On Wed, Feb 10, 2016 at 7:36 PM, Mario Kleiner <mario.kleiner.de@xxxxxxxxx> wrote: > On 02/10/2016 06:17 PM, Daniel Vetter wrote: >> >> 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 >> > > Ok, so does this one have your R-b for stable as is? What about a proper > nouveau fix if i find one? Probably also for 4.6 then, given that this patch > fixes it up good enough for stable? If possible I'd prefer we just fix nouveau up for stable, and do a WARN_ON patch when this ever happens for 4.6. It sounded like you've figured out already what nouveau needs? -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
