Windows CE S3C2440A显示驱动编码分析

在Windows CE下显示驱动是一个比较复杂的驱动，不仅仅设计到硬件的操作，还有上层驱动的GDI接口支持，有时候还需要支持DirectDraw等绘图接口。如果所有的编码工作都重新做一遍的话，难度还是挺大的，庆幸的是微软已经把大部分的接口都提供好了，DDI中包含的20个接口函数（以函数指针的方式表示），需要我们实现的也仅仅只有GPEEnableDriver。闲话不多说，我们先来看看S3C2440A_LCD_REG结构体吧，如下所示；

typedef struct {

    UINT32 LCDCON1;             // 0x00

    UINT32 LCDCON2;             // 0x04

    UINT32 LCDCON3;             // 0x08

    UINT32 LCDCON4;             // 0x0C

    UINT32 LCDCON5;             // 0x10

    UINT32 LCDSADDR1;           // 0x14

    UINT32 LCDSADDR2;           // 0x18

    UINT32 LCDSADDR3;           // 0x1C

    UINT32 REDLUT;              // 0x20

    UINT32 GREENLUT;            // 0x24

    UINT32 BLUELUT;             // 0x28

    UINT32 PAD[8];              // 0x2C - 0x48

    UINT32 DITHMODE;            // 0x4C

    UINT32 TPAL;                // 0x50

    UINT32 LCDINTPND;           // 0x54

    UINT32 LCDSRCPND;           // 0x58

    UINT32 LCDINTMSK;           // 0x5C  

    UINT32 TCONSEL;             // 0x60

} S3C2440A_LCD_REG, *PS3C2440A_LCD_REG;

其中这里面的成员分别对应着LCD控制器中的相关的寄存器，一旦映射成功就可以对这些寄存器进行直接性质的操作了。先来看看Eboot是如何对其进行初始化操作的，如下代码；

static void InitDisplay(void)

{

     volatile S3C2440A_IOPORT_REG *s2440IOP = (S3C2440A_IOPORT_REG *)OALPAtoVA(S3C2440A_BASE_REG_PA_IOPORT, FALSE);

     volatile S3C2440A_LCD_REG    *s2440LCD = (S3C2440A_LCD_REG *)OALPAtoVA(S3C2440A_BASE_REG_PA_LCD, FALSE);

     // Set up the LCD controller registers to display a power-on bitmap image.

     s2440IOP->GPCUP     = 0xFFFFFFFF;

     s2440IOP->GPCCON    = 0xAAAAAAAA;

     s2440IOP->GPDUP     = 0xFFFFFFFF;

     s2440IOP->GPDCON    = 0xAAAAAAAA;

     s2440IOP->GPGCON &= ~(3 << 8);                     // Set LCD_PWREN as output

     s2440IOP->GPGCON |=  (1 << 8);

     s2440IOP->GPGDAT |=  (1 << 4);                     // LCD3V3 ON

     //clkval_calc = (WORD)((float)(S3C2440A_HCLK)/(2.0*5000000)+0.5)-1;

     s2440LCD->LCDCON1   =  (CLKVAL_TFT   <<  8) |/* VCLK = HCLK /((CLKVAL + 1) * 2) -> About7Mhz  */

(LCD_MVAL_USED     <<  7) |     /* 0 : Each Frame              */

(3                 <<  5) |     /* TFT LCD Pannel               */

(12                <<  1) |     /* 16bpp Mode                 */

(0                 <<  0) ;     /* Disable LCD Output          */

     s2440LCD->LCDCON2   =  (LCD_VBPD << 24) |      /* VBPD          :   1                     */

                   (LCD_LINEVAL_TFT   << 14) |      /* Vertical Size : 320 - 1                 */

                   (LCD_VFPD          <<  6) |      /* VFPD          :   2                     */

                   (LCD_VSPW          <<  0) ;      /* VSPW          :   1                     */

     s2440LCD->LCDCON3   =  (LCD_HBPD << 19) |      /* HBPD          :   6                     */

                   (LCD_HOZVAL_TFT    <<  8) |      /* HOZVAL_TFT    : 240 - 1                 */

                   (LCD_HFPD              <<  0) ; /* HFPD          :   2                     */

     s2440LCD->LCDCON4   =  (LCD_MVAL <<  8) |      /* MVAL          :  13                     */

                   (LCD_HSPW              <<  0) ;      /* HSPW     :   4                      */

     s2440LCD->LCDCON5   =  (0            << 12) |      /* BPP24BL  : LSB valid                */

