[v10,24/27] drivers: firmware: psci: Support CPU hotplug for the hierarchical model

Message ID 20181129174700.16585-25-ulf.hansson@linaro.org
State New
Headers show
Series
  • PM / Domains: Support hierarchical CPU arrangement (PSCI/ARM)
Related show

Commit Message

Ulf Hansson Nov. 29, 2018, 5:46 p.m.
When the hierarchical CPU topology is used and when a CPU has been put
offline (hotplug), that same CPU prevents its PM domain and thus also
potential master PM domains, from being powered off. This is because genpd
observes the CPU's struct device to remain being active from a runtime PM
point of view.

To deal with this, let's decrease the runtime PM usage count by calling
pm_runtime_put_sync_suspend() of the CPU's struct device when putting it
offline. Consequentially, we must then increase the runtime PM usage for
the CPU, while putting it online again.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

---

Changes in v10:
	- Make it work when the hierarchical CPU topology is used, which may be
	  used both for OSI and PC mode.
	- Rework the code to prevent "BUG: sleeping function called from
	  invalid context".
---
 drivers/firmware/psci/psci.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

-- 
2.17.1

Comments

Lorenzo Pieralisi Dec. 19, 2018, 11:17 a.m. | #1
On Thu, Nov 29, 2018 at 06:46:57PM +0100, Ulf Hansson wrote:
> When the hierarchical CPU topology is used and when a CPU has been put

> offline (hotplug), that same CPU prevents its PM domain and thus also

> potential master PM domains, from being powered off. This is because genpd

> observes the CPU's struct device to remain being active from a runtime PM

> point of view.

> 

> To deal with this, let's decrease the runtime PM usage count by calling

> pm_runtime_put_sync_suspend() of the CPU's struct device when putting it

> offline. Consequentially, we must then increase the runtime PM usage for

> the CPU, while putting it online again.

> 

> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

> ---

> 

> Changes in v10:

> 	- Make it work when the hierarchical CPU topology is used, which may be

> 	  used both for OSI and PC mode.

> 	- Rework the code to prevent "BUG: sleeping function called from

> 	  invalid context".

> ---

>  drivers/firmware/psci/psci.c | 20 ++++++++++++++++++++

>  1 file changed, 20 insertions(+)

> 

> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c

> index b03bccce0a5d..f62c4963eb62 100644

> --- a/drivers/firmware/psci/psci.c

> +++ b/drivers/firmware/psci/psci.c

> @@ -15,6 +15,7 @@

>  

>  #include <linux/acpi.h>

>  #include <linux/arm-smccc.h>

> +#include <linux/cpu.h>

>  #include <linux/cpuidle.h>

>  #include <linux/errno.h>

>  #include <linux/linkage.h>

> @@ -199,9 +200,20 @@ static int psci_cpu_suspend(u32 state, unsigned long entry_point)

>  

>  static int psci_cpu_off(u32 state)

>  {

> +	struct device *dev;

>  	int err;

>  	u32 fn;

>  

> +	/*

> +	 * When the hierarchical CPU topology is used, decrease the runtime PM

> +	 * usage count for the current CPU, as to allow other parts in the

> +	 * topology to enter low power states.

> +	 */

> +	if (psci_dt_topology) {

> +		dev = get_cpu_device(smp_processor_id());

> +		pm_runtime_put_sync_suspend(dev);

> +	}

> +

>  	fn = psci_function_id[PSCI_FN_CPU_OFF];

>  	err = invoke_psci_fn(fn, state, 0, 0);

>  	return psci_to_linux_errno(err);

> @@ -209,6 +221,7 @@ static int psci_cpu_off(u32 state)

>  

>  static int psci_cpu_on(unsigned long cpuid, unsigned long entry_point)

>  {

> +	struct device *dev;

>  	int err;

>  	u32 fn;

>  

> @@ -216,6 +229,13 @@ static int psci_cpu_on(unsigned long cpuid, unsigned long entry_point)

>  	err = invoke_psci_fn(fn, cpuid, entry_point, 0);

>  	/* Clear the domain state to start fresh. */

>  	psci_set_domain_state(0);

> +

> +	/* Increase runtime PM usage count if the hierarchical CPU toplogy. */

> +	if (!err && psci_dt_topology) {

> +		dev = get_cpu_device(cpuid);


I do not like adding this code in the cpu_{on/off} method themselves, I will
have a look at the patchset as whole to see how we can restructure it.

More to the point, using cpuid as a logical cpu id is wrong, it is a
physical id that you should convert to a logical id through
get_logical_index().

Lorenzo

> +		pm_runtime_get_sync(dev);

> +	}

> +

>  	return psci_to_linux_errno(err);

>  }

>  

> -- 

> 2.17.1

>

Patch

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index b03bccce0a5d..f62c4963eb62 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -15,6 +15,7 @@ 
 
 #include <linux/acpi.h>
 #include <linux/arm-smccc.h>
+#include <linux/cpu.h>
 #include <linux/cpuidle.h>
 #include <linux/errno.h>
 #include <linux/linkage.h>
@@ -199,9 +200,20 @@  static int psci_cpu_suspend(u32 state, unsigned long entry_point)
 
 static int psci_cpu_off(u32 state)
 {
+	struct device *dev;
 	int err;
 	u32 fn;
 
+	/*
+	 * When the hierarchical CPU topology is used, decrease the runtime PM
+	 * usage count for the current CPU, as to allow other parts in the
+	 * topology to enter low power states.
+	 */
+	if (psci_dt_topology) {
+		dev = get_cpu_device(smp_processor_id());
+		pm_runtime_put_sync_suspend(dev);
+	}
+
 	fn = psci_function_id[PSCI_FN_CPU_OFF];
 	err = invoke_psci_fn(fn, state, 0, 0);
 	return psci_to_linux_errno(err);
@@ -209,6 +221,7 @@  static int psci_cpu_off(u32 state)
 
 static int psci_cpu_on(unsigned long cpuid, unsigned long entry_point)
 {
+	struct device *dev;
 	int err;
 	u32 fn;
 
@@ -216,6 +229,13 @@  static int psci_cpu_on(unsigned long cpuid, unsigned long entry_point)
 	err = invoke_psci_fn(fn, cpuid, entry_point, 0);
 	/* Clear the domain state to start fresh. */
 	psci_set_domain_state(0);
+
+	/* Increase runtime PM usage count if the hierarchical CPU toplogy. */
+	if (!err && psci_dt_topology) {
+		dev = get_cpu_device(cpuid);
+		pm_runtime_get_sync(dev);
+	}
+
 	return psci_to_linux_errno(err);
 }