On Wed, Feb 21, 2018 at 04:25:08PM +0530, George Cherian wrote: > On 02/21/2018 03:24 PM, Lukas Wunner wrote: > > On Wed, Feb 21, 2018 at 02:58:13PM +0530, George Cherian wrote: > > > I will explain the setup used > > > To the Cavium ThunderX RC the following PLX device is connected. > > > PLX Technology, Inc. PEX 8747 48-Lane, 5-Port PCI Express Gen 3 (8.0 GT/s) > > > Switch > > > There is no device connected downstream to the PLX switch. > > > > > > AFAIU the pcie_port driver probes PLX and enters autosuspend after 100ms > > > since pci_bridge_d3_possible() returns true. > > > > > > And later pci_sysfs_init() ends up doing a config access of PLX which fails > > > with a "synchronous external abort" Thanks for the details! This one *should* be fixed by this patch: https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=pci/virtualization&id=bf6c089ee2ac67eb22c0ff0ac9cc7f9ccd619d90 Any chance you could try that out? > > Then you're missing a pci_config_pm_runtime_get() in pci_sysfs_init() or > > further down in the call stack, rather than a quirk which just papers > > over the issue. > > I have found another configuration where this fails. > Following is the configuration > 1) Connected a PCIe Intel i40 card under the root port. > 2) unbind the i40 driver and bind with vfio-pci driver. > 3) Run lspci in a loop. "lspci -s xx:xx.xx -vvv" > > I get the same synchronous external abort. > In this case the vfio-pci driver probe it moves the device (i40) to > D3hot provided disable_idle_d3 is not set. lspci tries to do > the config_access which fails with synchronous external abort when > the root port transitions to D3hot. This one sounds like we're missing something in this path: pci_read_config pci_config_pm_runtime_get if (parent) pm_runtime_get_sync __pm_runtime_resume(dev, RPM_GET_PUT) rpm_resume It *looks* like rpm_resume() should resume parent devices, i.e., the root port, but I don't know that code at all. Maybe Rafael or Lukas could confirm that? pci_config_pm_runtime_get() knows that config space is always accessible unless the device is in D3cold, so if the target device is in D3hot, it will leave it there. I assume that if/when rpm_resume() resumes the parent bridges, it will resume them all the way to D0. I'm *really* glad you're finding these issues, because on most platforms we would just silently read invalid data (all ones) and the caller would have no idea what's going wrong. Bjorn
