[PATCH v2 0/2] Add CPU power management for CPU bound CTI devices.

[PATCH v2 0/2] Add CPU power management for CPU bound CTI devices.

[Mike Leach]

Adds in power management for CPU bound CTI devices:
i) CPU Hotplug - registers a new notifier for CPU start and stop events.
ii) CPU idle PM event notifier to handle PM_ENTER, PM_ENTER_FAILED and
PM_EXIT events.

Tested with DB410c on Linux 5.7-rc3.
Rebased onto coresight/next

Changes since V1: (requested by Mathieu).
1) Split into separate patches for CPU pm and CPU hotplug handling.
2) Enable on hotplug has a specific function to enable the hardware,
while leaving the enable reference counts unchanged.

Mike Leach (2):
  coresight: cti: Add CPU Hotplug handling to CTI driver.
  coresight: cti: Add CPU idle pm notifer to CTI devices.

 drivers/hwtracing/coresight/coresight-cti.c | 173 ++++++++++++++++++++
 include/linux/cpuhotplug.h                  |   1 +
 2 files changed, 174 insertions(+)

-- 
2.17.1


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[PATCH v2 1/2] coresight: cti: Add CPU Hotplug handling to CTI driver.

[Mike Leach]

Adds registration of CPU start and stop functions to CPU hotplug
mechanisms - for any CPU bound CTI.

Sets CTI powered flag according to state.
Will enable CTI on CPU start if there are existing enable requests.

Signed-off-by: Mike Leach <mike.leach@linaro.org>
---
 drivers/hwtracing/coresight/coresight-cti.c | 91 +++++++++++++++++++++
 include/linux/cpuhotplug.h                  |  1 +
 2 files changed, 92 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
index be61c1705916..9af66719ae5b 100644
--- a/drivers/hwtracing/coresight/coresight-cti.c
+++ b/drivers/hwtracing/coresight/coresight-cti.c
@@ -40,6 +40,12 @@ static DEFINE_MUTEX(ect_mutex);
 #define csdev_to_cti_drvdata(csdev)	\
 	dev_get_drvdata(csdev->dev.parent)
 
+/* power management handling */
+static int nr_cti_cpu;
+
+/* quick lookup list for CPU bound CTIs when power handling */
+static struct cti_drvdata *cti_cpu_drvdata[NR_CPUS];
+
 /*
  * CTI naming. CTI bound to cores will have the name cti_cpu<N> where
  * N is the CPU ID. System CTIs will have the name cti_sys<I> where I
@@ -129,6 +135,35 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
 	return rc;
 }
 
+/* re-enable CTI on CPU when using CPU hotplug */
+static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata)
+{
+	struct cti_config *config = &drvdata->config;
+	struct device *dev = &drvdata->csdev->dev;
+
+	pm_runtime_get_sync(dev->parent);
+	spin_lock(&drvdata->spinlock);
+	config->hw_powered = true;
+
+	/* no need to do anything if no enable request */
+	if (!atomic_read(&drvdata->config.enable_req_count))
+		goto cti_hp_not_enabled;
+
+	/* try to claim the device */
+	if (coresight_claim_device(drvdata->base))
+		goto cti_hp_not_enabled;
+
+	cti_write_all_hw_regs(drvdata);
+	config->hw_enabled = true;
+	spin_unlock(&drvdata->spinlock);
+	return;
+
+	/* did not re-enable due to no claim / no request */
+cti_hp_not_enabled:
+	spin_unlock(&drvdata->spinlock);
+	pm_runtime_put(dev->parent);
+}
+
 /* disable hardware */
 static int cti_disable_hw(struct cti_drvdata *drvdata)
 {
@@ -620,6 +655,44 @@ static void cti_remove_conn_xrefs(struct cti_drvdata *drvdata)
 	}
 }
 
