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24-bit LCD fbset problem

I am working on TI EZSDK 6.o with Arago distribution. I use a 24-bit 7-inch 800x480 LCD and I can see the Arago desktop nicely. When I fbset my framebuffer, I got a strange values.

 root@am335x-evm:~# fbset

mode "800x480-60"
# D: 33.333 MHz, H: 31.566 kHz, V: 60.125 Hz
geometry 800 480 800 960 32
timings 30000 86 42 33 10 128 2
rgba 8/16,8/8,8/0,8/24
endmode

Shouldn't the geometry be 800 480 800 480 32?

I look at the TI's driver guide at http://processors.wiki.ti.com/index.php/AM335x_LCD_Controller_Driver%27s_Guide

It shows similar results. Could you explain why?

  • Hi Eric,

    The first two parameters are the visible horizontal and vertical resolutions. The next two are the virtual horizontal and virtual vertical resolutions. I'm not very familiar with the frame buffer, but I guess this means that the virtual memory the buffer takes is double in size. Perhaps this is needed for some double buffering mode.

    Best regards,
    Miroslav

  • Hi,

    fbset geometry gives the following info: 

    geometry <xres> <yres> <vxres> <vyres> <depth>
    In our driver da8xx-fb.c vyres is defined as 
    par->vram_size = par->vram_size * LCD_NUM_BUFFERS;
    where LCD_NUM_BUFFERS is defined to b e 2 (two frame buffers per one display)
    That's why the vyres is displayed as double of physical resolution yres.
    BR,
    Vidin