On Wed, May 04, 2022 at 02:59:17PM +0200, Rafael J. Wysocki wrote:
> On Tue, May 3, 2022 at 7:59 PM Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
> >
> > Hi Rafael,
> >
> > On Thu, Apr 14, 2022 at 03:11:21PM +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > >
> > > There are some issues related to changing power states of PCI
> > > devices, mostly related to carrying out unnecessary actions in some
> > > places, and the code is generally hard to follow.
> > >
> > > 1. pci_power_up() has two callers, pci_set_power_state() and
> > > pci_pm_default_resume_early(). The latter updates the current
> > > power state of the device right after calling pci_power_up()
> > > and it restores the entire config space of the device right
> > > after that, so pci_power_up() itself need not read the
> > > PCI_PM_CTRL register or restore the BARs after programming the
> > > device into D0 in that case.
> > >
> > > 2. It is generally hard to get a clear view of the pci_power_up()
> > > code flow, especially in some corner cases, due to all of the
> > > involved PCI_PM_CTRL register reads and writes occurring in
> > > pci_platform_power_transition() and in pci_raw_set_power_state(),
> > > some of which are redundant.
> > >
> > > 3. The transitions from low-power states to D0 and the other way
> > > around are unnecessarily tangled in pci_raw_set_power_state()
> > > which causes it to use a redundant local variable and makes it
> > > rather hard to follow.
> > >
> > > To address the above shortcomings, make the following changes:
> > >
> > > a. Remove the code handling transitions into D0
> > > from pci_raw_set_power_state() and rename it as
> > > pci_set_low_power_state().
> > >
> > > b. Add the code handling transitions into D0 directly
> > > to pci_power_up() and to a new wrapper function
> > > pci_set_full_power_state() calling it internally that is
> > > only used in pci_set_power_state().
> > >
> > > c. Make pci_power_up() avoid redundant PCI_PM_CTRL register reads
> > > and make it work in the same way for transitions from any
> > > low-power states (transitions from D1 and D2 are handled
> > > slightly differently before the change).
> > >
> > > d. Put the restoration of the BARs and the PCI_PM_CTRL
> > > register read confirming the power state change into
> > > pci_set_full_power_state() to avoid doing that in
> > > pci_pm_default_resume_early() unnecessarily.
> > >
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > > Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> >
> > This change as commit 5bffe4c611f5 ("PCI/PM: Rework changing power
> > states of PCI devices") causes my AMD-based system to fail to fully
> > boot. As far as I can tell, this might be NVMe related, which might make
> > getting a full log difficult, as journalctl won't have anywhere to save
> > it. I see:
> >
> > nvme nvme0: I/O 8 QID 0 timeout, completion polled
> >
> > then shortly afterwards:
> >
> > nvme nvme0: I/O 24 QID 0 timeout, completion polled
> > nvme nvme0: missing or invalid SUBNQN field
> >
> > then I am dropped into an emergency shell.
>
> Thanks for the report!
>
> > This is a log from the previous commit, which may give some hints about
> > the configuration of this particular system.
> >
> > https://gist.github.com/nathanchance/8a56f0939410cb187896e904c72e41e7/raw/b47b2620bdd32d43c7a3b209fcfd9e3d4668f058/good-boot.log
> >
> > If there is any additional debugging information I can provide or
> > patches I can try, please let me know!
>
> Please see what happens if the "if (dev->current_state == PCI_D0)"
> check and the following "return 0" statement in pci_power_up() are
> commented out.
If I understand you correctly, this? Unfortunately, that does not help.
Cheers,
Nathan
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 1e22dc5187e7..9f7a463107f3 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1235,8 +1235,10 @@ int pci_power_up(struct pci_dev *dev)
}
/* There's nothing more to do if current_state is D0 at this point. */
+#if 0
if (dev->current_state == PCI_D0)
return 0;
+#endif
/*
* Program the device into PCI_D0 by forcing the entire word to 0 (this
