linux-kernel - Re: [PATCH v5 2/3] power: domain: handle genpd correctly when needing interrupts

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Message-ID: <CAPDyKFouWMVcbDyrs=KgC+R4E61nb45Y0yOjt3PZ3JfcRyY9dA@mail.gmail.com>
Date:   Thu, 21 Jul 2022 13:16:47 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Martin Kepplinger <martin.kepplinger@...i.sm>
Cc:     rafael@...nel.org, khilman@...nel.org, robh@...nel.org,
        krzysztof.kozlowski@...aro.org, shawnguo@...nel.org,
        s.hauer@...gutronix.de, festevam@...il.com, pavel@....cz,
        kernel@...i.sm, linux-imx@....com, broonie@...nel.org,
        l.stach@...gutronix.de, aford173@...il.com,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v5 2/3] power: domain: handle genpd correctly when needing interrupts

On Thu, 21 Jul 2022 at 06:37, Martin Kepplinger
<martin.kepplinger@...i.sm> wrote:
>
> If for example the power-domains' power-supply node (regulator) needs
> interrupts to work, the current setup with noirq callbacks cannot
> work; for example a pmic regulator on i2c, when suspending, usually already
> times out during suspend_noirq:
>
> [   41.024193] buck4: failed to disable: -ETIMEDOUT
>
> So fix system suspend and resume for these power-domains by using the
> "outer" suspend/resume callbacks instead. Tested on the imx8mq-librem5 board,
> but by looking at the dts, this will fix imx8mq-evk and possibly many other
> boards too.
>
> This is designed so that genpd providers just say "this genpd needs
> interrupts" (by setting the flag) - without implying an implementation.
>
> Initially system suspend problems had been discussed at
> https://lore.kernel.org/linux-arm-kernel/20211002005954.1367653-8-l.stach@pengutronix.de/
> which led to discussing the pmic that contains the regulators which
> serve as power-domain power-supplies:
> https://lore.kernel.org/linux-pm/573166b75e524517782471c2b7f96e03fd93d175.camel@puri.sm/T/
>
> Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
> ---
>  drivers/base/power/domain.c | 13 +++++++++++++
>  include/linux/pm_domain.h   |  5 +++++
>  2 files changed, 18 insertions(+)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 5a2e0232862e..ef77700e0def 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -130,6 +130,7 @@ static const struct genpd_lock_ops genpd_spin_ops = {
>  #define genpd_is_active_wakeup(genpd)  (genpd->flags & GENPD_FLAG_ACTIVE_WAKEUP)
>  #define genpd_is_cpu_domain(genpd)     (genpd->flags & GENPD_FLAG_CPU_DOMAIN)
>  #define genpd_is_rpm_always_on(genpd)  (genpd->flags & GENPD_FLAG_RPM_ALWAYS_ON)
> +#define genpd_irq_on(genpd)            (genpd->flags & GENPD_FLAG_IRQ_ON)
>
>  static inline bool irq_safe_dev_in_sleep_domain(struct device *dev,
>                 const struct generic_pm_domain *genpd)
> @@ -2079,6 +2080,13 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
>                 genpd->dev_ops.start = pm_clk_resume;
>         }
>
> +       if (genpd_irq_on(genpd)) {
> +               genpd->domain.ops.suspend = genpd_suspend_noirq;
> +               genpd->domain.ops.resume = genpd_resume_noirq;
> +               genpd->domain.ops.suspend_noirq = NULL;
> +               genpd->domain.ops.resume_noirq = NULL;

Please move this a few lines above, just before we assign the _*noirq
callbacks. In this way you don't need to reset thosepointers.

> +       }
> +
>         /* The always-on governor works better with the corresponding flag. */
>         if (gov == &pm_domain_always_on_gov)
>                 genpd->flags |= GENPD_FLAG_RPM_ALWAYS_ON;
> @@ -2769,6 +2777,11 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
>                         goto err;
>                 dev_gpd_data(dev)->default_pstate = pstate;
>         }
> +
> +       if (pd->domain.ops.suspend_noirq && (pd->flags & GENPD_FLAG_IRQ_ON))
> +               dev_err(dev, "PM domain %s needs irqs but uses noirq suspend\n",
> +                       pd->name);
> +

This doesn't make sense, as it can never happen according to what we
do in pm_genpd_init().

What Lucas suggested in the other thread was to log a warning if a
device's (that gets attached to genpd) bus/driver has _*noirq
callbacks. That would make sense.

Thinking more about this, perhaps we should move to use the
_*late/early callbacks instead for genpd. This would decrease the
window of potential problematic consumers users (drivers/buses).

>         return 1;
>
>  err:
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 76bc9e3ef5ff..03bb86e43550 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -61,6 +61,10 @@
>   * GENPD_FLAG_MIN_RESIDENCY:   Enable the genpd governor to consider its
>   *                             components' next wakeup when determining the
>   *                             optimal idle state.
> + *
> + * GENPD_FLAG_IRQ_ON:          genpd needs irqs to be able to manage power
> + *                             on/off. Use the outer suspend/resume callbacks
> + *                             instead of noirq for example.
>   */
>  #define GENPD_FLAG_PM_CLK              BIT(0)
>  #define GENPD_FLAG_IRQ_SAFE            BIT(1)
> @@ -69,6 +73,7 @@
>  #define GENPD_FLAG_CPU_DOMAIN          BIT(4)
>  #define GENPD_FLAG_RPM_ALWAYS_ON       BIT(5)
>  #define GENPD_FLAG_MIN_RESIDENCY       BIT(6)
> +#define GENPD_FLAG_IRQ_ON              BIT(7)
>
>  enum gpd_status {
>         GENPD_STATE_ON = 0,     /* PM domain is on */
> --
> 2.30.2
>

Kind regards
Uffe