                   (1                     << 11) |      /* FRM565 MODE   : 5:6:5 Format           */

                   (0                     << 10) |      /* INVVCLK   : VCLK Falling Edge         */

                   (1                          <<  9) | /* INVVLINE:Inverted Polarity           */

                   (1                          <<  8) | /* INVVFRAME : Inverted Polarity        */

                   (0                          <<  7) | /* INVVD     : Normal                  */

                   (0                          <<  6) | /* INVVDEN   : Normal                   */

                   (0                          <<  5) | /* INVPWREN   : Normal                  */

                   (0                          <<  4) | /* INVENDLINE  : Normal               */

                   (1                          <<  3) | /* PWREN     : Disable PWREN            */

                   (0                          <<  2) | /* ENLEND: Disable LEND signal         */

                   (0                          <<  1) | /* BSWP     : Swap Disable            */

                   (1                          <<  0) ; /* HWSWP   : Swap Enable              */

     s2440LCD->LCDSADDR1 = ((IMAGE_FRAMEBUFFER_DMA_BASE_eboot >> 22)     << 21) |

                          ((M5D(IMAGE_FRAMEBUFFER_DMA_BASE_eboot >> 1)) <<  0);

     s2440LCD->LCDSADDR2 = M5D((IMAGE_FRAMEBUFFER_DMA_BASE_eboot + (LCD_XSIZE_TFT * LCD_YSIZE_TFT * 2)) >> 1);

     s2440LCD->LCDSADDR3 = (((LCD_XSIZE_TFT - LCD_XSIZE_TFT) / 1) << 11) | (LCD_XSIZE_TFT / 1);       

     //s2440LCD->TCONSEL   |= 0x3;

     s2440LCD->TCONSEL   &= (~7);

     //s2440LCD->TCONSEL   |= (0x1<<4);

     s2440LCD->TPAL      = 0x0;       

     s2440LCD->LCDCON1  |= 1;

     // Display a bitmap image on the LCD...

     //memcpy((void *)IMAGE_FRAMEBUFFER_UA_BASE, ScreenBitmap, LCD_ARRAY_SIZE_TFT_16BIT);

     memset((void *)IMAGE_FRAMEBUFFER_UA_BASE_eboot, 0xef, LCD_ARRAY_SIZE_TFT_16BIT);

}

上面的代码已经注释的很清楚，其中IMAGE_FRAMEBUFFER_UA_BASE_eboot指向的是显示屏幕的内存区域，其中主要可以装载RGB256 4MB的图片数据；OALPAtoVA函数的作用是将物理地址转化为虚拟地址，物理地址和虚拟地址的映射表可以在oemaddrtab_cfg.inc文件中可以看到，对应的数组为g_oalAddressTable二维数组。

然而驱动模式下的内存映射API和Eboot完全不同，正如前几节中介绍，驱动的内存映射方式常采用VirtualAlloc、VirtualCopy等函数，如下代码；

v_s2440CLKPWR = (volatile S3C2440A_CLKPWR_REG *)VirtualAlloc(0, sizeof(S3C2440A_CLKPWR_REG), MEM_RESERVE, PAGE_NOACCESS);

VirtualCopy((PVOID)v_s2440CLKPWR, (PVOID)(S3C2440A_BASE_REG_PA_CLOCK_POWER>>8), sizeof(S3C2440A_CLKPWR_REG), PAGE_READWRITE | PAGE_NOCACHE | PAGE_PHYSICAL ))

vm_pIOPreg = (volatile S3C2440A_IOPORT_REG *)VirtualAlloc(0, sizeof(S3C2440A_IOPORT_REG), MEM_RESERVE, PAGE_NOACCESS);

VirtualCopy((PVOID)vm_pIOPreg, (PVOID)(S3C2440A_BASE_REG_PA_IOPORT >> 8), sizeof(S3C2440A_IOPORT_REG), PAGE_PHYSICAL | PAGE_READWRITE | PAGE_NOCACHE))

