On Mon, Aug 23, 2021 at 12:49:19PM -0600, Derrick, Jonathan wrote:
> From: James Puthukattukaran <james.puthukattukaran@xxxxxxxxxx>
>
> When a specific x8 CEM card is bifurcated into x4x4 mode, and the
> upstream ports both support hotplugging on each respective x4 device, a
> slot management system for the CEM card requires both x4 devices to be
> sysfs removed from the OS before it can safely turn-off physical power.
sysfs removed from the OS seems a bit confusing.. Do you mean removed via
sysfs by echo 0 > power?
> The implications are that Slot Control will display Powered Off status
> for the device where the device is actually powered until both ports
> have powered off.
>
> When power is removed from the first half, real power and link remains
> active while waiting for the second half to have power removed. When
> power is then removed from the second half, the first half starts
> shutdown sequence and will trigger a DLLSC event. This is misinterpreted
> as an enabling event and causes the first half to be re-enabled.
>
> The spurious enable can be resolved by ignoring link status change
> events when no link is active when in the off state. This patch adds a
> quirk for the card.
>
> Acked-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
> Signed-off-by: James Puthukattukaran <james.puthukattukaran@xxxxxxxxxx>
> ---
> v1->v2: Device-specific quirk
>
> drivers/pci/hotplug/pciehp_ctrl.c | 7 +++++++
> drivers/pci/quirks.c | 30 ++++++++++++++++++++++++++++++
> include/linux/pci.h | 1 +
> 3 files changed, 38 insertions(+)
>
> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
> index 529c34808440..db41f78bfac8 100644
> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -225,6 +225,7 @@ void pciehp_handle_disable_request(struct controller *ctrl)
> void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
> {
> int present, link_active;
> + struct pci_dev *pdev = ctrl->pcie->port;
>
> /*
> * If the slot is on and presence or link has changed, turn it off.
> @@ -265,6 +266,12 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
> cancel_delayed_work(&ctrl->button_work);
> fallthrough;
> case OFF_STATE:
> + if (pdev->shared_pcc_and_link_slot &&
> + (events & PCI_EXP_SLTSTA_DLLSC) && !link_active) {
Is it !link_active? Based on the explanation, until we turn off both slots
you would see link is still active correct?
> + mutex_unlock(&ctrl->state_lock);
> + break;
> + }
> +
