On Wed, Aug 17, 2022 at 7:59 PM Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: [snipped] > I had a quick trawl through some Windows stuff for this and > it does seem to do a few extra checks: > - platform must be TGL-H (nothing else has the DPin stuff I guess) > - OpRegion header must indicate dGPU presence Is the dGPU presence denoted by the return bitmask of INTEL_DSM_FN_GET_BIOS_DATA_FUNCS_SUPPORTED? IIUC the mask 20 won't be set when dGPU is not present. > > Otherwise it does call this DSM uncoditionally on boot/S4 resume > so seems like that is the only really validated configuration. > Although it does seem to explicitly turn off displays prior to > the DSM so that does perhaps indicate that those ports might have > also been enabled via the iGPU by the BIOS. Not sure if disabling > the ports would work correctly after the DSM or not. If not then > the DSM call would need to happen after state readout/sanitization > so that we can shut things down gracefully. > > Additionally after the DSM call it scans the FIA TC live state > bits to check for DPin usage. Looks like its trying to make sure > the driver stops poking at the relevant power wells once in DPin > mode. i915 doesn't check that stuff atm so we might end up > mangling something while the dGPU is driving the port. Thanks for investigating this. I am not really familiar with other stuffs you mentioned, but I am happy to test any follow-up patch. Kai-Heng > > -- > Ville Syrjälä > Intel
