,lcd_drv This attribute , You can use this driver 
	{ },
};
MODULE_DEVICE_TABLE(of, simplefb_of_match);

static struct platform_driver mylcd_driver = {
	.driver = {
		.name = "mylcd",
		.of_match_table = mylcd_of_match,  // Define an array , Which device can use this driver 
	},
	.probe = mylcd_probe,
	.remove = mylcd_remove,
};

static int __init lcd_drv_init(void)
{
	int ret;
	struct device_node *np;

	ret = platform_driver_register(&mylcd_driver);
	if (ret)
		return ret;

	return 0;
}

/* 2.  exit  */
static void __exit lcd_drv_exit(void)
{
	platform_driver_unregister(&mylcd_driver);
}


module_init(lcd_drv_init);
module_exit(lcd_drv_exit);

MODULE_AUTHOR("www.100ask.net");
MODULE_DESCRIPTION("Framebuffer driver for the linux");
MODULE_LICENSE("GPL");

2. Entry function registration platform_driver

3. The device tree has corresponding nodes

                framebuffer-mylcd {
                        compatible = "100ask,lcd_drv";
                };

4. To write probe function

• Distribute fb_info

• Set up fb_info

• register fb_info

• Hardware related settings

  • Pin settings

  • The clock is set

  • LCD Controller settings