On Wed, Feb 10, 2016 at 5:28 PM, Mario Kleiner <mario.kleiner.de@xxxxxxxxx> wrote: > There's another scenario where this zero-ts case can be hit. If the driver > drm_vblank_init()'s - setting all timestamps to zero - and then code starts > using vblanks (drm_vblank_get()) without drm_vblank_on beforehand, which is > afaics the case with nouveau. Unless that's considered an error as well, > we'd need to init the timestamps to something non-zero but harmless like 1 > usecs at drm_vblank_init() time? Both legacy modeset helpers and atomic ones assume by default that you start out with everything disabled. Pre-atomic drivers make that happen by calling disable_unused_functions() to shut down anything the bios has enabled. I think this can't happen. For drivers that do take over bootloader display config they must call vblank_on explicitly themselves, which i915 does. > What makes sense as output here? DRM_WARN_ONCE? I'd go with WARN_ON and tune it down if it's offensive. But WARN_ON patch for 4.6 of course. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html