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Atmel LCDC Driver

The atmel_lcdfb driver, supporting both AT91 and AVR32 chips, was merged during the 2.6.22 release cycle. This was based on the old sidsafb driver, but contains a lot of improvements and will eventually replace it. Platform- and board specific code for AT32AP7000 and ATSTK1000 was merged as well, but not the Ltv350qvDriver , which is necessary for initializing the LCD panel on ATSTK1000.

Using the driver

The atmel_lcdfb driver requires a bit of board-specific code to work. First, to add a PlatformDevice for the LCDC, you need to call at32_add_device_lcdc() like this:

at32_add_device_lcdc(0, &board_lcdc_data, fbmem_start, fbmem_size);
The parameters have the following meaning: 1. First, the device ID. Since the AP7000 only has one LCDC device, this must be 0. 1. Then, the board-specific data. This will be explained below. 1. fbmem_start is the physical address of a preallocated framebuffer. The AVR32 core code will initialize this global variable if the argument fbmem=_size_[@_start_] is passed on the command line. 1. fbmem_size is the size of a preallocated framebuffer. The AVR32 core code will initialize this as well from the fbmem= argument. Set it to 0 if you don't want to use a preallocated framebuffer.

Board-specific data

The board-specific data is a struct of type struct atmel_lcdfb_info which is defined in <video/atmel_lcdfb.h>. The following members must be initialized:

Default colour depth in bits per pixel.
Set this to ATMEL_LCDC_DMAEN | ATMEL_LCDC_DMA2DEN. Some chips don't support panning in the x-direction; the AP7000 does.
Make sure this matches your display. This selects between TFT and STN mode among other things. ATMEL_LCDC_MEMOR_BIG should probably always be set on AVR32.
Set this to the address of a struct fb_monspecs type variable. The struct is defined in <linux/fb.h> and must be initialized based on the specifications of your display.
Guard time when the display is powered up. 2 is usually a good value.


The following settings work with the LTV350QV TFT display on ATSTK1000.

static struct fb_videomode __initdata ltv350qv_modes[] = {
      .name      = "320x240 @ 75",
      .refresh   = 75,
      .xres      = 320,      .yres      = 240,
      .pixclock   = KHZ2PICOS(6891),

      .left_margin   = 17,      .right_margin   = 33,
      .upper_margin   = 10,      .lower_margin   = 10,
      .hsync_len   = 16,      .vsync_len   = 1,

      .sync      = 0,
      .vmode      = FB_VMODE_NONINTERLACED,

static struct fb_monspecs __initdata atstk1000_default_monspecs = {
   .manufacturer      = "SNG",
   .monitor      = "LTV350QV",
   .modedb         = ltv350qv_modes,
   .modedb_len      = ARRAY_SIZE(ltv350qv_modes),
   .hfmin         = 14820,
   .hfmax         = 22230,
   .vfmin         = 60,
   .vfmax         = 90,
   .dclkmax      = 30000000,

struct atmel_lcdfb_info __initdata atstk1000_lcdc_data = {
   .default_bpp      = 24,
   .default_dmacon      = ATMEL_LCDC_DMAEN | ATMEL_LCDC_DMA2DEN,
   .default_lcdcon2   = (ATMEL_LCDC_DISTYPE_TFT
               | ATMEL_LCDC_INVCLK
               | ATMEL_LCDC_MEMOR_BIG),
   .default_monspecs   = &atstk1000_default_monspecs,
   .guard_time      = 2,

Known issues

  • STN displays currently don't work. A patch has been posted to fix this.
  • Panning in the y-direction doesn't work. No patch has been posted, but it is probably easy to fix.
r2 - 2007-06-20 - 15:12:14 - HaavardSkinnemoen
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