On Fri, Oct 25, 2019 at 03:00:44PM -0400, Stuart Hayes wrote: > In older PCIe specs, PDS (presence detect) would come up when the > "in-band" presence detect pin connected, and would be up before DLLLA > (link active). > > In PCIe 4.0 (as an ECN) and in PCIe 5.0, there is a new bit to show if > in-band presence detection can be disabled for the slot, and another bit > that disables it--and a recommendation that it should be disabled if it > can be. In addition, certain OEMs disable in-band presence detection > without implementing these bits. > > This means it is possible to get a "card present" interrupt after the > link is up and the driver is loaded. This causes an erroneous removal > of the device driver, followed by an immediate re-probing. > > This patch set defines these new bits, uses them to disable in-band > presence detection if it can be, waits for PDS to go up if in-band > presence detection is disabled, and adds a DMI table that will let us > know if we should assume in-band presence is disabled on a system. FWIW, this series is Reviewed-by: Lukas Wunner <lukas@xxxxxxxxx> Looking at the patches again today, I only spotted a minor cosmetic issue: In patch [1/3] I would have preferred readout of the PCI_EXP_SLTCAP2 register (hunk #3) to be inserted a little further up in pcie_init(), perhaps before reading the PCI_EXP_LNKCAP register. It just looks a little out of place at the end of the function. I would have grouped it together with the other quirks and feature checks further up in the function and I probably would have amended the ctrl_info() to print the status of the inband_presence_disabled flag. In patch [3/3] the DMI check would then likewise have to be moved up in the function. Maybe Bjorn can make this change when applying, and if not, it's not a big deal. Thanks, Lukas