+/* CPU HP handlers */
+static int cti_starting_cpu(unsigned int cpu)
+{
+	struct cti_drvdata *drvdata = cti_cpu_drvdata[cpu];
+
+	if (!drvdata)
+		return 0;
+
+	cti_cpuhp_enable_hw(drvdata);
+	return 0;
+}
+
+static int cti_dying_cpu(unsigned int cpu)
+{
+	struct cti_drvdata *drvdata = cti_cpu_drvdata[cpu];
+
+	if (!drvdata)
+		return 0;
+
+	spin_lock(&drvdata->spinlock);
+	drvdata->config.hw_powered = false;
+	coresight_disclaim_device(drvdata->base);
+	spin_unlock(&drvdata->spinlock);
+	return 0;
+}
+
+/* release PM registrations */
+static void cti_pm_release(struct cti_drvdata *drvdata)
+{
+	if (drvdata->ctidev.cpu >= 0) {
+		if (--nr_cti_cpu == 0) {
+			cpuhp_remove_state_nocalls(
+				CPUHP_AP_ARM_CORESIGHT_CTI_STARTING);
+		}
+		cti_cpu_drvdata[drvdata->ctidev.cpu] = NULL;
+	}
+}
+
 /** cti ect operations **/
 int cti_enable(struct coresight_device *csdev)
 {
@@ -655,6 +728,7 @@ static void cti_device_release(struct device *dev)
 
 	mutex_lock(&ect_mutex);
 	cti_remove_conn_xrefs(drvdata);
+	cti_pm_release(drvdata);
 
 	/* remove from the list */
 	list_for_each_entry_safe(ect_item, ect_tmp, &ect_net, node) {
@@ -730,6 +804,22 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
 		goto err_out;
 	}
 
+	/* setup CPU power management handling for CPU bound CTI devices. */
+	if (drvdata->ctidev.cpu >= 0) {
+		cti_cpu_drvdata[drvdata->ctidev.cpu] = drvdata;
+		if (!nr_cti_cpu++) {
+			cpus_read_lock();
+			cpuhp_setup_state_nocalls_cpuslocked(
+				CPUHP_AP_ARM_CORESIGHT_CTI_STARTING,
+				"arm/coresight_cti:starting",
+				cti_starting_cpu, cti_dying_cpu);
+
+			cpus_read_unlock();
+			if (ret)
+				goto err_out;
+		}
+	}
+
 	/* create dynamic attributes for connections */
 	ret = cti_create_cons_sysfs(dev, drvdata);
 	if (ret) {
@@ -768,6 +858,7 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
 	return 0;
 
 err_out:
+	cti_pm_release(drvdata);
 	return ret;
 }
 
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 77d70b633531..6dc7332307ca 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -142,6 +142,7 @@ enum cpuhp_state {
 	CPUHP_AP_ARM_XEN_STARTING,
 	CPUHP_AP_ARM_KVMPV_STARTING,
 	CPUHP_AP_ARM_CORESIGHT_STARTING,
+	CPUHP_AP_ARM_CORESIGHT_CTI_STARTING,
 	CPUHP_AP_ARM64_ISNDEP_STARTING,
 	CPUHP_AP_SMPCFD_DYING,
 	CPUHP_AP_X86_TBOOT_DYING,
-- 
2.17.1


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[PATCH v2 2/2] coresight: cti: Add CPU idle pm notifer to CTI devices.

[Mike Leach]

Adds a notify callback for CPU PM events to the CTI driver - for
CPU bound CTI devices.

