[maemo-developers] Does anyone know the mechanism in Nokia's LCD driver?

[From: Siarhei Siamashka]

On Tue, Jan 13, 2009 at 12:23 PM, Felipe Contreras
<felipe.contreras at gmail.com> wrote:
> On Tue, Jan 13, 2009 at 12:05 PM, Igor Stoppa <igor.stoppa at nokia.com> wrote:
>> Hi,
>> On Tue, 2009-01-13 at 18:06 +0800, ext Huang Gao (Gmail) wrote:
>>> Hi, Igor Stoppa:
>>>       Thank you for your reply!
>>>       So can I understand that this hardware FB is not contained in SDRAM
>>> or SRAM, and LCD will refresh itself from this hardware FB by its controller
>>> automatically, without the help of OMAP DMA channel?
>>
>> I'm in no way a display guy but iirc there are 2 modes for refresh:
>> -auto: whatever is written to the framebuffer goes through straight to
>> the LCD
>> -manual: the image needs to be flushed to the LCD
>>
>> If you are interested, you can check it from the kernel source files.
>
> Would the manual mode help to avoid tearing?

Yes, and it does help to avoid tearing. At least this works fine for
XV extension. But getting tearfree scrolling/panning in GTK
applications for example is a bit more challenging. I can provide a
more detailed explanation if anybody is interested.

XV should make a perfect backend for SDL, because it maps fine on SDL
API (SDL_SetVideoMode/SDL_Flip/...). In general, XV is a good backend
for anything that uses double-buffered or triple-buffered
fullscreen/fullwindow blits. It is possible to get ~27.5 frames per
second in 800x480 resolution for 16bpp rgb color format without
tearing. With a lower resolution it is possible to go up to ~55 frames
per second.