On Sat, Dec 07, 2024 at 07:44:09PM +0100, Niklas Schnelle wrote: > Trying to enable bwctrl on a Thunderbolt port causes a boot hang on some > systems though the exact reason is not yet understood. As per the spec > Thunderbolt PCIe Downstream Ports have a fake Max Link Speed of 2.5 GT/s > (USB4 v2 sec 11.2.1): > > "Max Link Speed field in the Link Capabilities Register set to 0001b > (data rate of 2.5 GT/s only). > Note: These settings do not represent actual throughput. > Throughput is implementation specific and based on the USB4 Fabric > performance." > > More generally if 2.5 GT/s is the only supported link speed there is no > point in throtteling as this is already the lowest possible PCIe speed > so don't advertise the capability stopping bwctrl from being probed on > these ports. > > Link: https://lore.kernel.org/linux-pci/Z1R4VNwCOlh9Sg9n@xxxxxxxxx/ > Fixes: 665745f27487 ("PCI/bwctrl: Re-add BW notification portdrv as PCIe BW controller") > Tested-by: Niklas Schnelle <niks@xxxxxxxxxx> > Signed-off-by: Niklas Schnelle <niks@xxxxxxxxxx> Makes sense to me, Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