Signed-off-by: Mike Leach <mike.leach@linaro.org>
---
 drivers/hwtracing/coresight/coresight-cti.c | 82 +++++++++++++++++++++
 1 file changed, 82 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
index 9af66719ae5b..0f0c14528701 100644
--- a/drivers/hwtracing/coresight/coresight-cti.c
+++ b/drivers/hwtracing/coresight/coresight-cti.c
@@ -8,6 +8,7 @@
 #include <linux/atomic.h>
 #include <linux/bits.h>
 #include <linux/coresight.h>
+#include <linux/cpu_pm.h>
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -655,6 +656,84 @@ static void cti_remove_conn_xrefs(struct cti_drvdata *drvdata)
 	}
 }
 
+/** cti PM callbacks **/
+static int cti_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd,
+			     void *v)
+{
+	struct cti_drvdata *drvdata;
+	unsigned int cpu = smp_processor_id();
+	int notify_res = NOTIFY_OK;
+
+	if (!cti_cpu_drvdata[cpu])
+		return NOTIFY_OK;
+
+	drvdata = cti_cpu_drvdata[cpu];
+
+	if (WARN_ON_ONCE(drvdata->ctidev.cpu != cpu))
+		return NOTIFY_BAD;
+
+	spin_lock(&drvdata->spinlock);
+
+	switch (cmd) {
+	case CPU_PM_ENTER:
+		/* CTI regs all static - we have a copy & nothing to save */
+		drvdata->config.hw_powered = false;
+		if (drvdata->config.hw_enabled)
+			coresight_disclaim_device(drvdata->base);
+		break;
+
+	case CPU_PM_ENTER_FAILED:
+		drvdata->config.hw_powered = true;
+		if (drvdata->config.hw_enabled) {
+			if (coresight_claim_device(drvdata->base))
+				drvdata->config.hw_enabled = false;
+		}
+		break;
+
+	case CPU_PM_EXIT:
+		/* write hardware registers to re-enable. */
+		drvdata->config.hw_powered = true;
+		drvdata->config.hw_enabled = false;
+
+		/* check enable reference count to enable HW */
+		if (atomic_read(&drvdata->config.enable_req_count)) {
+			/* check we can claim the device as we re-power */
+			if (coresight_claim_device(drvdata->base))
+				goto cti_notify_exit;
+
+			drvdata->config.hw_enabled = true;
+			cti_write_all_hw_regs(drvdata);
+		}
+		break;
+
+	default:
+		notify_res = NOTIFY_DONE;
+		break;
+	}
+
+cti_notify_exit:
+	spin_unlock(&drvdata->spinlock);
+	return notify_res;
+}
+
+static struct notifier_block cti_cpu_pm_nb = {
+	.notifier_call = cti_cpu_pm_notify,
+};
+
+static int cti_cpu_pm_register(void)
+{
+	if (IS_ENABLED(CONFIG_CPU_PM))
+		return cpu_pm_register_notifier(&cti_cpu_pm_nb);
+
+	return 0;
+}
+
+static void cti_cpu_pm_unregister(void)
+{
+	if (IS_ENABLED(CONFIG_CPU_PM))
+		cpu_pm_unregister_notifier(&cti_cpu_pm_nb);
+}
+
 /* CPU HP handlers */
 static int cti_starting_cpu(unsigned int cpu)
 {
@@ -686,6 +765,8 @@ static void cti_pm_release(struct cti_drvdata *drvdata)
 {
 	if (drvdata->ctidev.cpu >= 0) {
 		if (--nr_cti_cpu == 0) {
+			cti_cpu_pm_unregister();
+
 			cpuhp_remove_state_nocalls(
 				CPUHP_AP_ARM_CORESIGHT_CTI_STARTING);
 		}
@@ -814,6 +895,7 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
 				"arm/coresight_cti:starting",
 				cti_starting_cpu, cti_dying_cpu);
 
+			ret = cti_cpu_pm_register();
 			cpus_read_unlock();
 			if (ret)
 				goto err_out;
-- 
2.17.1


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Re: [PATCH v2 1/2] coresight: cti: Add CPU Hotplug handling to CTI driver.

