Re: Any hope of vblank-synchronized rendering (from vivante) on i.MX6 soon?

[Eric Nelson <eric.nelson@boundarydevices.com>]

Hi Carlos,

On 09/23/2014 10:52 AM, Carlos Rafael Giani wrote:
>
> I wonder why it is single buffered. is it because of the memory
> consumption for a second buffer? The buffers could be flipped,
> eliminating any need for blits, so the memory bandwidth should not be an
> issue.
>

There is a memory bandwidth implication.

Assuming frame buffers A and B in a double-buffered system,
rendering will occur into B while A is displayed, then the
two will be swapped, such that B is displayed and A is the
new rendering output.

In order for apps to only update parts of their windows, any
"dirty" blocks need to be copied from B to A in the process
of the flip.

> On 2014-09-23 18:48, Prabhu S wrote:
>> i.MX6 X11 EGL is single buffered and there is no support for VSYNC.
>> The tearing with X11 is a known issue. We did investigate to fix this,
>> but the solution becomes too hacky and cannot be used in production
>> systems.
>>
>> We are adding VSYNC support in Wayland. eglSwapInterval will be
>> supported for FBDEV and Wayland backends in the upcoming release(in
>> january). So Ozone-wayland can take advantage of this.
>>

?? This is already supported in Wayland, though it is controlled
by an environment variable.

You can see it in action by watching /sys/class/graphics/fb0/pan.

Regards,


Eric