On Tue, Nov 13, 2018 at 03:57:47PM +0000, Shameerali Kolothum Thodi wrote:
> > The smb_mb() thing is not that clear (at least to me) because it is used
> > in two places in the driver and both seem to be making write to
> > ctrl->cmd_busy visible to other CPUs but I don't see where we deal with
> > the read part.
> >
> > I may be missing something, though.
>
> I think the read part is in wait_event_timeout() which evaluates the condition.
> The wake_up is called from the pciehp_isr(). Since the flag is being updated
> in both process level and interrupt handler context, smp_mb() is used. I think
> the same now applies to ctrl->slot_ctrl now as this being used in process
> context and interrupt context as well.
Right, but that would require to use another read/general barrier in the
pciehp_isr() before we read the variable in case interrupt happens
immediately on another CPU (at least that's my understanding). Since I'm
not too comfortable with all these barriers to be honest I would prefer
reading the slot control register directly in pciehp_isr() :-)
I wonder if the below works in your case? I think it is still easier to
understand than adding another barrier there.
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 7dd443aea5a5..575da1005836 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -518,11 +518,9 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
u16 status, events;
/*
- * Interrupts only occur in D3hot or shallower and only if enabled
- * in the Slot Control register (PCIe r4.0, sec 6.7.3.4).
+ * Interrupts only occur in D3hot or shallower (PCIe r4.0, sec 6.7.3.4).
*/
- if (pdev->current_state == PCI_D3cold ||
- (!(ctrl->slot_ctrl & PCI_EXP_SLTCTL_HPIE) && !pciehp_poll_mode))
+ if (pdev->current_state == PCI_D3cold)
return IRQ_NONE;
/*
@@ -548,6 +546,22 @@ static irqreturn_t pciehp_isr(int irq, void *dev_id)
return IRQ_NONE;
}
+ if (!pciehp_poll_mode) {
+ u16 ctrl;
+
+ /*
+ * Check that the hotplug interrupt was enabled. It may
+ * be that the interrupt was meant for PME instead as
+ * they share the MSI vector.
+ */
+ pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &ctrl);
+ if (ctrl == (u16) ~0 || !(ctrl & PCI_EXP_SLTCTL_HPIE)) {
+ if (parent)
+ pm_runtime_put(parent);
+ return IRQ_NONE;
+ }
+ }
+
/*
* Slot Status contains plain status bits as well as event
* notification bits; right now we only want the event bits.