[Mathieu Poirier]

Hi Mike,

On Mon, May 04, 2020 at 05:15:29PM +0100, Mike Leach wrote:
> Adds registration of CPU start and stop functions to CPU hotplug
> mechanisms - for any CPU bound CTI.
> 
> Sets CTI powered flag according to state.
> Will enable CTI on CPU start if there are existing enable requests.
> 
> Signed-off-by: Mike Leach <mike.leach@linaro.org>
> ---
>  drivers/hwtracing/coresight/coresight-cti.c | 91 +++++++++++++++++++++
>  include/linux/cpuhotplug.h                  |  1 +
>  2 files changed, 92 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
> index be61c1705916..9af66719ae5b 100644
> --- a/drivers/hwtracing/coresight/coresight-cti.c
> +++ b/drivers/hwtracing/coresight/coresight-cti.c
> @@ -40,6 +40,12 @@ static DEFINE_MUTEX(ect_mutex);
>  #define csdev_to_cti_drvdata(csdev)	\
>  	dev_get_drvdata(csdev->dev.parent)
>  
> +/* power management handling */
> +static int nr_cti_cpu;
> +
> +/* quick lookup list for CPU bound CTIs when power handling */
> +static struct cti_drvdata *cti_cpu_drvdata[NR_CPUS];
> +
>  /*
>   * CTI naming. CTI bound to cores will have the name cti_cpu<N> where
>   * N is the CPU ID. System CTIs will have the name cti_sys<I> where I
> @@ -129,6 +135,35 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
>  	return rc;
>  }
>  
> +/* re-enable CTI on CPU when using CPU hotplug */
> +static void cti_cpuhp_enable_hw(struct cti_drvdata *drvdata)
> +{
> +	struct cti_config *config = &drvdata->config;
> +	struct device *dev = &drvdata->csdev->dev;
> +
> +	pm_runtime_get_sync(dev->parent);
> +	spin_lock(&drvdata->spinlock);
> +	config->hw_powered = true;
> +
> +	/* no need to do anything if no enable request */
> +	if (!atomic_read(&drvdata->config.enable_req_count))
> +		goto cti_hp_not_enabled;
> +
> +	/* try to claim the device */
> +	if (coresight_claim_device(drvdata->base))
> +		goto cti_hp_not_enabled;
> +
> +	cti_write_all_hw_regs(drvdata);
> +	config->hw_enabled = true;
> +	spin_unlock(&drvdata->spinlock);
> +	return;
> +
> +	/* did not re-enable due to no claim / no request */
> +cti_hp_not_enabled:
> +	spin_unlock(&drvdata->spinlock);
> +	pm_runtime_put(dev->parent);
> +}
> +
>  /* disable hardware */
>  static int cti_disable_hw(struct cti_drvdata *drvdata)
>  {
> @@ -620,6 +655,44 @@ static void cti_remove_conn_xrefs(struct cti_drvdata *drvdata)
>  	}
>  }
>  
> +/* CPU HP handlers */
> +static int cti_starting_cpu(unsigned int cpu)
> +{
> +	struct cti_drvdata *drvdata = cti_cpu_drvdata[cpu];
> +
> +	if (!drvdata)
> +		return 0;
> +
> +	cti_cpuhp_enable_hw(drvdata);
> +	return 0;
> +}
> +
> +static int cti_dying_cpu(unsigned int cpu)
> +{
> +	struct cti_drvdata *drvdata = cti_cpu_drvdata[cpu];
> +
> +	if (!drvdata)
> +		return 0;
> +
> +	spin_lock(&drvdata->spinlock);
> +	drvdata->config.hw_powered = false;
> +	coresight_disclaim_device(drvdata->base);
> +	spin_unlock(&drvdata->spinlock);
> +	return 0;
> +}
> +
> +/* release PM registrations */
> +static void cti_pm_release(struct cti_drvdata *drvdata)
> +{
> +	if (drvdata->ctidev.cpu >= 0) {
> +		if (--nr_cti_cpu == 0) {
> +			cpuhp_remove_state_nocalls(
> +				CPUHP_AP_ARM_CORESIGHT_CTI_STARTING);
> +		}
> +		cti_cpu_drvdata[drvdata->ctidev.cpu] = NULL;
> +	}
> +}
> +
>  /** cti ect operations **/
>  int cti_enable(struct coresight_device *csdev)
>  {
> @@ -655,6 +728,7 @@ static void cti_device_release(struct device *dev)
>  
>  	mutex_lock(&ect_mutex);
>  	cti_remove_conn_xrefs(drvdata);
> +	cti_pm_release(drvdata);
>  
>  	/* remove from the list */
>  	list_for_each_entry_safe(ect_item, ect_tmp, &ect_net, node) {
> @@ -730,6 +804,22 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
>  		goto err_out;
>  	}
>  
> +	/* setup CPU power management handling for CPU bound CTI devices. */
> +	if (drvdata->ctidev.cpu >= 0) {
> +		cti_cpu_drvdata[drvdata->ctidev.cpu] = drvdata;
> +		if (!nr_cti_cpu++) {
> +			cpus_read_lock();
> +			cpuhp_setup_state_nocalls_cpuslocked(

