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    SubjectRe: [PATCH] nvme-pci: Save PCI state before putting drive into deepest state
    Date
    On Thursday, September 12, 2019 1:42:33 AM CEST 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.

    This sounds reasonable to me, but it would be nice to CC that to linux-pm
    and/or linux-pci too.

    > Signed-off-by: Mario Limonciello <mario.limonciello@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)

    This is the case in which the PCI layer is expected to put the device into
    D3, so you need

    pdev->state_saved = 0;

    at this point, because you have saved the config space already.

    > ret = 0;
    > goto unfreeze;

    And here you don't need to jump to "unfreeze" any more.

    > }
    > - /*
    > - * 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;
    >




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