2011/11/16 Matthew Garrett mjg59@srcf.ucam.org:
On Wed, Nov 16, 2011 at 06:03:15PM +0100, Michel Dänzer wrote:
I thought the main reason for the delay wasn't broken hardware but to avoid constantly ping-ponging the vblank IRQ between on and off with apps which regularly neeed the vblank counter value, as that could make the counter unreliable. Maybe I'm misremembering though.
If turning it on and off results in the counter value being wrong then surely that's a hardware problem? I've tested that turning it on and off between every IRQ still gives valid counter values on sandybridge.
This, and the thread that contains it, might be interesting:
http://permalink.gmane.org/gmane.comp.video.dri.devel/53201
In summary: there was some resistance to doing this in January, but I couldn't find any legitimate reason.
--Andy