linux-kernel - Re: [PATCH v10 21/27] drivers: firmware: psci: Add a helper to attach a CPU to its PM domain

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Message-ID: <CAPDyKFqv+1R-hbSmgfrn8jtBXEB3S1-=bg+ArBkR4m-cxd2oQQ@mail.gmail.com>
Date:   Thu, 6 Dec 2018 10:15:23 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Lina Iyer <ilina@...eaurora.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Raju P.L.S.S.S.N" <rplsssn@...eaurora.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Kevin Hilman <khilman@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 21/27] drivers: firmware: psci: Add a helper to attach
 a CPU to its PM domain

On Tue, 4 Dec 2018 at 19:45, Lina Iyer <ilina@...eaurora.org> wrote:
>
> On Thu, Nov 29 2018 at 10:50 -0700, Ulf Hansson wrote:
> >Introduce a new PSCI DT helper function, psci_dt_attach_cpu(), which takes
> >a CPU number as an in-parameter and attaches the CPU's struct device to its
> >corresponding PM domain. Additionally, the helper prepares the CPU to be
> >power managed via runtime PM, which is the last step needed to enable the
> >interaction with the PM domain through the runtime PM callbacks.
> >
> >Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> >---
> >
> >Changes in v10:
> >       - New patch: Replaces "PM / Domains: Add helper functions to
> >         attach/detach CPUs to/from genpd".
> >
> >---
> > drivers/firmware/psci/psci.h           |  1 +
> > drivers/firmware/psci/psci_pm_domain.c | 19 +++++++++++++++++++
> > 2 files changed, 20 insertions(+)
> >
> >diff --git a/drivers/firmware/psci/psci.h b/drivers/firmware/psci/psci.h
> >index 05af462cc96e..fbc9980dee69 100644
> >--- a/drivers/firmware/psci/psci.h
> >+++ b/drivers/firmware/psci/psci.h
> >@@ -15,6 +15,7 @@ int psci_dt_parse_state_node(struct device_node *np, u32 *state);
> > int psci_dt_init_pm_domains(struct device_node *np);
> > int psci_dt_pm_domains_parse_states(struct cpuidle_driver *drv,
> >                       struct device_node *cpu_node, u32 *psci_states);
> >+int psci_dt_attach_cpu(int cpu);
> > #else
> > static inline int psci_dt_init_pm_domains(struct device_node *np) { return 0; }
> > #endif
> >diff --git a/drivers/firmware/psci/psci_pm_domain.c b/drivers/firmware/psci/psci_pm_domain.c
> >index 6c9d6a644c7f..b0fa7da8a0ce 100644
> >--- a/drivers/firmware/psci/psci_pm_domain.c
> >+++ b/drivers/firmware/psci/psci_pm_domain.c
> >@@ -12,8 +12,10 @@
> > #include <linux/device.h>
> > #include <linux/kernel.h>
> > #include <linux/pm_domain.h>
> >+#include <linux/pm_runtime.h>
> > #include <linux/slab.h>
> > #include <linux/string.h>
> >+#include <linux/cpu.h>
> > #include <linux/cpuidle.h>
> > #include <linux/cpu_pm.h>
> >
> >@@ -367,4 +369,21 @@ int psci_dt_pm_domains_parse_states(struct cpuidle_driver *drv,
> >
> >       return 0;
> > }
> >+
> >+int psci_dt_attach_cpu(int cpu)
> >+{
> >+      struct device *dev = get_cpu_device(cpu);
> >+      int ret;
> >+
> >+      ret = dev_pm_domain_attach(dev, true);
> >+      if (ret)
> >+              return ret;
> >+
> >+      pm_runtime_irq_safe(dev);
> >+      pm_runtime_get_noresume(dev);
> >+      pm_runtime_set_active(dev);
> You would want to set this only if the CPU is online. Otherwise we will
> not power down the domain, if the CPU was never brought online.

Nice catch!

The platforms I tested this series on brings all their CPUs online
during boot, hence I haven't observed the problem.

I will post a new version soon to address the problem. Again, thanks
for your review!

[...]

Kind regards
Uffe