linux-kernel - Re: [PATCH v4 1/2] PM / Domains: Add support for 'required-opps' to set default perf state

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Date:   Fri, 16 Jul 2021 22:19:46 +0200
From:   Stephen Boyd <swboyd@...omium.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>, bjorn.andersson@...aro.org,
        ulf.hansson@...aro.org, viresh.kumar@...aro.org
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        rojay@...eaurora.org, stephan@...hold.net
Subject: Re: [PATCH v4 1/2] PM / Domains: Add support for 'required-opps' to
 set default perf state

Quoting Rajendra Nayak (2021-07-16 03:00:57)
> Some devics within power domains with performance states do not

devices

> support DVFS, but still need to vote on a default/static state
> while they are active. They can express this using the 'required-opps'
> property in device tree, which points to the phandle of the OPP
> supported by the corresponding power-domains.
>
> Add support to parse this information from DT and then set the
> specified performance state during attach and drop it on detach.
> Also drop/set as part of runtime suspend/resume callbacks.
>
> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> ---
>  drivers/base/power/domain.c | 37 ++++++++++++++++++++++++++++++++++---
>  include/linux/pm_domain.h   |  1 +
>  2 files changed, 35 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index a934c67..dcc0b71 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -1000,6 +1008,8 @@ static int genpd_runtime_resume(struct device *dev)
>         genpd_stop_dev(genpd, dev);
>  err_poweroff:
>         if (!pm_runtime_is_irq_safe(dev) || genpd_is_irq_safe(genpd)) {
> +               if (default_pstate)
> +                       dev_pm_genpd_set_performance_state(dev, 0);
>                 genpd_lock(genpd);
>                 gpd_data->rpm_pstate = genpd_drop_performance_state(dev);

Maybe this should be

		  prev_state = genpd_drop_performance_state(dev);
		  if (!default_pstate)
		  	gdp_data->rpm_pstate = prev_state;

so we don't call dev_pm_genpd_set_performance_state() effectively twice?
Also it would make sure we call dev_pm_genpd_set_performance_state()
underneath the genpd_lock() if that is important. Similarly do that on
suspend path.

>                 genpd_power_off(genpd, true, 0);
> @@ -2598,6 +2608,12 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
>
>         dev_dbg(dev, "removing from PM domain %s\n", pd->name);
>
> +       /* Drop the default performance state */
> +       if (dev_gpd_data(dev)->default_pstate) {
> +               dev_pm_genpd_set_performance_state(dev, 0);
> +               dev_gpd_data(dev)->default_pstate = 0;
> +       }
> +
>         for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {
>                 ret = genpd_remove_device(pd, dev);
>                 if (ret != -EAGAIN)
> @@ -2675,10 +2692,24 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
>                 genpd_unlock(pd);
>         }
>
> -       if (ret)
> +       if (ret) {
>                 genpd_remove_device(pd, dev);
> +               return -EPROBE_DEFER;
> +       }
> +
> +       /* Set the default performance state */
> +       np = base_dev->of_node;
> +       if (of_parse_phandle(np, "required-opps", index)) {
> +               pstate = of_get_required_opp_performance_state(np, index);
> +               if (pstate < 0) {
> +                       dev_err(dev, "failed to set pstate:%d", pstate);

Missing newline on printk. Also can we spell out pstate as "failed to
set required performance state %d for power-domain %d"?

> +                       ret = pstate;
> +               }
> +               dev_pm_genpd_set_performance_state(dev, pstate);
> +               dev_gpd_data(dev)->default_pstate = pstate;
> +       }
>
> -       return ret ? -EPROBE_DEFER : 1;
> +       return ret ? ret : 1;
>  }
>
>  /**