On 2/9/20 2:25 PM, Lukas Wunner wrote:
> On Sun, Feb 09, 2020 at 07:07:22PM +0100, Lukas Wunner wrote:
>> Actually, scratch that. After thinking about this problem for a day
>> I've come up with a much simpler and more elegant solution. Could you
>> test if the below works for you?
>
> Sorry, I missed a few things:
>
> * pm_runtime_put() is called too often in the MSI case.
> * If only the CC bit is set or if ignore_hotplug is set, the function
> may return prematurely without re-reading the Slot Status register.
> * Returning IRQ_NONE in the MSI case even though the IRQ thread was woken
> may incorrectly signal a spurious interrupt to the genirq code.
> It's better to return IRQ_HANDLED instead.
>
> Below is another attempt. I'll have to take a look at this with a
> fresh pair of eyeballs though to verify I haven't overlooked anything
> else and also to determine if this is actually simpler than Stuart's
> approach. Again, the advantage here is that processing of the events
> by the IRQ thread is sped up by not delaying it until the Slot Status
> register has settled.
>
> Thanks.
>
> -- >8 --
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index c3e3f53..db5baa5 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -530,6 +530,7 @@ 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;
> + irqreturn_t ret = IRQ_NONE;
> u16 status, events;
>
> /*
> @@ -553,6 +554,7 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
> }
> }
>
> +read_status:
> pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status);
> if (status == (u16) ~0) {
> ctrl_info(ctrl, "%s: no response from device\n", __func__);
> @@ -579,13 +581,11 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
> if (!events) {
> if (parent)
> pm_runtime_put(parent);
> - return IRQ_NONE;
> + return ret;
> }
>
> pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, events);
> ctrl_dbg(ctrl, "pending interrupts %#06x from Slot Status\n", events);
> - if (parent)
> - pm_runtime_put(parent);
>
> /*
> * Command Completed notifications are not deferred to the
> @@ -595,21 +595,33 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
> ctrl->cmd_busy = 0;
> smp_mb();
> wake_up(&ctrl->queue);
> -
> - if (events == PCI_EXP_SLTSTA_CC)
> - return IRQ_HANDLED;
> -
> events &= ~PCI_EXP_SLTSTA_CC;
> }
>
> if (pdev->ignore_hotplug) {
> ctrl_dbg(ctrl, "ignoring hotplug event %#06x\n", events);
> - return IRQ_HANDLED;
> + events = 0;
> }
>
> /* Save pending events for consumption by IRQ thread. */
> atomic_or(events, &ctrl->pending_events);
> - return IRQ_WAKE_THREAD;
> +
> + /*
> + * In MSI mode, all event bits must be zero before the port will send
> + * a new interrupt (PCIe Base Spec r5.0 sec 6.7.3.4). So re-read the
> + * Slot Status register in case a bit was set between read and write.
> + */
> + if (pci_dev_msi_enabled(pdev) && !pciehp_poll_mode) {
> + irq_wake_thread(irq, ctrl);
> + ret = IRQ_HANDLED;
> + goto read_status;
> + }
> +
> + if (parent)
> + pm_runtime_put(parent);
> + if (events)
> + return IRQ_WAKE_THREAD;
> + return IRQ_HANDLED;
> }
>
> static irqreturn_t pciehp_ist(int irq, void *dev_id)
>
I tested this patch, and it fixes the issue on my system.
