On Sat, Apr 12, 2025 at 05:52:56AM +0200, Lukas Wunner wrote: > On Sat, Apr 12, 2025 at 07:19:56AM +0530, Krishna Chaitanya Chundru wrote: > > Introduce a common API to check if the PCIe link is active, replacing > > duplicate code in multiple locations. > > > > Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx> > > Reviewed-by: Lukas Wunner <lukas@xxxxxxxxx> Looking at this with a fresh pair of eyeballs, I realize there's an issue here, so unfortunately I have to retract the Reviewed-by: pcie_link_is_active() differs from the existing pciehp_check_link_active() in that it returns 0 not only if the link is down, but also if the Config Space read returns with an error. In particular, if Config Space of a hotplug bridge is inaccessible, 0 is returned instead of -ENODEV with this patch. That can happen if the hotplug bridge itself has been hot-removed, which is common with Thunderbolt, but also on servers with nested PCIe switches. The existing invocations of pciehp_check_link_active() do the right thing if the hotplug bridge has been hot-removed, but after this patch they no longer do. For example in this hunk ... > > --- a/drivers/pci/hotplug/pciehp_hpc.c > > +++ b/drivers/pci/hotplug/pciehp_hpc.c > > @@ -584,7 +557,7 @@ static void pciehp_ignore_dpc_link_change(struct controller *ctrl, > > * Synthesize it to ensure that it is acted on. > > */ > > down_read_nested(&ctrl->reset_lock, ctrl->depth); > > - if (!pciehp_check_link_active(ctrl)) > > + if (!pcie_link_is_active(ctrl_dev(ctrl))) > > pciehp_request(ctrl, PCI_EXP_SLTSTA_DLLSC); > > up_read(&ctrl->reset_lock); > > } ... pciehp_request() will be called if the hotplug bridge was hot-removed, which isn't the right thing to do. The current behavior is to do nothing. I realize I steered you in the wrong direction because in my review of your v4 I asked why pcie_link_is_active() doesn't return a bool: https://lore.kernel.org/all/Z72TRBvpzizcgm9S@xxxxxxxxx/ So I sincerely apologize for that! You actually did the right thing in v4 by returning a negative int if the Config Space read returned an error. Thanks, Lukas
