linux-kernel - Re: [PATCH v2 3/3] PM: domains: Power off[on] domain in hibernate .freeze[thaw]

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Date:   Tue, 1 Nov 2022 11:24:39 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Shawn Guo <shawn.guo@...aro.org>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] PM: domains: Power off[on] domain in hibernate
 .freeze[thaw]_noirq hook

On Tue, 1 Nov 2022 at 03:47, Shawn Guo <shawn.guo@...aro.org> wrote:
>
> On platforms which use SHUTDOWN as hibernation mode, the genpd noirq
> hooks will be called like below.
>
>     genpd_freeze_noirq()         genpd_restore_noirq()
>           ↓                            ↑
>     Create snapshot image        Restore system
>           ↓                            ↑
>     genpd_thaw_noirq()           Read snapshot image
>           ↓                            ↑
>     Write snapshot image         Kernel boot
>           ↓                            ↑
>     power_down()                 Power on device
>
> As of today suspend hooks genpd_suspend[resume]_noirq() manages domain
> on/off state, but hibernate hooks genpd_freeze[thaw]_noirq() doesn't.
> This results in a different behavior of domain power state between suspend
> and hibernate freeze, i.e. domain is powered off for the former while on
> for the later.  It causes a problem on platforms like i.MX where the
> domain needs to be powered on/off by calling clock and regulator interface.
> When the platform restores from hibernation, the domain is off in hardware
> and genpd_restore_noirq() tries to power it on, but will never succeed
> because software state of domain (clock and regulator) is left on from the
> last hibernate freeze, so kernel thinks that clock and regulator are
> enabled while they are actually not turned on in hardware.  The
> consequence would be that devices in the power domain will access
> registers without clock or power, and cause hardware lockup.
>
> Power off[on] domain in hibernate .freeze[thaw]_noirq hook for reasons:
>
> - Align the behavior between suspend and hibernate freeze.
> - Have power state of domains stay in sync between hardware and software
>   for hibernate freeze, and thus fix the lockup issue seen on i.MX
>   platform.
>
> Signed-off-by: Shawn Guo <shawn.guo@...aro.org>

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>  drivers/base/power/domain.c | 35 ++++-------------------------------
>  1 file changed, 4 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index b81baeb38d81..28c9e04e3488 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -1323,24 +1323,11 @@ static int genpd_resume_noirq(struct device *dev)
>   */
>  static int genpd_freeze_noirq(struct device *dev)
>  {
> -       const struct generic_pm_domain *genpd;
> -       int ret = 0;
> -
>         dev_dbg(dev, "%s()\n", __func__);
>
> -       genpd = dev_to_genpd(dev);
> -       if (IS_ERR(genpd))
> -               return -EINVAL;
> -
> -       ret = pm_generic_freeze_noirq(dev);
> -       if (ret)
> -               return ret;
> -
> -       if (genpd->dev_ops.stop && genpd->dev_ops.start &&
> -           !pm_runtime_status_suspended(dev))
> -               ret = genpd_stop_dev(genpd, dev);
> -
> -       return ret;
> +       return genpd_finish_suspend(dev,
> +                                   pm_generic_freeze_noirq,
> +                                   pm_generic_thaw_noirq);
>  }
>
>  /**
> @@ -1352,23 +1339,9 @@ static int genpd_freeze_noirq(struct device *dev)
>   */
>  static int genpd_thaw_noirq(struct device *dev)
>  {
> -       const struct generic_pm_domain *genpd;
> -       int ret = 0;
> -
>         dev_dbg(dev, "%s()\n", __func__);
>
> -       genpd = dev_to_genpd(dev);
> -       if (IS_ERR(genpd))
> -               return -EINVAL;
> -
> -       if (genpd->dev_ops.stop && genpd->dev_ops.start &&
> -           !pm_runtime_status_suspended(dev)) {
> -               ret = genpd_start_dev(genpd, dev);
> -               if (ret)
> -                       return ret;
> -       }
> -
> -       return pm_generic_thaw_noirq(dev);
> +       return genpd_finish_resume(dev, pm_generic_thaw_noirq);
>  }
>
>  /**
> --
> 2.25.1
>