On Sat, Mar 31, 2018 at 12:58:04PM +0300, Mika Westerberg wrote: > On Sat, Mar 31, 2018 at 11:30:17AM +0200, Lukas Wunner wrote: > > > The whole point here is that those are *not* hotplug slots just regular > > > downstream ports. > > > > Okay, understood. Is this about the NHI or XHCI? Because at least > > on Alpine Ridge (C step), the bridge above the XHCI *is* a hotplug > > bridge. Only the bridge above the NHI is not. > > Yes, exactly. I tried to clarify this mechanism a bit better in the > other email I just sent. But in the e-mail you just sent, the bridge above the XHCI is not a hotplug bridge and according to the lspci output of a MacBookPro13,3 I have here, it *is* a hotplug bridge on Alpine Ridge (C step). FWIW, the HDA controller integrated into Nvidia GPUs can be made visible or hidden in a similar fashion by setting a bit in the GPU's config space. Some laptop DSDTs use this to hide the HDA controller on boot (and resume from system sleep) if no HDMI cable is plugged in. I think this behavior is geared towards Windows' driver model. On Linux it's mostly an annoyance and we're considering un-hiding the HDA controller unconditionally from a PCI quirk: https://bugs.freedesktop.org/show_bug.cgi?id=75985 Thanks, Lukas