                        ret = cpuhp_setup_state_nocalls_cpuslocked(

Otherwise this patch looks good to me (many thanks for splitting).  On your next
revision please CC Thomas Gleixner as suggested by the get_maintainer.pl script.

Mathieu

> +				CPUHP_AP_ARM_CORESIGHT_CTI_STARTING,
> +				"arm/coresight_cti:starting",
> +				cti_starting_cpu, cti_dying_cpu);
> +
> +			cpus_read_unlock();
> +			if (ret)
> +				goto err_out;
> +		}
> +	}
> +
>  	/* create dynamic attributes for connections */
>  	ret = cti_create_cons_sysfs(dev, drvdata);
>  	if (ret) {
> @@ -768,6 +858,7 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
>  	return 0;
>  
>  err_out:
> +	cti_pm_release(drvdata);
>  	return ret;
>  }
>  
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 77d70b633531..6dc7332307ca 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -142,6 +142,7 @@ enum cpuhp_state {
>  	CPUHP_AP_ARM_XEN_STARTING,
>  	CPUHP_AP_ARM_KVMPV_STARTING,
>  	CPUHP_AP_ARM_CORESIGHT_STARTING,
> +	CPUHP_AP_ARM_CORESIGHT_CTI_STARTING,
>  	CPUHP_AP_ARM64_ISNDEP_STARTING,
>  	CPUHP_AP_SMPCFD_DYING,
>  	CPUHP_AP_X86_TBOOT_DYING,
> -- 
> 2.17.1
> 

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Re: [PATCH v2 2/2] coresight: cti: Add CPU idle pm notifer to CTI devices.

[Mathieu Poirier]

