Hi Alex, On Fri, Feb 12, 2016 at 04:51:08PM -0700, Alex Williamson wrote: > Some devices take longer than the spec indicates to return from FLR > reset, a notable case of this is Intel integrated graphics (IGD), > which can often take an additional 300ms powering down an attached > LCD panel as part of the FLR. Allow devices up to an additional > 1000ms, testing every 100ms whether the first dword of config space > is read as -1.
This gives me a little more heartburn about ignoring presence detect during reset and pretending that the post-reset device is the same as the pre-reset device. I suspect this problem wouldn't occur if we just watched for a new device to show up after the FLR, because we wouldn't have a timeout at all. But given that this *is* the way we do it, ... > Signed-off-by: Alex Williamson <[email protected]> > --- > > Copying KVM list as this patch is required for IGD assignment. > > drivers/pci/pci.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 602eb42..3b90a42 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -3414,6 +3414,25 @@ int pci_wait_for_pending_transaction(struct pci_dev > *dev) > } > EXPORT_SYMBOL(pci_wait_for_pending_transaction); > > +static void pci_wait_alive(struct pci_dev *dev) > +{ > + int i; > + u32 id; > + > + for (i = 0; i < 10; i++) { > + pci_read_config_dword(dev, PCI_VENDOR_ID, &id); > + if (~id != 0) { > + if (i > 0) > + dev_info(&dev->dev, "Required additional %d" > + "ms to return from reset\n", i * 100); > + return; > + } > + msleep(100); > + } > + > + dev_warn(&dev->dev, "Failed to return from reset\n"); > +} > + > static int pcie_flr(struct pci_dev *dev, int probe) > { > u32 cap; > @@ -3430,6 +3449,7 @@ static int pcie_flr(struct pci_dev *dev, int probe) > > pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_BCR_FLR); > msleep(100); > + pci_wait_alive(dev); Can we fold the msleep() into pci_wait_alive(), so all the delay happens in one place? Maybe you can add a comment to the effect that the spec says devices should be ready 100ms after FLR, but some devices take longer. > return 0; > } > > @@ -3460,6 +3480,7 @@ static int pci_af_flr(struct pci_dev *dev, int probe) > > pci_write_config_byte(dev, pos + PCI_AF_CTRL, PCI_AF_CTRL_FLR); > msleep(100); > + pci_wait_alive(dev); > return 0; > } > >