CursorOn操作

   显示的操作对于上层应用来说，通过微软的封装GDI接口可以实现各种各样的图形绘制，包括简单的线、点、矩形等操作，然而对于系统来说就比较简单了，其中只需要实现最基本的点操作，线操作即可，当然需要复杂的操作还可以扩展。如下介绍CursorOn的操作，这个函数主要实现对鼠标类型的各个操作绘制，相反的还有CursorOff函数操作，如下代码；

if (!m_CursorForcedOff && !m_CursorDisabled && !m_CursorVisible)

     {

         RECTL cursorRectSave = m_CursorRect;

         int   iRotate;

         RotateRectl(&m_CursorRect);

         for (y = m_CursorRect.top; y < m_CursorRect.bottom; y++){

              if (y < 0){

                   continue;

              }

              if (y >= m_nScreenHeightSave){

                   break;

              }

              ptrLine = &ptrScreen[y * m_pPrimarySurface->Stride()];

              cbsLine = &m_CursorBackingStore[(y - m_CursorRect.top) * (m_CursorSize.x * (m_colorDepth >> 3))];

              for (x = m_CursorRect.left; x < m_CursorRect.right; x++){

                   if (x < 0){

                       continue;

                   }

                   if (x >= m_nScreenWidthSave){

                       break;

                   }

                   // x' = x - m_CursorRect.left; y' = y - m_CursorRect.top;

                   // Width = m_CursorSize.x;   Height = m_CursorSize.y;

                   switch (m_iRotate){

                       case DMDO_0:

                            iRotate = (y - m_CursorRect.top)*m_CursorSize.x + x - m_CursorRect.left;

                            break;

                       case DMDO_90:

iRotate = (x - m_CursorRect.left)*m_CursorSize.x + m_CursorSize.y - 1 - (y - m_CursorRect.top);  

                            break;

                       case DMDO_180:

iRotate = (m_CursorSize.y - 1 - (y - m_CursorRect.top))*m_CursorSize.x + m_CursorSize.x - 1 - (x - m_CursorRect.left);

                            break;

                       case DMDO_270:

iRotate = (m_CursorSize.x -1 - (x - m_CursorRect.left))*m_CursorSize.x + y - m_CursorRect.top;

                            break;

                       default:

iRotate = (y - m_CursorRect.top)*m_CursorSize.x + x - m_CursorRect.left;

                            break;

                   }

cbsLine[(x - m_CursorRect.left) * (m_colorDepth >> 3)] = ptrLine[x * (m_colorDepth >> 3)];

                   ptrLine[x * (m_colorDepth >> 3)] &= m_CursorAndShape[iRotate];

                   ptrLine[x * (m_colorDepth >> 3)] ^= m_CursorXorShape[iRotate];

                   if (m_colorDepth > 8)

                   {

cbsLine[(x - m_CursorRect.left) * (m_colorDepth >> 3) + 1] = ptrLine[x * (m_colorDepth >> 3) + 1];

                       ptrLine[x * (m_colorDepth >> 3) + 1] &= m_CursorAndShape[iRotate];

                       ptrLine[x * (m_colorDepth >> 3) + 1] ^= m_CursorXorShape[iRotate];

                       if (m_colorDepth > 16)

                       {

cbsLine[(x - m_CursorRect.left) * (m_colorDepth >> 3) + 2] = ptrLine[x * (m_colorDepth >> 3) + 2];

                            ptrLine[x * (m_colorDepth >> 3) + 2] &= m_CursorAndShape[iRotate];

                            ptrLine[x * (m_colorDepth >> 3) + 2] ^= m_CursorXorShape[iRotate];

                       }

                   }

              }

         }

         m_CursorRect = cursorRectSave;

         m_CursorVisible = TRUE;

     }

    其他还有如电源操作（需要初始化话屏幕，其原理有点像Windows XP的驱动开发模式），绘制各种图形操作等，显示的编码与硬件操作的这块不是很难，只需要继承DDGPE，实现相应的虚拟函数即可，可以说这也是C++高妙之处。随后几节将介绍DDGPE的实现；