On Wed, Oct 02, 2013 at 04:42:55PM +0300, ville.syrjala@xxxxxxxxxxxxxxx wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > We have several problems with out VGA handling: > - We try to use the GMCH control VGA disable bit even though it may > be locked > - If we manage to disable VGA throuh GMCH control, we're no longer > able to correctly disable the VGA plane > - Taking part in the VGA arbitration is too expensive for X [1] > > So let's treat the GMCH control VGA disable bit as read-only and leave > it for the BIOS to set, as it was intended. To disable VGA we will use > the VGA misc register, and to disable VGA IO we will disable IO space > completely via the PCI command register. > > But we still need VGA register access during resume (and possibly during > lid event on insane BIOSen) to disable the VGA plane. Also we need to > re-disable VGA memory decode via the VGA misc register on resume. > > Luckily up to gen4, VGA registers can be accessed through MMIO. > Unfortunately from gen5 onwards only the legacy VGA IO port range > works. So on gen5+ we still need IO space to be enabled during those > few special moments when we need to access VGA registers. > > We still want to opt out of VGA arbitration on gen5+, so we have keep > IO space disabled most of the time. And when we do need to poke at VGA > registers, we enable IO space briefly while no one is looking. To > guarantee that no one is looking we will use stop_machine(). > > [1] http://lists.x.org/archives/xorg-devel/2013-September/037763.html > > v2: Use SNB_GMCH_TRL on SNB+ > Use port IO instead of MMIO on CTG/ELK > Add WaEnableVGAAccessThroughIOPort comment > Fix the max number of devices on the bus limit > v3: Allocate the temp space dynamically > Print some errors if we fail to execute the vga "op" due to alloc failure Passes the dGPU test, the SNB laptop, but is doa for CTG. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
