On Thu, Aug 15, 2013 at 04:54:15PM -0600, Alex Williamson wrote: > On Fri, 2013-08-16 at 08:49 +1000, Dave Airlie wrote: > > On Fri, Aug 16, 2013 at 8:43 AM, Alex Williamson > > <alex.williamson@xxxxxxxxxx> wrote: > > > This is intended to add VGA arbiter support for Intel HD graphics on > > > Core processors. The old GMCH registers no longer exist, so even > > > though it appears that i915 participates in VGA arbitration, it doesn't > > > work. On Intel HD graphics we already attempt to disable VGA regions > > > of the device. This makes registering as a VGA client unnecessary since > > > we don't intend to operate differently depending on how many VGA devices > > > are present. We can disable VGA memory regions by clearing a memory > > > enable bit in the VGA MSR. That only leaves VGA IO, which we update > > > the VGA arbiter to know that we don't participate in VGA memory > > > arbitration. We also add a hook on unload to re-enable memory and > > > reinstate VGA memory arbitration. > > > > I would think there is still a VGA disable bit on the Intel device > > somewhere, we'd just need > > Intel to look in the docs and find it. A bit that can nuke both i/o > > and cmd regs. > > The only bit available is in the GGC and is a keyed/locked register that > not only disables VGA memory and I/O, but also modifies the class code > of the device. Early Core processors didn't lock this, but it's > untouchable in newer ones AFAICT. Thanks, I've not found anything else in the docs. And also we _need_ VGA I/O access to make i915_disable_vga() work. It's not 100% clear whether we really need to poke at the sequencer register in modern hardware, but the docs do still list it as a mandatory step. So even if we were to have a global "disable VGA I/O and mem bit" we'd need to make sure we already disabled VGA eg. after resume when the BIOS had a chance to turn the VGA display back on. I think there were also some BIOSen that turned VGA display back on when closing/opening the laptop lid. Not sure what would even happen with those if totally disabled VGA I/O access. I'm not sure they actually frob with the VGA regs though. Could be they just turn on the VGA display bit in the VGA_CONTROL register. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
