On Tue, Jun 22, 2021 at 12:20 AM Dmitry Torokhov
<dmitry.torokhov@xxxxxxxxx> wrote:
>
> Currently ACPI power domain brings devices into D0 state in the "resume
> early" phase. Normally this does not cause any issues, as powering up
> happens quickly. However there are peripherals that have certain timing
> requirements for powering on, for example some models of Elan
> touchscreens need 300msec after powering up/releasing reset line before
> they can accept commands from the host. Such devices will dominate
> the time spent in early resume phase and cause increase in overall
> resume time as we wait for early resume to complete before we can
> proceed to the normal resume stage.
>
> There are ways for a driver to indicate that it can tolerate device
> being in the low power mode and that it knows how to power the device
> back up when resuming, bit that requires changes to individual drivers
> that may not really care about details of ACPI controlled power
> management.
>
> This change attempts to solve this issue at ACPI power domain level, by
> postponing powering up device until we get to the normal resume stage,
> unless there is early resume handler defined for the device, or device
> does not declare any resume handlers, in which case we continue powering
> up such devices early. This allows us to shave off several hundred
> milliseconds of resume time on affected systems.
>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> ---
> drivers/acpi/device_pm.c | 46 +++++++++++++++++++++++++++++++++++-----
> 1 file changed, 41 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
> index 096153761ebc..00b412ccb2e0 100644
> --- a/drivers/acpi/device_pm.c
> +++ b/drivers/acpi/device_pm.c
> @@ -1131,17 +1131,52 @@ static int acpi_subsys_resume_noirq(struct device *dev)
> *
> * Use ACPI to put the given device into the full-power state and carry out the
> * generic early resume procedure for it during system transition into the
> - * working state.
> + * working state, but only do that if device either defines early resume
> + * handler, or does not define power operations at all. Otherwise powering up
> + * of the device is postponed to the normal resume phase.
> */
> static int acpi_subsys_resume_early(struct device *dev)
> {
> + const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
> + struct acpi_device *adev = ACPI_COMPANION(dev);
> int ret;
>
> - if (dev_pm_skip_resume(dev))
> - return 0;
The above doesn't need to be changed AFAICS.
> + if (dev_pm_skip_resume(dev)) {
> + ret = 0;
> + } else if (!pm || pm->resume_early) {
This is rather tricky, but I don't see a particular reason why it wouldn't work.
> + ret = acpi_dev_resume(dev);
> + if (!ret)
> + ret = pm_generic_resume_early(dev);
> + } else {
> + if (adev)
> + acpi_device_wakeup_disable(adev);
This isn't necessary here.
> +
> + dev_dbg(dev, "postponing D0 transition to normal resume stage\n");
> + ret = 0;
> + }
> +
> + return ret;
> +}
> +
> +/**
> + * acpi_subsys_resume - Resume device using ACPI.
> + * @dev: Device to Resume.
> + *
> + * Use ACPI to put the given device into the full-power state if it has not been
> + * powered up during early resume phase, and carry out the generic resume
> + * procedure for it during system transition into the working state.
> + */
> +static int acpi_subsys_resume(struct device *dev)
> +{
> + const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
> + int ret = 0;
> +
> + if (!dev_pm_skip_resume(dev) && pm && !pm->resume_early) {
> + dev_dbg(dev, "executing postponed D0 transition\n");
> + ret = acpi_dev_resume(dev);
> + }
>
> - ret = acpi_dev_resume(dev);
> - return ret ? ret : pm_generic_resume_early(dev);
> + return ret ? ret : pm_generic_resume(dev);
> }
>
> /**
> @@ -1236,6 +1271,7 @@ static struct dev_pm_domain acpi_general_pm_domain = {
> .prepare = acpi_subsys_prepare,
> .complete = acpi_subsys_complete,
> .suspend = acpi_subsys_suspend,
> + .resume = acpi_subsys_resume,
> .suspend_late = acpi_subsys_suspend_late,
> .suspend_noirq = acpi_subsys_suspend_noirq,
> .resume_noirq = acpi_subsys_resume_noirq,
> --
