[+cc Rafael, linux-pm]
On Mon, Sep 23, 2013 at 1:36 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 23 Sep 2013, Andy Lutomirski wrote:
>
>> I've been getting this on several recent kernel revisions. Is it
>> interesting? If so, I'm happy to help diagnose it. If not, can the
>> message be killed or severely ratelimited? I'm getting so much of
>> this that it tends to overflow the log ring.
>
> It's interesting only if you care about when your EHCI controllers get
> resumed and suspended. In this case, it's not clear why the
> transitions happen so rapidly. It looks like some sort of polling
> is going on at roughly 2-second intervals.
>
>> [ 287.344991] ehci-pci 0000:00:1d.0: power state changed by ACPI to D0
>> [ 287.445433] ehci-pci 0000:00:1d.0: setting latency timer to 64
>> [ 287.446255] ehci-pci 0000:00:1a.0: power state changed by ACPI to D0
>> [ 287.456094] ehci-pci 0000:00:1d.0: power state changed by ACPI to D3cold
>> [ 287.547205] ehci-pci 0000:00:1a.0: setting latency timer to 64
>> [ 287.557890] ehci-pci 0000:00:1a.0: power state changed by ACPI to D3cold
>> [ 290.126910] ehci-pci 0000:00:1d.0: power state changed by ACPI to D0
>> [ 290.227958] ehci-pci 0000:00:1d.0: setting latency timer to 64
>> [ 290.228416] ehci-pci 0000:00:1a.0: power state changed by ACPI to D0
>> [ 290.238749] ehci-pci 0000:00:1d.0: power state changed by ACPI to D3cold
>> [ 290.328904] ehci-pci 0000:00:1a.0: setting latency timer to 64
>> [ 290.339565] ehci-pci 0000:00:1a.0: power state changed by ACPI to D3cold
>> [ 292.214834] ehci-pci 0000:00:1d.0: power state changed by ACPI to D0
>> [ 292.315458] ehci-pci 0000:00:1d.0: setting latency timer to 64
>> [ 292.315908] ehci-pci 0000:00:1a.0: power state changed by ACPI to D0
>> [ 292.326262] ehci-pci 0000:00:1d.0: power state changed by ACPI to D3cold
>> [ 292.416487] ehci-pci 0000:00:1a.0: setting latency timer to 64
>> [ 292.431075] ehci-pci 0000:00:1a.0: power state changed by ACPI to D3cold
>> [ 295.458048] ehci-pci 0000:00:1d.0: power state changed by ACPI to D0
>> [ 295.558613] ehci-pci 0000:00:1d.0: setting latency timer to 64
>
> This question should be addressed to the PCI mailing list (cc'ed), as
> those two messages are generated by
> drivers/pci/pci-acpi.c:acpi_pci_set_power_state() and
> drivers/pci/pci.c:pcibios_set_master() respectively.
d010e5769 ("PCI / ACPI: Use dev_dbg() instead of dev_info() in
acpi_pci_set_power_state()") might be part of the solution. That was
done in response to https://bugzilla.kernel.org/show_bug.cgi?id=60636,
which looks basically the same as your complaint.
But if we are indeed polling every two seconds, even a dev_dbg() seems
like overkill to me. Rafael or Lan can probably provide a better
answer here.
As for the "setting latency timer" messages, I really doubt those are
useful to anybody. If nobody objects, I'll just drop it, e.g.:
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b821a62..55a947b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2854,7 +2854,7 @@ void __weak pcibios_set_master(struct pci_dev *dev)
lat = pcibios_max_latency;
else
return;
- dev_printk(KERN_DEBUG, &dev->dev, "setting latency timer to %d\n", lat);
+
pci_write_config_byte(dev, PCI_LATENCY_TIMER, lat);
}
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