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: <20181204184553.GO18262@codeaurora.org>
Date:   Tue, 4 Dec 2018 11:45:53 -0700
From:   Lina Iyer <ilina@...eaurora.org>
To:     Ulf Hansson <ulf.hansson@...aro.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@...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-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, 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 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.
>+	pm_runtime_enable(dev);
>+
>+	return 0;
>+}
> #endif
>-- 
>2.17.1
>