Messages in this thread | | | Date | Sat, 02 Feb 2013 16:12:03 +0400 | From | Konstantin Khlebnikov <> | Subject | Re: [PATCH 3/5] PCI: revert preparing for wakeup in runtime-suspend finalization |
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Rafael J. Wysocki wrote: > On Tuesday, January 29, 2013 12:55:15 PM Rafael J. Wysocki wrote: >> On Tuesday, January 29, 2013 11:04:57 AM Konstantin Khlebnikov wrote: >>> Rafael J. Wysocki wrote: >>>> On Monday, January 28, 2013 04:17:42 PM Bjorn Helgaas wrote: >>>>> [+cc Rafael] >>>>> >>>>> On Fri, Jan 18, 2013 at 4:42 AM, Konstantin Khlebnikov >>>>> <khlebnikov@openvz.org> wrote: >>>>>> This patch effectively reverts commit 42eca2302146fed51335b95128e949ee6f54478f >>>>>> ("PCI: Don't touch card regs after runtime suspend D3") >>>>>> >>>>>> | This patch checks whether the pci state is saved and doesn't attempt to hit >>>>>> | any registers after that point if it is. >>>>>> >>>>>> This seems completely wrong. Yes, PCI configuration space has been saved by >>>>>> driver, but this doesn't means that all job is done and device has been >>>>>> suspended and ready for waking up in the future. >>>>>> >>>>>> For example driver e1000e for ethernet in my thinkpad x220 saves pci-state >>>>>> but device cannot wakeup after that, because it needs some ACPI callbacks >>>>>> which usually called from pci_finish_runtime_suspend(). >>>>>> >>>>>> | Optimus (dual-gpu) laptops seem to have their own form of D3cold, but >>>>>> | unfortunately enter it on normal D3 transitions via the ACPI callback. >>>>>> >>>>>> Hardware which disappears from the bus unexpectedly is exception, so let's >>>>>> handle it as an exception. Its driver should set device state to D3cold and >>>>>> the rest code will handle it properly. >>>>> >>>>> Functions in D3cold don't have power, so it's completely expected that >>>>> they would disappear from the bus and not respond to config accesses. >>>>> Maybe Dave was referring to D3hot, where functions *should* respond to >>>>> config accesses. I dunno. >>>>> >>>>> Just to be clear, it sounds like 42eca230 caused a regression on your >>>>> e1000e device? If so, I guess we should revert it unless you and Dave >>>>> can figure out a better patch that fixes both your e1000e device and >>>>> the Optimus issue. >>>> >>>> Yes, if there's a regression, let's revert it, but I'd like the regression >>>> to be described clearly. >>> >>> Yep, this is regression. >>> >>> commit 42eca2302146fed51335b95128e949ee6f54478f ("PCI: Don't touch >>> card regs after runtime suspend D3") changes state convention during >>> runtime-suspend transaction too much. If PCI configuration space >>> has been saved by driver that does not means that all job is done >>> and device has been suspended and ready for waking up in the future. >>> >>> e1000e saves pci-config space itself, but it requires operations which >>> pci_finish_runtime_suspend() does: preparing for wake (calling particular >>> platform pm-callbacks) and switching to proper sleep state. >> >> Well, I'd argue this is a bug in e1000e. Why does it need to save the PCI >> config space even though pci_pm_runtime_suspend() will do that anyway? > > I honestly don't think we should revert 42eca2302146 because of this. > > Yes, there is a requirement that drivers not save the PCI config space by > themselves unless they want to do the whole power management by themselves too > and e1000e is not following that. So either we need to drop the > pci_save_state() from __e1000_shutdown() which I would prefer (I'm not really > sure why it is there), or e1000_runtime_suspend() needs to call > pci_finish_runtime_suspend() by itself.
Yet another problem: some drivers calls pci_save_state() from ->probe() callback to use this saved state in pci_error_handlers->slot_reset(). As result pdev->state_saved is true mostly all time. At least e1000e and drivers/pci/pcie/portdrv_pci.c are doing this.
I think it will be safer to revert 42eca2302146 in v3.8
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