On Thu, Nov 21, 2019 at 12:28 PM Mika Westerberg <mika.westerberg@xxxxxxxxx> wrote: > > On Wed, Nov 20, 2019 at 11:29:33PM +0100, Rafael J. Wysocki wrote: > > > last week or so I found systems where the GPU was under the "PCI > > > Express Root Port" (name from lspci) and on those systems all of that > > > seems to work. So I am wondering if it's indeed just the 0x1901 one, > > > which also explains Mikas case that Thunderbolt stuff works as devices > > > never get populated under this particular bridge controller, but under > > > those "Root Port"s > > > > It always is a PCIe port, but its location within the SoC may matter. > > Exactly. Intel hardware has PCIe ports on CPU side (these are called > PEG, PCI Express Graphics, ports), and the PCH side. I think the IP is > still the same. > > > Also some custom AML-based power management is involved and that may > > be making specific assumptions on the configuration of the SoC and the > > GPU at the time of its invocation which unfortunately are not known to > > us. > > > > However, it looks like the AML invoked to power down the GPU from > > acpi_pci_set_power_state() gets confused if it is not in PCI D0 at > > that point, so it looks like that AML tries to access device memory on > > the GPU (beyond the PCI config space) or similar which is not > > accessible in PCI power states below D0. > > Or the PCI config space of the GPU when the parent root port is in D3hot > (as it is the case here). Also then the GPU config space is not > accessible. Why would the parent port be in D3hot at that point? Wouldn't that be a suspend ordering violation? > I took a look at the HP Omen ACPI tables which has similar problem and > there is also check for Windows 7 (but not Linux) so I think one > alternative workaround would be to add these devices into > acpi_osi_dmi_table[] where .callback is set to dmi_disable_osi_win8 (or > pass 'acpi_osi="!Windows 2012"' in the kernel command line). I'd like to understand the facts that have been established so far before deciding what to do about them. :-)
