LCD笔记（7）LCD驱动程序框架

1. 硬件相关的操作

LCD驱动程序的核心就是：

分配fb_info
设置fb_info
注册fb_info
硬件相关的设置

硬件相关的设置又可以分为3部分：

引脚设置
时钟设置
LCD控制器设置

本节我们使用时钟子系统再设备树中配置好时钟

2. 分析内核自带的驱动程序

2.1 芯片手册

2.2 设备树

我们再设备树中添加这些代码

            lcdif: lcdif@021c8000 {compatible = "fsl,imx6ul-lcdif", "fsl,imx28-lcdif";reg = <0x021c8000 0x4000>;interrupts = <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>;clocks = <&clks IMX6UL_CLK_LCDIF_PIX>,<&clks IMX6UL_CLK_LCDIF_APB>,<&clks IMX6UL_CLK_DUMMY>;   //这个只是为了兼容性clock-names = "pix", "axi", "disp_axi";status = "disabled";};

定义了3个时钟：

pix：Pixel clock，用于LCD接口，设置为LCD手册上的参数
axi：AXI clock，用于传输数据、读写寄存器，使能即可
disp_axi：一个虚拟的时钟，可以不用设置

2.3 代码（内核自带的LCD驱动）

获得时钟

 host->clk_pix = devm_clk_get(&host->pdev->dev, "pix");if (IS_ERR(host->clk_pix)) {host->clk_pix = NULL;ret = PTR_ERR(host->clk_pix);goto fb_release;}host->clk_axi = devm_clk_get(&host->pdev->dev, "axi");if (IS_ERR(host->clk_axi)) {host->clk_axi = NULL;ret = PTR_ERR(host->clk_axi);dev_err(&pdev->dev, "Failed to get axi clock: %d\n", ret);goto fb_release;}host->clk_disp_axi = devm_clk_get(&host->pdev->dev, "disp_axi");if (IS_ERR(host->clk_disp_axi)) {host->clk_disp_axi = NULL;ret = PTR_ERR(host->clk_disp_axi);dev_err(&pdev->dev, "Failed to get disp_axi clock: %d\n", ret);goto fb_release;}

设置频率：只需要设置pixel clock的频率

 ret = clk_set_rate(host->clk_pix,PICOS2KHZ(fb_info->var.pixclock) * 1000U);

使能时钟

     clk_enable_pix(host);clk_prepare_enable(host->clk_pix);clk_enable_axi(host);clk_prepare_enable(host->clk_axi);clk_enable_disp_axi(host);clk_prepare_enable(host->clk_disp_axi);

以下是自己的代码

#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];static struct gpio_desc *bl_gpio;
static struct clk* clk_pix;
static struct clk* clk_axi;/* 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;/* get gpio from device tree */bl_gpio = gpiod_get(&pdev->dev, "backlight", 0);/* config bl_gpio as output */gpiod_direction_output(bl_gpio, 1);/* set val: gpiod_set_value(bl_gpio, status); *//* get clk from device tree */clk_pix = devm_clk_get(&pdev->dev, "pix");clk_axi = devm_clk_get(&pdev->dev, "axi");/* set clk rate */clk_set_rate(clk_pix, 50000000);/* enable clk */clk_prepare_enable(clk_pix);clk_prepare_enable(clk_axi);/* 1.1 分配fb_info */myfb_info = framebuffer_alloc(0, NULL);/* 1.2 设置fb_info *//* a. var : LCD分辨率、颜色格式 */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的虚拟地址 */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的物理地址 */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 注册fb_info */register_framebuffer(myfb_info);/* 1.4 硬件操作 */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)
{/* 反过来操作 *//* 2.1 反注册fb_info */unregister_framebuffer(myfb_info);/* 2.2 释放fb_info */framebuffer_release(myfb_info);iounmap(mylcd_regs);return 0;
}static const struct of_device_id mylcd_of_match[] = {{ .compatible = "100ask,lcd_drv", },{ },
};
MODULE_DEVICE_TABLE(of, simplefb_of_match);static struct platform_driver mylcd_driver = {.driver = {.name = "mylcd",.of_match_table = mylcd_of_match,},.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. 出口 */
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");

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LCD笔记（7）LCD驱动程序框架_配置时钟

1. 硬件相关的操作

2. 分析内核自带的驱动程序

LCD笔记（7）LCD驱动程序框架_配置时钟相关推荐

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