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.
