On Wed, Nov 28, 2018 at 06:08:24PM -0600, Alexandru Gagniuc wrote:
> A warning is generated when a PCIe device is probed with a degraded
> link, but there was no similar mechanism to warn when the link becomes
> degraded after probing. The Link Bandwidth Notification provides this
> mechanism.
>
> Use the link bandwidth notification interrupt to detect bandwidth
> changes, and rescan the bandwidth, looking for the weakest point. This
> is the same logic used in probe().
I like the concept of this. What I don't like is the fact that it's
tied to pciehp, since I don't think the concept of Link Bandwidth
Notification is related to hotplug. So I think we'll only notice this
for ports that support hotplug. Maybe it's worth doing it this way
anyway, even if it could be generalized in the future?
> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@xxxxxxxxx>
> ---
> drivers/pci/hotplug/pciehp_hpc.c | 35 +++++++++++++++++++++++++++++++-
> 1 file changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 7dd443aea5a5..834672000b59 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -515,7 +515,8 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
> struct controller *ctrl = (struct controller *)dev_id;
> struct pci_dev *pdev = ctrl_dev(ctrl);
> struct device *parent = pdev->dev.parent;
> - u16 status, events;
> + struct pci_dev *endpoint;
> + u16 status, events, link_status;
>
> /*
> * Interrupts only occur in D3hot or shallower and only if enabled
> @@ -525,6 +526,17 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
> (!(ctrl->slot_ctrl & PCI_EXP_SLTCTL_HPIE) && !pciehp_poll_mode))
> return IRQ_NONE;
>
> + pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &link_status);
> +
> + if (link_status & PCI_EXP_LNKSTA_LBMS) {
> + if (pdev->subordinate && pdev->subordinate->self)
> + endpoint = pdev->subordinate->self;
> + else
> + endpoint = pdev;
> + __pcie_print_link_status(endpoint, false);
> + pcie_capability_write_word(pdev, PCI_EXP_LNKSTA, link_status);
> + }
> +
> /*
> * Keep the port accessible by holding a runtime PM ref on its parent.
> * Defer resume of the parent to the IRQ thread if it's suspended.
> @@ -677,6 +689,24 @@ static int pciehp_poll(void *data)
> return 0;
> }
>
> +static bool pcie_link_bandwidth_notification_supported(struct controller *ctrl)
> +{
> + int ret;
> + u32 cap;
> +
> + ret = pcie_capability_read_dword(ctrl_dev(ctrl), PCI_EXP_LNKCAP, &cap);
> + return (ret == PCIBIOS_SUCCESSFUL) && (cap & PCI_EXP_LNKCAP_LBNC);
> +}
> +
> +static void pcie_enable_link_bandwidth_notification(struct controller *ctrl)
> +{
> + u16 lnk_ctl;
> +
> + pcie_capability_read_word(ctrl_dev(ctrl), PCI_EXP_LNKCTL, &lnk_ctl);
> + lnk_ctl |= PCI_EXP_LNKCTL_LBMIE;
> + pcie_capability_write_word(ctrl_dev(ctrl), PCI_EXP_LNKCTL, lnk_ctl);
> +}
> +
> static void pcie_enable_notification(struct controller *ctrl)
> {
> u16 cmd, mask;
> @@ -713,6 +743,9 @@ static void pcie_enable_notification(struct controller *ctrl)
> pcie_write_cmd_nowait(ctrl, cmd, mask);
> ctrl_dbg(ctrl, "%s: SLOTCTRL %x write cmd %x\n", __func__,
> pci_pcie_cap(ctrl->pcie->port) + PCI_EXP_SLTCTL, cmd);
> +
> + if (pcie_link_bandwidth_notification_supported(ctrl))
> + pcie_enable_link_bandwidth_notification(ctrl);
> }
>
> static void pcie_disable_notification(struct controller *ctrl)
> --
> 2.17.1
>
