Linux LCD驅動(一)——硬體分析和FrameBuffer

阿新 • • 發佈：2019-01-18

/* 畫素時鐘單位是皮秒，而時鐘的單位是赫茲，所以計算公式為：
     * Hz -> picoseconds is / 10^-12
     */
    unsigned long long div = (unsigned long long)clk * pixclk;

    div >>= 12;            /* div / 2^12 */
    do_div(div, 625 * 625UL * 625); /* div / 5^12, do_div巨集定義在asm/div64.h中*/

    return div;
}

/*根據資料手冊按照TFT屏的要求配置LCD控制暫存器1-5*/

static void my2440fb_config_tft_lcd_regs(const struct fb_info *fbinfo, struct s3c2410fb_hw *regs)
{
    const struct my2440fb_var *fbvar = fbinfo->par;
    const struct fb_var_screeninfo *var = &fbinfo->var;

    /*根據色位模式設定LCD控制暫存器1和5，參考資料手冊*/
    switch (var->bits_per_pixel)

    {
        case 1:/*1BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_TFT1BPP;
            break;
        case 2:/*2BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_TFT2BPP;
            break;
        case 4:/*4BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_TFT4BPP;
            break

;
        case 8:/*8BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_TFT8BPP;
            regs->lcdcon5 |= S3C2410_LCDCON5_BSWP | S3C2410_LCDCON5_FRM565;
            regs->lcdcon5 &= ~S3C2410_LCDCON5_HWSWP;
            break;
        case 16:/*16BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_TFT16BPP;
            regs->lcdcon5 &= ~S3C2410_LCDCON5_BSWP;
            regs->lcdcon5 |= S3C2410_LCDCON5_HWSWP;
            break;
        case 32:/*32BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_TFT24BPP;
            regs->lcdcon5 &= ~(S3C2410_LCDCON5_BSWP | S3C2410_LCDCON5_HWSWP | S3C2410_LCDCON5_BPP24BL);
            break;
        default:/*無效的BPP*/
            dev_err(fbvar->dev, "invalid bpp %d/n", var->bits_per_pixel);
    }

    /*設定LCD配置暫存器2、3、4*/
    regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1) |
            S3C2410_LCDCON2_VBPD(var->upper_margin - 1) |
            S3C2410_LCDCON2_VFPD(var->lower_margin - 1) |
            S3C2410_LCDCON2_VSPW(var->vsync_len - 1);

    regs->lcdcon3 = S3C2410_LCDCON3_HBPD(var->right_margin - 1) |
            S3C2410_LCDCON3_HFPD(var->left_margin - 1) |
            S3C2410_LCDCON3_HOZVAL(var->xres - 1);

    regs->lcdcon4 = S3C2410_LCDCON4_HSPW(var->hsync_len - 1);
}

/*根據資料手冊按照STN屏的要求配置LCD控制暫存器1-5*/
static void my2440fb_config_stn_lcd_regs(const struct fb_info *fbinfo, struct s3c2410fb_hw *regs)
{
    const struct my2440fb_var    *fbvar = fbinfo->par;
    const struct fb_var_screeninfo *var = &fbinfo->var;

    int type = regs->lcdcon1 & ~S3C2410_LCDCON1_TFT;
    int hs = var->xres >> 2;
    unsigned wdly = (var->left_margin >> 4) - 1;
    unsigned wlh = (var->hsync_len >> 4) - 1;

    if (type != S3C2410_LCDCON1_STN4)
    {
        hs >>= 1;
    }

    /*根據色位模式設定LCD控制暫存器1，參考資料手冊*/
    switch (var->bits_per_pixel)
    {
        case 1:/*1BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_STN1BPP;
            break;
        case 2:/*2BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_STN2GREY;
            break;
        case 4:/*4BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_STN4GREY;
            break;
        case 8:/*8BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_STN8BPP;
            hs *= 3;
            break;
        case 12:/*12BPP*/
            regs->lcdcon1 |= S3C2410_LCDCON1_STN12BPP;
            hs *= 3;
            break;
        default:/*無效的BPP*/
            dev_err(fbvar->dev, "invalid bpp %d/n", var->bits_per_pixel);
    }

