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

[Mathieu Poirier <mathieu.poirier@linaro.org>]

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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