-----Original Message-----
From: Bjorn Helgaas <helg...@kernel.org>
Sent: Monday, October 7, 2019 6:24 AM
To: Dexuan Cui <de...@microsoft.com>
Cc: lorenzo.pieral...@arm.com; linux-...@vger.kernel.org; Michael Kelley
<mikel...@microsoft.com>; linux-hyp...@vger.kernel.org;
linux-ker...@vger.kernel.org; driverdev-devel@linuxdriverproject.org; Sasha
Levin <alexander.le...@microsoft.com>; Haiyang Zhang
<haiya...@microsoft.com>; KY Srinivasan <k...@microsoft.com>;
o...@aepfle.de; a...@canonical.com; jasow...@redhat.com; vkuznets
<vkuzn...@redhat.com>; marcelo.ce...@canonical.com; Stephen Hemminger
<sthem...@microsoft.com>; ja...@mellanox.com
Subject: Re: [PATCH v2] PCI: PM: Move to D0 before calling
pci_legacy_resume_early()
On Wed, Aug 14, 2019 at 01:06:55AM +0000, Dexuan Cui wrote:
In pci_legacy_suspend_late(), the device state is moved to PCI_UNKNOWN.
In pci_pm_thaw_noirq(), the state is supposed to be moved back to PCI_D0,
but the current code misses the pci_legacy_resume_early() path, so the
state remains in PCI_UNKNOWN in that path. As a result, in the resume
phase of hibernation, this causes an error for the Mellanox VF driver,
which fails to enable MSI-X because pci_msi_supported() is false due
to dev->current_state != PCI_D0:
mlx4_core a6d1:00:02.0: Detected virtual function - running in slave mode
mlx4_core a6d1:00:02.0: Sending reset
mlx4_core a6d1:00:02.0: Sending vhcr0
mlx4_core a6d1:00:02.0: HCA minimum page size:512
mlx4_core a6d1:00:02.0: Timestamping is not supported in slave mode
mlx4_core a6d1:00:02.0: INTx is not supported in multi-function mode,
aborting
PM: dpm_run_callback(): pci_pm_thaw+0x0/0xd7 returns -95
PM: Device a6d1:00:02.0 failed to thaw: error -95
To be more accurate, the "resume" phase means the "thaw" callbacks which
run before the system enters hibernation: when the user runs the command
"echo disk > /sys/power/state" for hibernation, first the kernel "freezes"
all the devices and creates a hibernation image, then the kernel "thaws"
the devices including the disk/NIC, writes the memory to the disk, and
powers down. This patch fixes the error message for the Mellanox VF driver
in this phase.
When the system starts again, a fresh kernel starts to run, and when the
kernel detects that a hibernation image was saved, the kernel "quiesces"
the devices, and then "restores" the devices from the saved image. In this
path:
device_resume_noirq() -> ... ->
pci_pm_restore_noirq() ->
pci_pm_default_resume_early() ->
pci_power_up() moves the device states back to PCI_D0. This path is
not broken and doesn't need my patch.
Signed-off-by: Dexuan Cui <de...@microsoft.com>
This looks like a bugfix for 5839ee7389e8 ("PCI / PM: Force devices to
D0 in pci_pm_thaw_noirq()") so maybe it should be marked for stable as
5839ee7389e8 was?
Rafael, could you confirm?