[meta-freescale] Any hope of vblank-synchronized rendering (from vivante) on i.MX6 soon?

[Daiane Angolini]

On Tue, Sep 23, 2014 at 5:09 PM, Carlos Rafael Giani
<dv at pseudoterminal.org> wrote:
> While this is correct for output that is drawn directly to the framebuffer
> (with damage regions etc.), it isn't for compositor-based output, such as
> what Weston does. There, it is not uncommon to repaint  the entire screen.
> If it uses GLES as the backend, this is the only way to do it, unless some
> extension for swapping buffer subregions exists. Perhaps by using a
> compositor in X buffer flipping would be viable.

Carlos, would you mind to open a bug on bugzilla for this VSYNC issue?

It looks like you can describe it better than me. Please add the html
file you shared and the DISTRO_FEATURES needed to reproduce the issue.

Also, please, say which kernel version you used and which GPU version.

I can then, update this with the comments from Prabhu, and change its
status accordingly.

Thanks in advance,
Daiane

>
>
> On 2014-09-23 20:46, Eric Nelson wrote:
>>
>> 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
>
>
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