Re: [PATCH v2 1/2] cpuidle: psci: Move enabling OSI mode after power domains creation

[Ulf Hansson]

On Thu, 30 Mar 2023 at 10:43, Maulik Shah <quic_mkshah@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> ---
>  drivers/cpuidle/cpuidle-psci-domain.c | 29 +++++++--------------------
>  1 file changed, 7 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> index 11316c3b14ca..d81f6ae35002 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.
> @@ -178,13 +161,18 @@ 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;
>
>         /* Link genpd masters/subdomains to model the CPU topology. */
>         ret = dt_idle_pd_init_topology(np);
>         if (ret)
>                 goto remove_pd;
>
> +       /* let's try to enable OSI. */
> +       ret = psci_set_osi_mode(use_osi);
> +       if (ret)
> +               goto remove_pd;

If this fails, subdomains that were added in
dt_idle_pd_init_topology() should be removed too. In other words, we
need a add a new helper function in drivers/cpuidle/dt_idle_genpd.c,
that we can call before calling psci_pd_remove() for this error path.

> +
>         pr_info("Initialized CPU PM domain topology using %s mode\n",
>                 use_osi ? "OSI" : "PC");
>         return 0;
> @@ -194,9 +182,6 @@ static int psci_cpuidle_domain_probe(struct platform_device *pdev)
>  remove_pd:
>         psci_pd_remove();
>         pr_err("failed to create CPU PM domains ret=%d\n", ret);
> -no_pd:
> -       if (use_osi)
> -               psci_set_osi_mode(false);
>         return ret;
>  }
>

Other than the above, this looks good to me.

Kind regards
Uffe