On Sun, Aug 05, 2012 at 07:20:31PM -0400, Alex Deucher wrote: > On Sun, Aug 5, 2012 at 5:44 PM, Dave Airlie <airlied@xxxxxxxxx> wrote: > > On Mon, Aug 6, 2012 at 7:40 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: > >> On Sun, Aug 05, 2012 at 10:18:38PM +0100, Matthew Garrett wrote: > >>> On Sun, Aug 05, 2012 at 11:14:12PM +0200, Daniel Vetter wrote: > >>> > >>> > I like this approach more - the only other solution I see is to ask the > >>> > currently active driver (i.e. radeon) at bootime for the right mode. Which > >>> > sounds much more hellish and fragile ... > >>> > >>> The "correct" approach is clearly to just have the drm core change the > >>> i2c mux before requesting edid, but that's made difficult because of the > >>> absence of ordering guarantees in initialisation. I don't like quirking > >>> this, since we're then back to the situation of potentially having to > >>> add every new piece of related hardware to the quirk list. > >> > >> The "correct" approach of switching the mux before we fetch the edid is > >> actualy the one I fear will result in fragile code: Only run on few > >> machines, and as you say with tons of funky interactions with the init > >> sequence ordering. And I guess people will bitch&moan about the flickering > >> this will cause ;-) > >> > >> As long as it's only apple shipping multi-gpu machines with > >> broken/non-existing vbt, I'll happily stomach the quirk list entries. > >> They're bad, but imo the lesser evil. > > > > Well in theory you can switch the ddc lines without switching the other lines, > > so we could do a mutex protected mux switch around edid retrival, > > > > Depends on the system. On non-Macs, some systems have a single mux, > others have a separate mux for i2c and display as specified in the > ATPX ACPI methods. Not sure how the Macs do it. I've started > cleaning up the PX radeon code along with a bunch of other radeon > ralated ACPI fixes: > http://cgit.freedesktop.org/~agd5f/linux/log/?h=acpi_patches The Macs mux the i2c and display separately. However they don't support the vendor ACPI interfaces for the mux. The driver that provides the vga_switcheroo handler is separate from the graphics drivers, and the same whether the discrete graphics are Radeon or nVidia. Really to support this in any generic sort of way vga_switcheroo needs to support muxing the DDC separately from the display, but as Matthew pointed out the ordering of initialization could be a problem. Even if we protect the DDC with a mutex how can we guarantee that the switcheroo handler is registered to switch the DDC before i915 is ready to check for an EDID? _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
