Re: [PATCH] PCI/PM: Put devices to low power state on shutdown
From: Kai-Heng Feng
Date: Fri Oct 04 2024 - 05:28:12 EST
On 2024/10/4 12:33 PM, Chia-Lin Kao (AceLan) wrote:
On Wed, Sep 11, 2024 at 02:38:20PM -0500, Mario Limonciello wrote:
On 9/11/2024 14:16, Mario Limonciello wrote:
On 9/11/2024 14:05, Bjorn Helgaas wrote:
On Fri, Jul 12, 2024 at 02:24:11PM +0800, Kai-Heng Feng wrote:
Some laptops wake up after poweroff when HP Thunderbolt Dock G4 is
connected.
The following error message can be found during shutdown:
pcieport 0000:00:1d.0: AER: Correctable error message received
from 0000:09:04.0
pcieport 0000:09:04.0: PCIe Bus Error: severity=Correctable,
type=Data Link Layer, (Receiver ID)
pcieport 0000:09:04.0: device [8086:0b26] error
status/mask=00000080/00002000
pcieport 0000:09:04.0: [ 7] BadDLLP
Calling aer_remove() during shutdown can quiesce the error message,
however the spurious wakeup still happens.
The issue won't happen if the device is in D3 before system shutdown, so
putting device to low power state before shutdown to solve the issue.
I don't have a sniffer so this is purely guesswork, however I believe
putting device to low power state it's the right thing to do.
My objection here is that we don't have an explanation of why this
should matter or a pointer to any spec language about this situation,
so it feels a little bit random.
I suppose the problem wouldn't happen if AER interrupts were disabled?
We already do disable them in aer_suspend(), but maybe that's not used
in the shutdown path?
My understanding is that .shutdown() should turn off device interrupts
and stop DMA. So maybe we need an aer_shutdown() that disables
interrupts?
IMO I see this commit as two problems with the same solution.
I don't doubt that cleaning up AER interrupts in the shutdown path would
help AER messages, but you really don't "want" devices to be in D0 when
the system is "off" because even if the system is off some rails are
still active and the device might still be powered.
A powered device could cause interrupts (IE a spurious wakeup).
It's a bit of a stretch, but ACPI 7.4.2.5 and 7.4.2.6 are the closest
corollary to a spec I can find.
"Devices states are compatible with the current Power Resource states. In
other words, all devices are in the D3 state when the system state is S4."
https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/07_Power_and_Performance_Mgmt/oem-supplied-system-level-control-methods.html
Hi,
I'd like to revive this thread and support this description from the
ACPI spec.
In ACPI 7.4.2.5, it states: "All devices are in the D3 state when the
system state is S4," and in ACPI 7.4.2.6, it says: "The S5 state is
similar to the S4 state except that OSPM does not save any context."
I believe this implies that devices should also be in D3 when the
system is in S5.
Sorry for the belated response.
I think AceLan found a better explanation on why this patch is needed.
I can resend the patch with modified message if Bjorn agrees.
Kai-Heng
Link: https://bugzilla.kernel.org/show_bug.cgi?id=219036
Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
---
drivers/pci/pci-driver.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index af2996d0d17f..4c6f66f3eb54 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -510,6 +510,14 @@ static void pci_device_shutdown(struct device *dev)
if (drv && drv->shutdown)
drv->shutdown(pci_dev);
+ /*
+ * If driver already changed device's power state, it can mean the
+ * wakeup setting is in place, or a workaround is used.
Hence keep it
+ * as is.
+ */
+ if (!kexec_in_progress && pci_dev->current_state == PCI_D0)
+ pci_prepare_to_sleep(pci_dev);
+
/*
* If this is a kexec reboot, turn off Bus Master bit on the
* device to tell it to not continue to do DMA. Don't touch
--
2.43.0