On Fri, Dec 8, 2023 at 3:09 PM David Stevens <steve...@chromium.org> wrote:
>
> If a virtio_pci_device supports native PCI power management and has the
> No_Soft_Reset bit set, then skip resetting and reinitializing the device
> when suspending and restoring the device. This allows system-wide low
> power states like s2idle to be used in systems with stateful virtio
> devices that can't simply be re-initialized (e.g. virtio-fs).
>
> Signed-off-by: David Stevens <steve...@chromium.org>
Acked-by: Jason Wang <jasow...@redhat.com>
Thanks
> ---
> v1 -> v2:
> - Check the No_Soft_Reset bit
>
> drivers/virtio/virtio_pci_common.c | 34 +++++++++++++++++++++++++++++-
> 1 file changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_pci_common.c
> b/drivers/virtio/virtio_pci_common.c
> index c2524a7207cf..3a95ecaf12dc 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -492,8 +492,40 @@ static int virtio_pci_restore(struct device *dev)
> return virtio_device_restore(&vp_dev->vdev);
> }
>
> +static bool vp_supports_pm_no_reset(struct device *dev)
> +{
> + struct pci_dev *pci_dev = to_pci_dev(dev);
> + u16 pmcsr;
> +
> + if (!pci_dev->pm_cap)
> + return false;
> +
> + pci_read_config_word(pci_dev, pci_dev->pm_cap + PCI_PM_CTRL, &pmcsr);
> + if (PCI_POSSIBLE_ERROR(pmcsr)) {
> + dev_err(dev, "Unable to query pmcsr");
> + return false;
> + }
> +
> + return pmcsr & PCI_PM_CTRL_NO_SOFT_RESET;
> +}
> +
> +static int virtio_pci_suspend(struct device *dev)
> +{
> + return vp_supports_pm_no_reset(dev) ? 0 : virtio_pci_freeze(dev);
> +}
> +
> +static int virtio_pci_resume(struct device *dev)
> +{
> + return vp_supports_pm_no_reset(dev) ? 0 : virtio_pci_restore(dev);
> +}
> +
> static const struct dev_pm_ops virtio_pci_pm_ops = {
> - SET_SYSTEM_SLEEP_PM_OPS(virtio_pci_freeze, virtio_pci_restore)
> + .suspend = virtio_pci_suspend,
> + .resume = virtio_pci_resume,
> + .freeze = virtio_pci_freeze,
> + .thaw = virtio_pci_restore,
> + .poweroff = virtio_pci_freeze,
> + .restore = virtio_pci_restore,
> };
> #endif
>
> --
> 2.43.0.472.g3155946c3a-goog
>
