[Public] > -----Original Message----- > From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > Sent: Monday, February 7, 2022 10:45 AM > To: Deucher, Alexander <Alexander.Deucher@xxxxxxx> > Cc: Limonciello, Mario <Mario.Limonciello@xxxxxxx>; Bjorn Helgaas > <bhelgaas@xxxxxxxxxx>; Andreas Noever <andreas.noever@xxxxxxxxx>; > open list:PCI SUBSYSTEM <linux-pci@xxxxxxxxxxxxxxx>; open > list:THUNDERBOLT DRIVER <linux-usb@xxxxxxxxxxxxxxx>; Michael Jamet > <michael.jamet@xxxxxxxxx>; Yehezkel Bernat <YehezkelShB@xxxxxxxxx> > Subject: Re: [PATCH 0/2] Mark USB4 controllers as is_thunderbolt > > Hi, > > On Mon, Feb 07, 2022 at 03:00:19PM +0000, Deucher, Alexander wrote: > > [Public] > > > > > -----Original Message----- > > > From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > > > Sent: Monday, February 7, 2022 1:42 AM > > > To: Limonciello, Mario <Mario.Limonciello@xxxxxxx> > > > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; Andreas Noever > > > <andreas.noever@xxxxxxxxx>; open list:PCI SUBSYSTEM <linux- > > > pci@xxxxxxxxxxxxxxx>; open list:THUNDERBOLT DRIVER <linux- > > > usb@xxxxxxxxxxxxxxx>; Michael Jamet <michael.jamet@xxxxxxxxx>; > > > Yehezkel Bernat <YehezkelShB@xxxxxxxxx>; Deucher, Alexander > > > <Alexander.Deucher@xxxxxxx> > > > Subject: Re: [PATCH 0/2] Mark USB4 controllers as is_thunderbolt > > > > > > Hi Mario, > > > > > > On Fri, Feb 04, 2022 at 12:28:18PM -0600, Mario Limonciello wrote: > > > > Various drivers in the kernel use `pci_is_thunderbolt_attached` to > > > > designate behaving differently from a device that is internally in > > > > the machine. This function relies upon the `is_thunderbolt` > > > > designation which checks for a specific capability only set on Intel > controllers. > > > > > > > > Non-Intel USB4 designs should also match this designation so that > > > > they can be treated the same regardless of the host they're connected > to. > > > > > > Not objecting this if really needed but since USB4 is supposed to be > > > transparent to the native (tunneled) protocol, I would rather try to > > > figure out if there is really need to change driver behaviour > > > whether it is connected over USB4 or plugged natively on the PCIe slot. > > > > > > Can you elaborate a bit what kind of functionality needs this? > > > Perhaps we can figure a better alternative? > > > > In the AMD GPU driver we use it to determine which dGPU is built into > > a platform vs. externally connected since the internal one uses ACPI > > for certain things and the external one does not. There are probably > > other ways to determine this, but it's not in place at the moment. > > Can't you check if the device is behind a hotplug bridge? Then for certain it is > "removable". Unfortunately, most (all?) of the root ports on modern platforms are hotplug capable even if the hardware is soldered to the board. > > The other option is to look for ACPI companion (ACPI_COMPANION()) of the > device. AFAICT dGPUs don't have one (as the BIOS does not know in advance > what will be connected to the hotplug ports) whereas internal does typically > have one. Yeah, this is probably the right way to do this. Alex
