Help Needing With Low-level Double Buffering

[Alain21]

I can seem to get the Double buffering system to work

Here is my init code:
CODE

gRegGP2X2DEng = (TRegGp2x2DEng*)mmap(0, 0x200, PROT_READ|PROT_WRITE, MAP_SHARED, gDevMem, 0xE0020000);
vmem = (u16*)mmap(NULL, 8*1024*1024, PROT_READ|PROT_WRITE, MAP_SHARED, gDevMem, 0x3101000);
m_pFB = vmem;
m_pBB = vmem + 0x280000;

gRegGP2X->LCD_DisplayAdressLow = u32((m_pFB - vmem) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressHigh = u32((m_pFB - vmem) + 0x3101000) >> 16;
gRegGP2X->LCD_DisplayAdressInterlacedLow = u32((m_pFB - vmem) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressInterlacedHigh = u32((m_pFB - vmem) + 0x3101000) >> 16;



gRegGP2X is a bitfield by the way

and here is my flipping :

CODE

while(gRegGP2X->m_regGPIO_In.LCD_VSync);
printf("Wait VSync1\n");
printf("Going to set 0x%x\n", uint((m_pBB - vmem) + 0x3101000));

gRegGP2X->LCD_DisplayAdressLow = u32((m_pBB - vmem) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressHigh = u32((m_pBB - vmem) + 0x3101000) >> 16;
gRegGP2X->LCD_DisplayAdressInterlacedLow = u32((m_pBB - vmem) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressInterlacedHigh = u32((m_pBB - vmem) + 0x3101000) >> 16;

u16* temp = m_pFB;
m_pFB = m_pBB;
m_pBB = temp;

while(!gRegGP2X->m_regGPIO_In.LCD_VSync);
printf("Wait VSync2\n");



in the client code I keep writing to m_pBB ... but all I see is the screen flicker Black/Frame/Black/Frame/

so i suspect that one of them is not fine.
Thx very much

 

[Alain21]

Update I have change some thing after trying to take a look at what is done inside SDL

CODE

vmem= (u16*)mmap(NULL, 8*1024*1024, PROT_READ|PROT_WRITE, MAP_SHARED, gDevMem, 0x3101000);
m_pFB= vmem;
m_pBB= vmem + 0x280000;



to

CODE

vmem= (u16*)mmap(NULL, 5*1024*1024, PROT_READ|PROT_WRITE, MAP_SHARED, gDevMem, 0x3101000);
m_pFB= vmem;
m_pBB= (u16*)(u32(vmem) + 320*240*2);



Put the second buffer right after the first one. And of course changing the reserved zone in UpperMemoryManager

In the client code what I do is
CODE

if(bb == (u16*)0x424ca000){
for(int i= 0; i < 320; ++i){
for(int j= 0; j < 240; ++j){
bb[j*320+i]= 0xFF00;
}
}
}else{
for(int i= 0; i < 320; ++i){
for(int j= 0; j < 240; ++j){
bb[j*320+i]= 0x00FF;
}
}
}



Got it fill one buffer kinda yellow and the other kinda blue .... what I should see is the entire screen flash in yellow and blue. But what I see Is One Frame Entirely Yellow ... and the top Half Yellow Bottom Half Blue ....

What is wrong with my adresses !?!?!

any help is appreciated

 

[Alain21]

Wooo hooo .... found it ... damn it wasn't obvious at all !! ...

If anyone can find the problem in the flip code that I posted previously, that guy is strong !!

I'll post the answer shortly
Alain

 

[rlyeh]

m_pBB= (u16*)(u32(vmem) + 320*240*4);

 

[Alain21]

m_pBB= (u16*)(u32(vmem) + 320*240*4);

nice try but as far as I know there is nothing wrong with that ... the problem was

CODE

gRegGP2X->LCD_DisplayAdressLow = u32((m_pFB - vmem) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressHigh = u32((m_pFB - vmem) + 0x3101000) >> 16;
gRegGP2X->LCD_DisplayAdressInterlacedLow = u32((m_pFB - vmem) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressInterlacedHigh = u32((m_pFB - vmem) + 0x3101000) >> 16;



especially doing :

CODE

m_pFB - vmem



Doing arithmetic operation on pt will result on the number of ELEMENTS between them not the number of BYTES. I was especting a certain number but instead the result was Half of it, so setting the pt in the register was halved so that is why i could see half the FB and half BB.

So I fix it using

CODE

gRegGP2X->LCD_DisplayAdressLow = u32((u32(m_pBB) - u32(vmem)) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressHigh = u32((u32(m_pBB) - u32(vmem)) + 0x3101000) >> 16;
gRegGP2X->LCD_DisplayAdressInterlacedLow = u32((u32(m_pBB) - u32(vmem)) + 0x3101000) & 0xFFFF;
gRegGP2X->LCD_DisplayAdressInterlacedHigh = u32((u32(m_pBB) - u32(vmem)) + 0x3101000) >> 16;



Doing the cast before the arithmetic