Re: [PATCH v1] PCI: pciehp: Fix the slot in BLINKINGON_STATE when Presence Detect Changed event occurred

[Lukas Wunner <lukas@wunner.de>]

On Mon, Apr 03, 2023 at 01:46:19PM +0800, Rongguang Wei wrote:
> When a Presence Detect Changed event has occurred, the slot status
> in either BLINKINGOFF_STATE or OFF_STATE, turn it off unconditionally.
> But if the slot status is in BLINKINGON_STATE and the slot is currently
> empty, the slot status was staying in BLINKINGON_STATE.
> 
> The message print like this:
>     pcieport 0000:00:01.5: pciehp: Slot(0-5): Attention button pressed
>     pcieport 0000:00:01.5: pciehp: Slot(0-5) Powering on due to button press
>     pcieport 0000:00:01.5: pciehp: Slot(0-5): Attention button pressed
>     pcieport 0000:00:01.5: pciehp: Slot(0-5): Button cancel
>     pcieport 0000:00:01.5: pciehp: Slot(0-5): Action canceled due to button press
> 
> It cause the next Attention Button Pressed event become Button cancel
> and missing the Presence Detect Changed event with this button press
> though this button presses event is occurred after 5s.

I see what you mean.

pciehp's behavior is incorrect if the Attention Button is pressed
on an unoccupied slot:

Upon a button press, pciehp_queue_pushbutton_work() is scheduled to run
after 5 seconds.  It synthesizes a Presence Detect Changed event,
whereupon pciehp_handle_presence_or_link_change() runs.

Should the slot be empty, pciehp_handle_presence_or_link_change() just
bails out and the state incorrectly remains in BLINKINGON_STATE.


> --- a/drivers/pci/hotplug/pciehp_ctrl.c
> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
> @@ -232,6 +232,7 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
>  	 */
>  	mutex_lock(&ctrl->state_lock);
>  	switch (ctrl->state) {
> +	case BLINKINGON_STATE:
>  	case BLINKINGOFF_STATE:
>  		cancel_delayed_work(&ctrl->button_work);
>  		fallthrough;

This solution has the disadvantage that a gratuitous "Card not present"
message is emitted even if the slot is occupied.

I'd prefer the following simpler solution:

diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index 529c348..e680444 100644
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -256,6 +256,7 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
 	present = pciehp_card_present(ctrl);
 	link_active = pciehp_check_link_active(ctrl);
 	if (present <= 0 && link_active <= 0) {
+		ctrl->state = POWEROFF_STATE;
 		mutex_unlock(&ctrl->state_lock);
 		return;
 	}

Optionally the assignment can be made conditional on
"if (ctrl->state == BLINKINGON_STATE)" for clarity.

Likewise, a "Card not present" message can optionally be emitted here.

Thanks,

Lukas