On Mon, May 04, 2020 at 05:15:30PM +0100, Mike Leach wrote:
> Adds a notify callback for CPU PM events to the CTI driver - for
> CPU bound CTI devices.
> 
> Signed-off-by: Mike Leach <mike.leach@linaro.org>
> ---
>  drivers/hwtracing/coresight/coresight-cti.c | 82 +++++++++++++++++++++
>  1 file changed, 82 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
> index 9af66719ae5b..0f0c14528701 100644
> --- a/drivers/hwtracing/coresight/coresight-cti.c
> +++ b/drivers/hwtracing/coresight/coresight-cti.c
> @@ -8,6 +8,7 @@
>  #include <linux/atomic.h>
>  #include <linux/bits.h>
>  #include <linux/coresight.h>
> +#include <linux/cpu_pm.h>
>  #include <linux/device.h>
>  #include <linux/io.h>
>  #include <linux/kernel.h>
> @@ -655,6 +656,84 @@ static void cti_remove_conn_xrefs(struct cti_drvdata *drvdata)
>  	}
>  }
>  
> +/** cti PM callbacks **/
> +static int cti_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd,
> +			     void *v)
> +{
> +	struct cti_drvdata *drvdata;
> +	unsigned int cpu = smp_processor_id();
> +	int notify_res = NOTIFY_OK;
> +
> +	if (!cti_cpu_drvdata[cpu])
> +		return NOTIFY_OK;
> +
> +	drvdata = cti_cpu_drvdata[cpu];
> +
> +	if (WARN_ON_ONCE(drvdata->ctidev.cpu != cpu))
> +		return NOTIFY_BAD;
> +
> +	spin_lock(&drvdata->spinlock);
> +
> +	switch (cmd) {
> +	case CPU_PM_ENTER:
> +		/* CTI regs all static - we have a copy & nothing to save */
> +		drvdata->config.hw_powered = false;
> +		if (drvdata->config.hw_enabled)
> +			coresight_disclaim_device(drvdata->base);
> +		break;
> +
> +	case CPU_PM_ENTER_FAILED:
> +		drvdata->config.hw_powered = true;
> +		if (drvdata->config.hw_enabled) {
> +			if (coresight_claim_device(drvdata->base))
> +				drvdata->config.hw_enabled = false;
> +		}
> +		break;
> +
> +	case CPU_PM_EXIT:
> +		/* write hardware registers to re-enable. */
> +		drvdata->config.hw_powered = true;
> +		drvdata->config.hw_enabled = false;
> +
> +		/* check enable reference count to enable HW */
> +		if (atomic_read(&drvdata->config.enable_req_count)) {
> +			/* check we can claim the device as we re-power */
> +			if (coresight_claim_device(drvdata->base))
> +				goto cti_notify_exit;
> +
> +			drvdata->config.hw_enabled = true;
> +			cti_write_all_hw_regs(drvdata);
> +		}
> +		break;
> +
> +	default:
> +		notify_res = NOTIFY_DONE;
> +		break;
> +	}
> +
> +cti_notify_exit:
> +	spin_unlock(&drvdata->spinlock);
> +	return notify_res;
> +}
> +
> +static struct notifier_block cti_cpu_pm_nb = {
> +	.notifier_call = cti_cpu_pm_notify,
> +};
> +
> +static int cti_cpu_pm_register(void)
> +{
> +	if (IS_ENABLED(CONFIG_CPU_PM))
> +		return cpu_pm_register_notifier(&cti_cpu_pm_nb);

Looking further into function cpu_pm_register_notifier(), it simply returns '0'
if CONFIG_CPU_PM is not defined.  As such cpu_pm_register_notifier() can be
called directly from cti_probe().  The same applies to
cpu_pm_unregister_notifier().

> +
> +	return 0;
> +}
> +
> +static void cti_cpu_pm_unregister(void)
> +{
> +	if (IS_ENABLED(CONFIG_CPU_PM))
> +		cpu_pm_unregister_notifier(&cti_cpu_pm_nb);
> +}
> +
>  /* CPU HP handlers */
>  static int cti_starting_cpu(unsigned int cpu)
>  {
> @@ -686,6 +765,8 @@ static void cti_pm_release(struct cti_drvdata *drvdata)
>  {
>  	if (drvdata->ctidev.cpu >= 0) {
>  		if (--nr_cti_cpu == 0) {
> +			cti_cpu_pm_unregister();
> +
>  			cpuhp_remove_state_nocalls(
>  				CPUHP_AP_ARM_CORESIGHT_CTI_STARTING);
>  		}
> @@ -814,6 +895,7 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
>  				"arm/coresight_cti:starting",
>  				cti_starting_cpu, cti_dying_cpu);
>  
> +			ret = cti_cpu_pm_register();

This should be one only if cpuhp_remove_state_nocalls() hasn't returned an
error.

Otherwise this looks good.

Thanks,
Mathieu

>  			cpus_read_unlock();
>  			if (ret)
>  				goto err_out;
> -- 
> 2.17.1
> 

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