drm: understanding the kernel warning during drm_vblank_cleanup()

[Ville Syrjälä]

On Thu, Nov 29, 2018 at 07:30:45PM +0500, Ahsan Hussain wrote:
> Hi folks,
> 
> I'm new to DRM and trying to understand the warning in 
> drivers/gpu/drm/drm_vblank.c during drm_vblank_cleanup().
> 
> WARN_ON(READ_ONCE(vblank->enabled) &&
>      drm_core_check_feature(dev, DRIVER_MODESET));
> 
> Is the drm driver responsible for making sure that !(vblank->enabled) in 
> the .unbind operation, or is this something related to userspace? What 
> does the warning signify? Git history did not help here at all.

It signifies you haven't cleaned up things properly. Usually what
you would do is call drm_atomic_helper_shutdown() which will also
end up turnng vblank interrupts off, assuming you use
drm_vblank_on()/off() properly.

-- 
Ville Syrjälä
Intel