[maemo-developers] [maemo-developers] examining n800 kernel

From: Daniel Stone daniel.stone at nokia.com
Date: Tue Jan 16 20:57:44 EET 2007
On Tue, Jan 16, 2007 at 02:57:16PM +0100, ext Frantisek Dufka wrote:
> similar setup like N770 but hopefully improved (finally no memory 
> bicycle but proper bus?). The external videochips seems to be from epson 
> too, not 472 but 475 (or 4 in early prototypes?) called Blizzard and 
> Hailstorm. Difference seems to be bigger memory buffer (1280K) that 
> allows 24 bits in 800x480 instead of 16 on N770. See also
> http://www.erd.epson.com/index.php?option=com_docman&task=cat_view&gid=68&Itemid=40
> So the framebuffer is still external but handled by something different. 

Correct.  The bus between the display controller and the LCD controller
(RFBI) isn't exactly blazing fast, though.  We only use the 475.

> OMAP1 uses something called SOSSI, OMAP2 calls it RFBI (remote frame 
> buffer ...) Interesting is that omap framebuffer driver now contains 
> code for synchronization on vblank and preventing tearing effect. It is 
> both in omapfb/blizzard/rfbi code for n800 and also for 
> omapfb/hwa472/sossi code for n770!

Yes: we use this to do vsync for video from the X server.

> Lets hope some variant of this kernel 
> will go into some future n770 firmware. If not we can try to backport it 
> for mplayer. from the code it looks like the pin from 472 chip 
> signalling horizontal or vertical blank perion is indeed connected to 
> something and checked (?) inside sossi driver. The is still no support 
> for display rotation feature of the epson chip.

For the moment, rotation isn't possible in the UI (lots of hardcoded
800x480s abound), so it's not been a high priority on my list, but it is
certainly on it, and I'll hopefully be adding the support at some stage.

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