Re: [PATCH RFC v2 2/4] PCI: pciehp: Do not turn off slot if presence comes up after link

Lukas Wunner
2019-02-21T07:36:38Z

On Tue, Feb 19, 2019 at 07:20:28PM -0600, Alexandru Gagniuc wrote:
> @@ -213,6 +213,21 @@ void pciehp_handle_disable_request(struct controller *ctrl)
> ctrl->request_result = pciehp_disable_slot(ctrl, SAFE_REMOVAL);
> }
>
> +static bool is_delayed_presence_up_event(struct controller *ctrl, u32 events)
> +{
> + bool present, link_active;
> +
> + if (!ctrl->inband_presence_disabled)
> + return false;
> +
> + present = pciehp_card_present(ctrl);
> + link_active = pciehp_check_link_active(ctrl);
> +
> + if (!present || !link_active || events & PCI_EXP_SLTSTA_DLLSC)
> + return false;
> +
> + return true;
> +}
> void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)

Newline please after the closing curly brace.

> @@ -220,13 +235,22 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
> /*
> * If the slot is on and presence or link has changed, turn it off.
> * Even if it's occupied again, we cannot assume the card is the same.
> + * When the card is swapped, we also expect a change in link state,
> + * without which, it's likely presence became high after link-active.
> */

Maybe it's just me but I find the code comment difficult to understand.
How about something along the lines of:

/*
* If the slot is on and presence or link has changed, turn it off.
* Even if it's occupied again, we cannot assume the card is the same.
+ *
+ * An exception is a delayed "Card present" after a "Link Up".
+ * This can happen on controllers with in-band presence disabled,
+ * PCIe r5.0 sec X.Y.Z.
*/

> mutex_lock(&ctrl->state_lock);
> + present = pciehp_card_present(ctrl);
> + link_active = pciehp_check_link_active(ctrl);
> switch (ctrl->state) {

These two assignments appear to be superfluous as you're also performing
them in pciehp_check_link_active().

Thanks,

Lukas