Re: [PATCH] PCI/ASPM: Don't retrain link if ASPM not possible.

Bjorn Helgaas
2016-12-08T20:47:49Z

On Thu, Nov 17, 2016 at 02:25:01PM -0800, David Daney wrote:
> From: David Daney <david.daney@cavium.com>
>
> Some (defective) PCIe devices are not able to reliably do link
> retraining.
>
> Check to see if ASPM is possible between link partners before
> configuring common clocking, and doing the resulting link retraining.
> If ASPM is not possible, there is no reason to risk losing access to a
> device due to an unnecessary link retraining.
>
> Signed-off-by: David Daney <david.daney@cavium.com>

Applied to pci/aspm for v4.10, thanks, David!

> ---
> drivers/pci/pcie/aspm.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 0ec649d..d6667db 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -351,12 +351,26 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
> return;
> }
>
> + /* Get upstream/downstream components' register state */
> + pcie_get_aspm_reg(parent, &upreg);
> + child = list_entry(linkbus->devices.next, struct pci_dev, bus_list);
> + pcie_get_aspm_reg(child, &dwreg);
> +
> + /*
> + * If ASPM not supported, don't mess with the clocks and link,
> + * bail out now.
> + */
> + if (!(upreg.support & dwreg.support))
> + return;
> +
> /* Configure common clock before checking latencies */
> pcie_aspm_configure_common_clock(link);
>
> - /* Get upstream/downstream components' register state */
> + /*
> + * Re-read upstream/downstream components' register state
> + * after clock configuration
> + */
> pcie_get_aspm_reg(parent, &upreg);
> - child = list_entry(linkbus->devices.next, struct pci_dev, bus_list);
> pcie_get_aspm_reg(child, &dwreg);
>
> /*
> --
> 1.7.11.7
>
> --
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