On Wed, May 4, 2022 at 7:03 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>
> [+cc Anders]
>
> On Tue, May 03, 2022 at 10:59:43AM -0700, Nathan Chancellor wrote:
> > 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.
>
> I dropped 5bffe4c611f5 and subsequent pci/pm patches temporarily while
> this gets worked out.
OK
It looks like I missed something subtle that triggers on a subset of
systems only.
