On Friday, February 16, 2018 11:50:11 PM CET Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelg...@google.com>
>
> Previously we called pci_probe_reset_function() in this path:
>
> pci_sysfs_init # late_initcall
> for_each_pci_dev(dev)
> pci_create_sysfs_dev_files(dev)
> pci_create_capabilities_sysfs(dev)
> pci_probe_reset_function
> pci_dev_specific_reset
> pcie_has_flr
> pcie_capability_read_dword
>
> pci_sysfs_init() is a late_initcall, and a driver may have already claimed
> one of these devices and enabled runtime power management for it, so the
> device could already be in D3hot by the time we get to pci_sysfs_init().
It also may be in D3cold if, say, AML can cut off power from it or ACPI
power resources can be used for that.
> The device itself should respond to the config read even while it's in
> D3hot, but if an upstream bridge is also in D3hot, the read won't even
> reach the device because the bridge won't forward it downstream to the
> device. If the bridge is a PCIe port, it should complete the read as an
> Unsupported Request, which may be reported to the CPU as an exception or as
> invalid data.
>
> Avoid this case by probing for reset support from pci_init_capabilities(),
> before a driver can claim the device. The device should be in D0 and fully
> accessible at that point.
>
> Signed-off-by: Bjorn Helgaas <bhelg...@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
> ---
> drivers/pci/pci-sysfs.c | 3 +--
> drivers/pci/probe.c | 3 +++
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index eb6bee8724cc..4933f0270471 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1542,11 +1542,10 @@ static int pci_create_capabilities_sysfs(struct
> pci_dev *dev)
> /* Active State Power Management */
> pcie_aspm_create_sysfs_dev_files(dev);
>
> - if (!pci_probe_reset_function(dev)) {
> + if (dev->reset_fn) {
> retval = device_create_file(&dev->dev, &reset_attr);
> if (retval)
> goto error;
> - dev->reset_fn = 1;
> }
> return 0;
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index ef5377438a1e..489660d0d384 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2121,6 +2121,9 @@ static void pci_init_capabilities(struct pci_dev *dev)
>
> /* Advanced Error Reporting */
> pci_aer_init(dev);
> +
> + if (pci_probe_reset_function(dev) == 0)
> + dev->reset_fn = 1;
> }
>
> /*
>
>
