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Date: Tue, 9 Aug 2022 19:03:14 +0800 From: Brad Campbell <lists2009@...rfbargle.com> To: Mika Westerberg <mika.westerberg@...ux.intel.com> Cc: linux-kernel@...r.kernel.org Subject: Re: Apple Thunderbolt Display chaining G'day Mika, On 9/8/22 18:55, Mika Westerberg wrote: > Hi, > > On Tue, Aug 09, 2022 at 06:40:54PM +0800, Brad Campbell wrote: >> G'day Mika, >> >> >> On 9/8/22 18:23, Mika Westerberg wrote: >>> Hi, >>> >>> On Mon, Aug 08, 2022 at 09:27:24PM +0800, Brad Campbell wrote: >>>> If I don't authorize the PCIe tunnels and just leave the DP enabled it >>>> works fine also. >>> >>> But you say that it fails on boot when the driver discovers the tunnels, >>> right? So there is really nothing to authorize (they should be already >>> "authorized" by the boot firmware). >>> >>> If I understand correctly this is how it reproduces (the simplest): >>> >>> 1. Connect a single Apple TB1 display to the system >>> 2. Boot it up >>> 3. Wait a while and it hangs >>> >>> If this is the case, then the driver certainly is not creating any >>> PCIe tunnels itself unless there is a bug somewhere. >>> >>> An additional question, does it reproduce with either TB1 display >>> connected or just with specific TB1 display? >>> >> >> No, I've not been clear enough, I'm sorry. I've re-read what I've written below and >> I'm still not sure I'm clear enough. >> >> The firmware never sets anything up. >> >> When I cold boot the machine (from power on), the thunderbolt displays and tunnels >> remain dark until linux initializes the thunderbolt driver the first time. >> >> If I compile the thunderbolt driver into the kernel, or let the initramfs load it >> the displays come up, all PCIe tunnels are established and everything works. >> >> When I reboot the machine (reset button or warm boot), the firmware continues to >> do nothing and all the tunnels remain in place. The machine dies when the thunderbolt >> driver is loaded for a second time. >> >> That might be a reset/warm boot with it compiled in or loaded from iniramfs. >> It may also be me loading it from the command line after booting with it as a >> module and blacklisted. >> >> The problem comes about when the thunderbolt module is loaded while the PCIe tunnels >> are already established. >> >> To reproduce in the easiest manner I compile the thunderbolt driver as a module and >> blacklist it. This prevents it from auto-loading. >> >> I cold boot the machine, let it boot completely then modprobe thunderbolt and authorize >> the tunnels. I then warm boot which lets the kernel detect and init the DP displays >> and detect/configure all the PCIe devices. The thunderbolt driver is not loaded. >> >> The machine comes up, all tunnels are established and all devices work. >> >> If I then modprobe the thunderbolt driver, things break. >> >> This is the hack in my boot script : >> >> # Spark up thunderbolt >> if [ -z "`grep notb /proc/cmdline`" -a -z "`lsusb | grep '05ac:9227'`" ] ; then >> modprobe thunderbolt >> sleep 1 >> echo 1 > /sys/bus/thunderbolt/devices/0-3/authorized >> echo 1 > /sys/bus/thunderbolt/devices/0-303/authorized >> reboot >> fi > > Thanks for the clarification! How about on macOS side, does it work (I > would expect yes)? > It did work flawlessly in MacOS, but as the GPU turned up its toes I can't really test it anymore. The Mac EFI did odd things with the Thunderbolt tunnels, and due to the dying GPU I couldn't warm boot it in Linux anyway. Every reboot had to be a power cycle or it'd hang in the EFI. Regards, Brad
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