    /*設定LCD配置暫存器2、3、4, 參考資料手冊*/
    if (wdly > 3) wdly = 3;
    if (wlh > 3) wlh = 3;
    regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1);

    regs->lcdcon3 = S3C2410_LCDCON3_WDLY(wdly) |
            S3C2410_LCDCON3_LINEBLANK(var->right_margin / 8) |
            S3C2410_LCDCON3_HOZVAL(hs - 1);

    regs->lcdcon4 = S3C2410_LCDCON4_WLH(wlh);
}

/*配置幀緩衝起始地址暫存器1-3，參考資料手冊*/
static void my2440fb_set_lcdaddr(struct fb_info *fbinfo)
{
    unsigned long saddr1, saddr2, saddr3;
    struct my2440fb_var *fbvar = fbinfo->par;
    void __iomem *regs = fbvar->lcd_base;

    saddr1 = fbinfo->fix.smem_start >> 1;
    saddr2 = fbinfo->fix.smem_start;
    saddr2 += fbinfo->fix.line_length * fbinfo->var.yres;
    saddr2 >>= 1;
    saddr3 = S3C2410_OFFSIZE(0) | S3C2410_PAGEWIDTH((fbinfo->fix.line_length / 2) & 0x3ff);

    writel(saddr1, regs + S3C2410_LCDSADDR1);
    writel(saddr2, regs + S3C2410_LCDSADDR2);
    writel(saddr3, regs + S3C2410_LCDSADDR3);
}

/*顯示空白，blank mode有5種模式，定義在fb.h中，是一個列舉*/
static int my2440fb_blank(int blank_mode, struct fb_info *fbinfo)
{
    struct my2440fb_var *fbvar = fbinfo->par;
    void __iomem *regs = fbvar->lcd_base;

    /*根據顯示空白的模式來設定LCD是開啟還是停止*/
    if (blank_mode == FB_BLANK_POWERDOWN)
    {
        my2440fb_lcd_enable(fbvar, 0);/*在第②步中定義*/
    }
    else
    {
        my2440fb_lcd_enable(fbvar, 1);/*在第②步中定義*/
    }

    /*根據顯示空白的模式來控制臨時調色盤暫存器*/
    if (blank_mode == FB_BLANK_UNBLANK)
    {
        /*臨時調色盤暫存器無效*/
        writel(0x0, regs + S3C2410_TPAL);
    }
    else
    {
        /*臨時調色盤暫存器有效*/
        writel(S3C2410_TPAL_EN, regs + S3C2410_TPAL);
    }

    return 0;
}

/*設定顏色表*/
static int my2440fb_setcolreg(unsigned regno,unsigned red,unsigned green,unsigned blue,unsigned transp,struct fb_info *fbinfo)
{
    unsigned int val;
    struct my2440fb_var *fbvar = fbinfo->par;
    void __iomem *regs = fbvar->lcd_base;

    switch (fbinfo->fix.visual)
    {
        case FB_VISUAL_TRUECOLOR:
            /*真彩色*/
            if (regno < 16)
            {
                u32 *pal = fbinfo->pseudo_palette;

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

                pal[regno] = val;
            }
            break;
        case FB_VISUAL_PSEUDOCOLOR:
            /*偽彩色*/
            if (regno < 256)
            {
                val = (red >> 0) & 0xf800;
                val |= (green >> 5) & 0x07e0;
                val |= (blue >> 11) & 0x001f;

                writel(val, regs + S3C2410_TFTPAL(regno));

                /*修改調色盤*/
                schedule_palette_update(fbvar, regno, val);
            }
            break;
        default:
            return 1;
    }

    return 0;
}

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

/*修改調色盤*/
static void schedule_palette_update(struct my2440fb_var    *fbvar, unsigned int regno, unsigned int val)
{
    unsigned long flags;
    unsigned long irqen;

    /*LCD中斷掛起暫存器基地址*/
    void __iomem *lcd_irq_base = fbvar->lcd_base + S3C2410_LCDINTBASE;

    /*在修改中斷暫存器值之前先遮蔽中斷，將中斷狀態儲存到flags中*/
    local_irq_save(flags);

    fbvar->palette_buffer[regno] = val;

    /*判斷調色盤是否準備就像*/
    if (!fbvar->palette_ready)
    {
        fbvar->palette_ready = 1;

        /*使能中斷遮蔽暫存器*/
        irqen = readl(lcd_irq_base + S3C24XX_LCDINTMSK);
        irqen &= ~S3C2410_LCDINT_FRSYNC;
        writel(irqen, lcd_irq_base + S3C24XX_LCDINTMSK);
    }

    /*恢復被遮蔽的中斷*/
    local_irq_restore(flags);
}

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