Hi guys, I use an AMD RX 570 in a Thunderbolt 3 external GPU box. dmesg gives me the following message: pci 0000:3a:00.0: 8.000 Gb/s available PCIe bandwidth, limited by 2.5 GT/s x4 link at 0000:04:04.0 (capable of 31.504 Gb/s with 8 GT/s x4 link) Here is a tree view of the devices as well as the output of lspci -vvv: https://pastebin.com/CSsS2akZ The critical path of the device tree looks like this: 00:1c.4 Intel Corporation Sunrise Point-LP PCI Express Root Port #5 (rev f1) 03:00.0 Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02) 04:04.0 Intel Corporation JHL6540 Thunderbolt 3 Bridge (C step) [Alpine Ridge 4C 2016] (rev 02) 3a:00.0 Intel Corporation DSL6540 Thunderbolt 3 Bridge [Alpine Ridge 4C 2015] 3b:01.0 Intel Corporation DSL6540 Thunderbolt 3 Bridge [Alpine Ridge 4C 2015] 3c:00.0 Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X/590] (rev ef) Here is the weird part: Accoding to lspci, all of these devices report in their LnkCap that they support 8 GT/s, except the 04:04.0 and 3a:00.0 which say they only support 2.5 GT/s. Contradictory to lspci, sysfs on the other hand says that both of them are capable of 8 GT/s as well: "/sys/bus/pci/devices/0000:04:04.0/max_link_speed" and "/sys/bus/pci/devices/0000:3a:00.0/max_link_speed" are 8 GT/s. It seems that there is a discrepancy between what lspci thinks and what the devices are actually capable of. Questions: 1. Why are there four bridge devices? 04:00.0, 04:01.0 and 04:02.0 look superfluous to me and nothing is connected to them. It actually gives me the feeling that the TB3 driver creates 4 devices with 2.5 GT/s each, instead of one device that can do the full 8 GT/s. 2. Why are some of the bridge devices only capable of 2.5 GT/s according to lspci? 3. Is it possible to manually set them to 8 GT/s? Thanks in advance for your answers! Best regards, Tim _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
