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?
-mario
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