On Wednesday, September 18, 2019 6:52:31 PM CEST mario.limoncie...@dell.com wrote: > > -----Original Message----- > > From: Rafael J. Wysocki <r...@rjwysocki.net> > > Sent: Tuesday, September 17, 2019 4:36 PM > > To: Keith Busch > > Cc: Limonciello, Mario; Jens Axboe; Christoph Hellwig; Sagi Grimberg; linux- > > n...@lists.infradead.org; LKML; Hong, Ryan; Wang, Crag; s...@google.com; > > Dominguez, Jared > > Subject: Re: [PATCH] nvme-pci: Save PCI state before putting drive into > > deepest > > state > > > > > > [EXTERNAL EMAIL] > > > > On Tuesday, September 17, 2019 11:24:14 PM CEST Keith Busch wrote: > > > On Wed, Sep 11, 2019 at 06:42:33PM -0500, Mario Limonciello wrote: > > > > The action of saving the PCI state will cause numerous PCI configuration > > > > space reads which depending upon the vendor implementation may cause > > > > the drive to exit the deepest NVMe state. > > > > > > > > In these cases ASPM will typically resolve the PCIe link state and APST > > > > may resolve the NVMe power state. However it has also been observed > > > > that this register access after quiesced will cause PC10 failure > > > > on some device combinations. > > > > > > > > To resolve this, move the PCI state saving to before SetFeatures has > > > > been > > > > called. This has been proven to resolve the issue across a 5000 sample > > > > test on previously failing disk/system combinations. > > > > > > > > Signed-off-by: Mario Limonciello <mario.limoncie...@dell.com> > > > > --- > > > > drivers/nvme/host/pci.c | 13 +++++++------ > > > > 1 file changed, 7 insertions(+), 6 deletions(-) > > > > > > > > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c > > > > index 732d5b6..9b3fed4 100644 > > > > --- a/drivers/nvme/host/pci.c > > > > +++ b/drivers/nvme/host/pci.c > > > > @@ -2894,6 +2894,13 @@ static int nvme_suspend(struct device *dev) > > > > if (ret < 0) > > > > goto unfreeze; > > > > > > > > + /* > > > > + * A saved state prevents pci pm from generically controlling > > > > the > > > > + * device's power. If we're using protocol specific settings, > > > > we don't > > > > + * want pci interfering. > > > > + */ > > > > + pci_save_state(pdev); > > > > + > > > > ret = nvme_set_power_state(ctrl, ctrl->npss); > > > > if (ret < 0) > > > > goto unfreeze; > > > > @@ -2908,12 +2915,6 @@ static int nvme_suspend(struct device *dev) > > > > ret = 0; > > > > goto unfreeze; > > > > } > > > > - /* > > > > - * A saved state prevents pci pm from generically controlling > > > > the > > > > - * device's power. If we're using protocol specific settings, > > > > we don't > > > > - * want pci interfering. > > > > - */ > > > > - pci_save_state(pdev); > > > > unfreeze: > > > > nvme_unfreeze(ctrl); > > > > return ret; > > > > > > In the event that something else fails after the point you've saved > > > the state, we need to fallback to the behavior for when the driver > > > doesn't save the state, right? > > > > Depending on whether or not an error is going to be returned. > > > > When returning an error, it is not necessary to worry about the saved state, > > because that will cause the entire system-wide suspend to be aborted. > > It looks like in this case an error would be returned.
Not necessarily. If nvme_set_power_state() returns a positive number, you need to clear pdev->state_saved before jumping to unfreeze. Actually, you can drop the "goto unfreeze" after the "ret = 0" (in the "if (ret)" block) and add the clearing of pdev->state_saved before it. Let me reply to the original patch, though. > > > > > Otherwise it is sufficient to clear the state_saved flag of the PCI device > > before returning 0 to make the PCI layer take over. >
