On Tue, Mar 10, 2020 at 01:21:00PM -0500, Stuart Hayes wrote:
> When a pciehp slot is powered down via /sys/bus/pci/slots/<slot>/power,
> and then the card is physically removed, the kernel will sometimes try to
> enable the slot as the card is removed, which results in an error in the
> kernel log.
>
> This can happen if the presence detect and link active bits don't go down
> at the exact same time. When the card is disabled via /sys/.../power, the
> card is placed in OFF_STATE, but the presence detect and link active bits
> can still be up. Then, when, say, presence detect goes down, an interrupt
> reports that the presence detect has changed, and the code in
> pciehp_handle_presence_or_link_change() will see that the link is up
> (because it hasn't gone down yet), and it will try to enable the slot.
>
> This patch modifies that code so it won't try to enable a slot in OFF_STATE
> unless it sees the presence detect changed bit with presence detect active,
> or the link status changed bit with an active link. This will prevent the
> unwanted attempts to enable a card that's being removed, but will still
> allow the slot to come up if the slot is re-enabled by writing to
> /sys/.../power, or if a new card is added to the slot.
Looking for a reviewed-by from Lukas for this.
> Signed-off-by: Stuart Hayes <stuart.w.hayes@xxxxxxxxx>
> ---
> drivers/pci/hotplug/pciehp_ctrl.c | 24 ++++++++++++++----------
> 1 file changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
> index 6503d15effbb..f6cbf21711e0 100644
> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -267,16 +267,20 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
> cancel_delayed_work(&ctrl->button_work);
> /* fall through */
> case OFF_STATE:
> - ctrl->state = POWERON_STATE;
> - mutex_unlock(&ctrl->state_lock);
> - if (present)
> - ctrl_info(ctrl, "Slot(%s): Card present\n",
> - slot_name(ctrl));
> - if (link_active)
> - ctrl_info(ctrl, "Slot(%s): Link Up\n",
> - slot_name(ctrl));
> - ctrl->request_result = pciehp_enable_slot(ctrl);
> - break;
> + if ((events & PCI_EXP_SLTSTA_PDC && present) ||
> + (events & PCI_EXP_SLTSTA_DLLSC && link_active)) {
> + ctrl->state = POWERON_STATE;
> + mutex_unlock(&ctrl->state_lock);
> + if (present)
> + ctrl_info(ctrl, "Slot(%s): Card present\n",
> + slot_name(ctrl));
> + if (link_active)
> + ctrl_info(ctrl, "Slot(%s): Link Up\n",
> + slot_name(ctrl));
> + ctrl->request_result = pciehp_enable_slot(ctrl);
> + break;
> + }
> + /* fall through */
> default:
> mutex_unlock(&ctrl->state_lock);
> break;
> --
> 2.18.1
>
