[U-Boot] Allocating a frame buffer in memory

[Steven Zedeck]

Hi,
I am trying to allocate a frame buffer for my LCD code. I think I understand
how to set up the LCC controller in the Atmel AT91SAM9. So thats not the
issue, at least not yet. I need to understand how UBoot allocates a block of
memory for the buffer.

My TFT/LCD is 320x240 and in 24 bit mode, so 3 bytes per pixel. So I think I
need 320x240x3 total bytes. Correct?

In my lib_arm/board.c file, there is the following:
#ifdef CONFIG_LCD
	/* board init may have inited fb_base */
	if (!gd->fb_base) {
#		ifndef PAGE_SIZE
#		  define PAGE_SIZE 4096
#		endif
		/*
		 * reserve memory for LCD display (always full pages)
		 */
		/* bss_end is defined in the board-specific linker script */
		addr = (_bss_end + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
		size = lcd_setmem (addr);
		gd->fb_base = addr;
	}
#endif /* CONFIG_LCD */

Then in lcd.c, there is lcd_setmem which displays:
Reserving 600k for LCD Framebuffer at: 0x23E91000

Even though I call lcd_setmem with an address of: 0x23F27000

Which is the address that I pass to the Atmel LCD controller DMA Address ?
I have been using this: 0x23F27000

Thanks,
Steve
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