linux-kernel - Re: [PATCH v3 2/3] cpuidle: psci: Move enabling OSI mode after power domains creation

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Date:   Tue, 18 Apr 2023 10:12:30 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Maulik Shah <quic_mkshah@...cinc.com>
Cc:     andersson@...nel.org, dianders@...omium.org, swboyd@...omium.org,
        wingers@...gle.com, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        sudeep.holla@....com, jwerner@...omium.org, quic_lsrao@...cinc.com,
        quic_rjendra@...cinc.com
Subject: Re: [PATCH v3 2/3] cpuidle: psci: Move enabling OSI mode after power
 domains creation

On Fri, 14 Apr 2023 at 07:55, Maulik Shah <quic_mkshah@...cinc.com> wrote:
>
> A switch from OSI to PC mode is only possible if all CPUs other than the
> calling one are OFF, either through a call to CPU_OFF or not yet booted.
>
> Currently OSI mode is enabled before power domains are created. In cases
> where CPUidle states are not using hierarchical CPU topology the bail out
> path tries to switch back to PC mode which gets denied by firmware since
> other CPUs are online at this point and creates inconsistent state as
> firmware is in OSI mode and Linux in PC mode.
>
> This change moves enabling OSI mode after power domains are created,
> this would makes sure that hierarchical CPU topology is used before
> switching firmware to OSI mode.
>
> Fixes: 70c179b49870 ("cpuidle: psci: Allow PM domain to be initialized even if no OSI mode")
> Signed-off-by: Maulik Shah <quic_mkshah@...cinc.com>
> ---
>  drivers/cpuidle/cpuidle-psci-domain.c | 37 +++++++++------------------
>  1 file changed, 12 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> index c2d6d9c3c930..c3993df24eef 100644
> --- a/drivers/cpuidle/cpuidle-psci-domain.c
> +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> @@ -120,20 +120,6 @@ static void psci_pd_remove(void)
>         }
>  }
>
> -static bool psci_pd_try_set_osi_mode(void)
> -{
> -       int ret;
> -
> -       if (!psci_has_osi_support())
> -               return false;
> -
> -       ret = psci_set_osi_mode(true);
> -       if (ret)
> -               return false;
> -
> -       return true;
> -}
> -
>  static void psci_cpuidle_domain_sync_state(struct device *dev)
>  {
>         /*
> @@ -152,15 +138,12 @@ static int psci_cpuidle_domain_probe(struct platform_device *pdev)
>  {
>         struct device_node *np = pdev->dev.of_node;
>         struct device_node *node;
> -       bool use_osi;
> +       bool use_osi = psci_has_osi_support();
>         int ret = 0, pd_count = 0;
>
>         if (!np)
>                 return -ENODEV;
>
> -       /* If OSI mode is supported, let's try to enable it. */
> -       use_osi = psci_pd_try_set_osi_mode();
> -
>         /*
>          * Parse child nodes for the "#power-domain-cells" property and
>          * initialize a genpd/genpd-of-provider pair when it's found.
> @@ -178,25 +161,29 @@ static int psci_cpuidle_domain_probe(struct platform_device *pdev)
>
>         /* Bail out if not using the hierarchical CPU topology. */
>         if (!pd_count)
> -               goto no_pd;
> +               goto remove_pd;

We should return 0 here instead, right?

>
>         /* Link genpd masters/subdomains to model the CPU topology. */
>         ret = dt_idle_pd_init_topology(np);
>         if (ret)
> -               goto remove_pd;
> +               goto remove_pd_topology;

This looks wrong to me. Shouldn't we continue to goto the "remove_pd"
label for this error path?

> +
> +       /* let's try to enable OSI. */
> +       ret = psci_set_osi_mode(use_osi);
> +       if (ret)
> +               goto remove_pd_topology;
>
>         pr_info("Initialized CPU PM domain topology using %s mode\n",
>                 use_osi ? "OSI" : "PC");
>         return 0;
>
> -put_node:
> -       of_node_put(node);
> +remove_pd_topology:
> +       dt_idle_pd_remove_topology(np);
>  remove_pd:
>         psci_pd_remove();
> +put_node:
> +       of_node_put(node);

This of_node_put() should only be called if we break the
"for_each_child_of_node" loop above because of an error, I think.
Perhaps it's cleaner to just move this within the loop?

>         pr_err("failed to create CPU PM domains ret=%d\n", ret);
> -no_pd:
> -       if (use_osi)
> -               psci_set_osi_mode(false);
>         return ret;
>  }
>

Kind regards
Uffe