On Mon, Feb 22, 2016 at 01:05:48PM -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 1000ms, testing
> every 100ms whether the second dword of config space is read as -1.
>
> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Applied to pci/virtualization for v4.6, thanks, Alex!
> ---
> v3: Read 2nd dword since SR-IOV VFs don't implement the 1st dword
> v2: Change loop to incorporate initial 100ms delay, replace delay in
> callee functions, add comment.
>
> drivers/pci/pci.c | 27 +++++++++++++++++++++++++--
> 1 file changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 602eb42..365ac76 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3414,6 +3414,29 @@ int pci_wait_for_pending_transaction(struct pci_dev *dev)
> }
> EXPORT_SYMBOL(pci_wait_for_pending_transaction);
>
> +/*
> + * We should only need to wait 100ms after FLR, but some devices take longer.
> + * Wait for up to 1000ms for config space to return something other than -1.
> + * Intel IGD requires this when an LCD panel is attached. We read the 2nd
> + * dword because VFs don't implement the 1st dword.
> + */
> +static void pci_flr_wait(struct pci_dev *dev)
> +{
> + int i = 0;
> + u32 id;
> +
> + do {
> + msleep(100);
> + pci_read_config_dword(dev, PCI_COMMAND, &id);
> + } while (i++ < 10 && id == ~0);
> +
> + if (id == ~0)
> + dev_warn(&dev->dev, "Failed to return from FLR\n");
> + else if (i > 1)
> + dev_info(&dev->dev, "Required additional "
> + "%dms to return from FLR\n", (i - 1) * 100);
> +}
> +
> static int pcie_flr(struct pci_dev *dev, int probe)
> {
> u32 cap;
> @@ -3429,7 +3452,7 @@ static int pcie_flr(struct pci_dev *dev, int probe)
> dev_err(&dev->dev, "timed out waiting for pending transaction; performing function level reset anyway\n");
>
> pcie_capability_set_word(dev, PCI_EXP_DEVCTL, PCI_EXP_DEVCTL_BCR_FLR);
> - msleep(100);
> + pci_flr_wait(dev);
> return 0;
> }
>
> @@ -3459,7 +3482,7 @@ static int pci_af_flr(struct pci_dev *dev, int probe)
> dev_err(&dev->dev, "timed out waiting for pending transaction; performing AF function level reset anyway\n");
>
> pci_write_config_byte(dev, pos + PCI_AF_CTRL, PCI_AF_CTRL_FLR);
> - msleep(100);
> + pci_flr_wait(dev);
> return 0;
> }
>
>
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