Linux: Smooth splashscreen with system having weston with drm-backend

[Daniel Vetter]

On Thu, Jul 13, 2017 at 3:33 PM, Vikas Patil <vikasmpatil at gmail.com> wrote:
> Dear All,
>
> I am looking for an solution to have early smooth splashscreen on the
> Linux system with Weston and drm-backend.
>
> I tried showing splashscreen using Linux logo and fbcon Linux features
> but it is not smooth as when system boots logo gets displayed via
> kernel and as the Weston starts
> I see flicker and blackscreen.
>
> Another approach I tried is having standalone drm api based
> application [1] which uses the one of the available hardware
> plane/overlay for displaying splash image and Weston is
> starting and uses default plane which is different from plane utilized
> by above application. but still I see flicker and black screen when
> Weston starts.
>
> I want splash to be displayed on one of the h/w plane and Weston
> should start in background without any flicker and black screen on
> some other plane.
>
> Anyone here before achieved such a use case with such system? Looking
> for inputs/suggestions/ideas to achieve this. It is ok if something
> needs to be hacked/changd at any level (kernel driver, weston).
>
> This is required on platform such as TI (Jacinto) and Intel (Broxton)
> or devices based on drm graphics stack.
>
> [1] http://git.ti.com/glsdk/example-applications/blobs/39080525baca7bf136f2412d62436366a736af6b/drm-tests/drm_z_alpha.c
>
> Thanking you all for your time and inputs in advance.

If you make sure you have matching modes between the 2 users of drm
this should work. kms drivers (especially if they are already
converted to atomic) will automatically optimize transitions to not
flicker (if possible).

If you still flicker then it's either a kernel driver issue, a hw
limitations (some hw needs a full modeset for e.g. changing the bit
depth) or you program two different things.

Also, you must ensure that the boot-splash does not quit until weston
has fully taken over, otherwise kms will first shut down the screen
(when the splash quits), then re-enable it when weston starts.

Cheers, Daniel

>
> Thanks & Regards,
> Vikash
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch