Subject: Re: [PATCH v8 10/24] coresight: etm4x: allow etm4x to be built as a module

From: Tingwei Zhang <[email-masked]>
Date: Fri, 14 Aug 2020 07:57:41 +0800

On Fri, Aug 14, 2020 at 03:45:06AM +0800, Mathieu Poirier wrote:
> On Fri, Aug 07, 2020 at 07:11:39PM +0800, Tingwei Zhang wrote:
> > From: Kim Phillips <[email-masked]>
> > 
> > Allow to build coresight-etm4x as a module, for ease of development.
> > 
> > - Kconfig becomes a tristate, to allow =m
> > - append -core to source file name to allow module to
> >   be called coresight-etm4x by the Makefile
> > - add an etm4_remove function, for module unload
> > - add a MODULE_DEVICE_TABLE for autoloading on boot
> > - protect etmdrvdata[] with mutex lock from racing
> >   between module unload and CPU hotplug
> > 
> > Cc: Mathieu Poirier <[email-masked]>
> > Cc: Leo Yan <[email-masked]>
> > Cc: Alexander Shishkin <[email-masked]>
> > Cc: Randy Dunlap <[email-masked]>
> > Cc: Suzuki K Poulose <[email-masked]>
> > Cc: Greg Kroah-Hartman <[email-masked]>
> > Cc: Russell King <[email-masked]>
> > Signed-off-by: Kim Phillips <[email-masked]>
> > Signed-off-by: Tingwei Zhang <[email-masked]>
> > Tested-by: Mike Leach <[email-masked]>
> > ---
> >  drivers/hwtracing/coresight/Kconfig           |   5 +-
> >  drivers/hwtracing/coresight/Makefile          |   4 +-
> >  ...resight-etm4x.c => coresight-etm4x-core.c} | 118 +++++++++++++-----
> >  3 files changed, 92 insertions(+), 35 deletions(-)
> >  rename drivers/hwtracing/coresight/{coresight-etm4x.c =>
> coresight-etm4x-core.c} (95%)
> > 
> > diff --git a/drivers/hwtracing/coresight/Kconfig
> b/drivers/hwtracing/coresight/Kconfig
> > index 8fd9fd139cf3..d6e107bbd30b 100644
> > --- a/drivers/hwtracing/coresight/Kconfig
> > +++ b/drivers/hwtracing/coresight/Kconfig
> > @@ -78,7 +78,7 @@ config CORESIGHT_SOURCE_ETM3X
> >  	  module will be called coresight-etm3x.
> >  
> >  config CORESIGHT_SOURCE_ETM4X
> > -	bool "CoreSight Embedded Trace Macrocell 4.x driver"
> > +	tristate "CoreSight Embedded Trace Macrocell 4.x driver"
> >  	depends on ARM64
> >  	select CORESIGHT_LINKS_AND_SINKS
> >  	select PID_IN_CONTEXTIDR
> > @@ -88,6 +88,9 @@ config CORESIGHT_SOURCE_ETM4X
> >  	  for instruction level tracing. Depending on the implemented
> version
> >  	  data tracing may also be available.
> >  
> > +	  To compile this driver as a module, choose M here: the
> > +	  module will be called coresight-etm4x.
> > +
> >  config CORESIGHT_STM
> >  	tristate "CoreSight System Trace Macrocell driver"
> >  	depends on (ARM && !(CPU_32v3 || CPU_32v4 || CPU_32v4T)) || ARM64
> > diff --git a/drivers/hwtracing/coresight/Makefile
> b/drivers/hwtracing/coresight/Makefile
> > index d619cfd0abd8..271dc255454f 100644
> > --- a/drivers/hwtracing/coresight/Makefile
> > +++ b/drivers/hwtracing/coresight/Makefile
> > @@ -14,8 +14,8 @@ obj-$(CONFIG_CORESIGHT_LINKS_AND_SINKS) +=
> coresight-funnel.o \
> >  obj-$(CONFIG_CORESIGHT_SOURCE_ETM3X) += coresight-etm3x.o
> >  coresight-etm3x-y := coresight-etm3x-core.o coresight-etm-cp14.o \
> >  					coresight-etm3x-sysfs.o
> > -obj-$(CONFIG_CORESIGHT_SOURCE_ETM4X) += coresight-etm4x.o \
> > -					coresight-etm4x-sysfs.o
> > +obj-$(CONFIG_CORESIGHT_SOURCE_ETM4X) += coresight-etm4x.o
> > +coresight-etm4x-y := coresight-etm4x-core.o coresight-etm4x-sysfs.o
> >  obj-$(CONFIG_CORESIGHT_STM) += coresight-stm.o
> >  obj-$(CONFIG_CORESIGHT_CPU_DEBUG) += coresight-cpu-debug.o
> >  obj-$(CONFIG_CORESIGHT_CATU) += coresight-catu.o
> > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c
> b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> > similarity index 95%
> > rename from drivers/hwtracing/coresight/coresight-etm4x.c
> > rename to drivers/hwtracing/coresight/coresight-etm4x-core.c
> > index fddfd93b9a7b..ae9847e194a3 100644
> > --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> > @@ -48,6 +48,7 @@ module_param(pm_save_enable, int, 0444);
> >  MODULE_PARM_DESC(pm_save_enable,
> >  	"Save/restore state on power down: 1 = never, 2 = self-hosted");
> >  
> > +static DEFINE_PER_CPU(struct mutex, etmdrvdata_lock);
> >  static struct etmv4_drvdata *etmdrvdata[NR_CPUS];
> >  static void etm4_set_default_config(struct etmv4_config *config);
> >  static int etm4_set_event_filters(struct etmv4_drvdata *drvdata,
> > @@ -1089,18 +1090,25 @@ void etm4_config_trace_mode(struct etmv4_config
> *config)
> >  
> >  static int etm4_online_cpu(unsigned int cpu)
> >  {
> > -	if (!etmdrvdata[cpu])
> > +	mutex_lock(&per_cpu(etmdrvdata_lock, cpu));
> > +	if (!etmdrvdata[cpu]) {
> > +		mutex_unlock(&per_cpu(etmdrvdata_lock, cpu));
> >  		return 0;
> > +	}
> >  
> >  	if (etmdrvdata[cpu]->boot_enable &&
> !etmdrvdata[cpu]->sticky_enable)
> >  		coresight_enable(etmdrvdata[cpu]->csdev);
> > +	mutex_unlock(&per_cpu(etmdrvdata_lock, cpu));
> >  	return 0;
> >  }
> >  
> >  static int etm4_starting_cpu(unsigned int cpu)
> >  {
> > -	if (!etmdrvdata[cpu])
> > +	mutex_lock(&per_cpu(etmdrvdata_lock, cpu));
> > +	if (!etmdrvdata[cpu]) {
> > +		mutex_unlock(&per_cpu(etmdrvdata_lock, cpu));
> >  		return 0;
> > +	}
> >  
> >  	spin_lock(&etmdrvdata[cpu]->spinlock);
> >  	if (!etmdrvdata[cpu]->os_unlock)
> > @@ -1109,18 +1117,23 @@ static int etm4_starting_cpu(unsigned int cpu)
> >  	if (local_read(&etmdrvdata[cpu]->mode))
> >  		etm4_enable_hw(etmdrvdata[cpu]);
> >  	spin_unlock(&etmdrvdata[cpu]->spinlock);
> > +	mutex_unlock(&per_cpu(etmdrvdata_lock, cpu));
> >  	return 0;
> >  }
> >  
> >  static int etm4_dying_cpu(unsigned int cpu)
> >  {
> > -	if (!etmdrvdata[cpu])
> > +	mutex_lock(&per_cpu(etmdrvdata_lock, cpu));
> > +	if (!etmdrvdata[cpu]) {
> > +		mutex_unlock(&per_cpu(etmdrvdata_lock, cpu));
> >  		return 0;
> > +	}
> >  
> >  	spin_lock(&etmdrvdata[cpu]->spinlock);
> >  	if (local_read(&etmdrvdata[cpu]->mode))
> >  		etm4_disable_hw(etmdrvdata[cpu]);
> >  	spin_unlock(&etmdrvdata[cpu]->spinlock);
> > +	mutex_unlock(&per_cpu(etmdrvdata_lock, cpu));
> >  	return 0;
> >  }
> >  
> > @@ -1360,24 +1373,30 @@ static int etm4_cpu_pm_notify(struct
> notifier_block *nb, unsigned long cmd,
> >  {
> >  	struct etmv4_drvdata *drvdata;
> >  	unsigned int cpu = smp_processor_id();
> > +	int ret = NOTIFY_OK;
> >  
> > +	mutex_lock(&per_cpu(etmdrvdata_lock, cpu));
> >  	if (!etmdrvdata[cpu])
> > -		return NOTIFY_OK;
> > +		goto out;
> >  
> >  	drvdata = etmdrvdata[cpu];
> >  
> >  	if (!drvdata->save_state)
> > -		return NOTIFY_OK;
> > +		goto out;
> >  
> > -	if (WARN_ON_ONCE(drvdata->cpu != cpu))
> > -		return NOTIFY_BAD;
> > +	if (WARN_ON_ONCE(drvdata->cpu != cpu)) {
> > +		ret = NOTIFY_BAD;
> > +		goto out;
> > +	}
> >  
> >  	switch (cmd) {
> >  	case CPU_PM_ENTER:
> >  		/* save the state if self-hosted coresight is in use */
> >  		if (local_read(&drvdata->mode))
> > -			if (etm4_cpu_save(drvdata))
> > -				return NOTIFY_BAD;
> > +			if (etm4_cpu_save(drvdata)) {
> > +				ret = NOTIFY_BAD;
> > +				goto out;
> > +			}
> >  		break;
> >  	case CPU_PM_EXIT:
> >  		/* fallthrough */
> > @@ -1386,10 +1405,12 @@ static int etm4_cpu_pm_notify(struct
> notifier_block *nb, unsigned long cmd,
> >  			etm4_cpu_restore(drvdata);
> >  		break;
> >  	default:
> > -		return NOTIFY_DONE;
> > +		goto out;
> >  	}
> >  
> > -	return NOTIFY_OK;
> > +out:
> > +	mutex_unlock(&per_cpu(etmdrvdata_lock, cpu));
> > +	return ret;
> >  }
> >  
> >  static struct notifier_block etm4_cpu_pm_nb = {
> > @@ -1430,7 +1451,7 @@ static int __init etm4_pm_setup(void)
> >  	return ret;
> >  }
> >  
> > -static void __init etm4_pm_clear(void)
> > +static void etm4_pm_clear(void)
> >  {
> >  	cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
> >  	cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
> > @@ -1487,25 +1508,20 @@ static int etm4_probe(struct amba_device *adev,
> const struct amba_id *id)
> >  	if (!desc.name)
> >  		return -ENOMEM;
> >  
> > -	etmdrvdata[drvdata->cpu] = drvdata;
> > -
> >  	if (smp_call_function_single(drvdata->cpu,
> >  				etm4_init_arch_data,  drvdata, 1))
> >  		dev_err(dev, "ETM arch init failed\n");
> >  
> > -	if (etm4_arch_supported(drvdata->arch) == false) {
> > -		ret = -EINVAL;
> > -		goto err_arch_supported;
> > -	}
> > +	if (etm4_arch_supported(drvdata->arch) == false)
> > +		return -EINVAL;
> >  
> >  	etm4_init_trace_id(drvdata);
> >  	etm4_set_default(&drvdata->config);
> >  
> >  	pdata = coresight_get_platform_data(dev);
> > -	if (IS_ERR(pdata)) {
> > -		ret = PTR_ERR(pdata);
> > -		goto err_arch_supported;
> > -	}
> > +	if (IS_ERR(pdata))
> > +		return PTR_ERR(pdata);
> > +
> >  	adev->dev.platform_data = pdata;
> >  
> >  	desc.type = CORESIGHT_DEV_TYPE_SOURCE;
> > @@ -1515,17 +1531,19 @@ static int etm4_probe(struct amba_device *adev,
> const struct amba_id *id)
> >  	desc.dev = dev;
> >  	desc.groups = coresight_etmv4_groups;
> >  	drvdata->csdev = coresight_register(&desc);
> > -	if (IS_ERR(drvdata->csdev)) {
> > -		ret = PTR_ERR(drvdata->csdev);
> > -		goto err_arch_supported;
> > -	}
> > +	if (IS_ERR(drvdata->csdev))
> > +		return PTR_ERR(drvdata->csdev);
> >  
> >  	ret = etm_perf_symlink(drvdata->csdev, true);
> >  	if (ret) {
> >  		coresight_unregister(drvdata->csdev);
> > -		goto err_arch_supported;
> > +		return ret;
> >  	}
> >  
> > +	mutex_lock(&per_cpu(etmdrvdata_lock, drvdata->cpu));
> > +	etmdrvdata[drvdata->cpu] = drvdata;
> > +	mutex_unlock(&per_cpu(etmdrvdata_lock, drvdata->cpu));
> > +
> >  	pm_runtime_put(&adev->dev);
> >  	dev_info(&drvdata->csdev->dev, "CPU%d: ETM v%d.%d initialized\n",
> >  		 drvdata->cpu, drvdata->arch >> 4, drvdata->arch & 0xf);
> > @@ -1536,10 +1554,6 @@ static int etm4_probe(struct amba_device *adev,
> const struct amba_id *id)
> >  	}
> >  
> >  	return 0;
> > -
> > -err_arch_supported:
> > -	etmdrvdata[drvdata->cpu] = NULL;
> > -	return ret;
> >  }
> >  
> >  static struct amba_cs_uci_id uci_id_etm4[] = {
> > @@ -1551,6 +1565,22 @@ static struct amba_cs_uci_id uci_id_etm4[] = {
> >  	}
> >  };
> >  
> > +static int __exit etm4_remove(struct amba_device *adev)
> > +{
> > +	struct etmv4_drvdata *drvdata = dev_get_drvdata(&adev->dev);
> > +
> > +	etm_perf_symlink(drvdata->csdev, false);
> > +
> > +	mutex_lock(&per_cpu(etmdrvdata_lock, drvdata->cpu));
> > +	etmdrvdata[drvdata->cpu] = NULL;
> > +	mutex_unlock(&per_cpu(etmdrvdata_lock, drvdata->cpu));
> > +
> > +	coresight_unregister(drvdata->csdev);
> > +
> > +	return 0;
> > +}
> > +
> > +
> 
> Extra line
> 

Will fix in next revision.

> >  static const struct amba_id etm4_ids[] = {
> >  	CS_AMBA_ID(0x000bb95d),			/* Cortex-A53 */
> >  	CS_AMBA_ID(0x000bb95e),			/* Cortex-A57 */
> > @@ -1568,18 +1598,26 @@ static const struct amba_id etm4_ids[] = {
> >  	{},
> >  };
> >  
> > +MODULE_DEVICE_TABLE(amba, etm4_ids);
> > +
> >  static struct amba_driver etm4x_driver = {
> >  	.drv = {
> >  		.name   = "coresight-etm4x",
> > +		.owner  = THIS_MODULE,
> >  		.suppress_bind_attrs = true,
> >  	},
> >  	.probe		= etm4_probe,
> > +	.remove         = etm4_remove,
> >  	.id_table	= etm4_ids,
> >  };
> >  
> >  static int __init etm4x_init(void)
> >  {
> >  	int ret;
> > +	int cpu;
> > +
> > +	for_each_possible_cpu(cpu)
> > +		mutex_init(&per_cpu(etmdrvdata_lock, cpu));
> >  
> >  	ret = etm4_pm_setup();
> >  
> > @@ -1595,4 +1633,20 @@ static int __init etm4x_init(void)
> >  
> >  	return ret;
> >  }
> > -device_initcall(etm4x_init);
> > +
> > +static void __exit etm4x_exit(void)
> > +{
> > +	int cpu;
> > +
> > +	amba_driver_unregister(&etm4x_driver);
> > +	etm4_pm_clear();
> > +	for_each_possible_cpu(cpu)
> > +		mutex_destroy(&per_cpu(etmdrvdata_lock, cpu));
> > +}
> > +module_init(etm4x_init);
> > +module_exit(etm4x_exit);
> > +
> > +MODULE_AUTHOR("Pratik Patel <[email-masked]>");
> > +MODULE_AUTHOR("Mathieu Poirier <[email-masked]>");
> > +MODULE_DESCRIPTION("Arm CoreSight Program Flow Trace v4 driver");
> > +MODULE_LICENSE("GPL v2");
> > -- 
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum,
> > a Linux Foundation Collaborative Project
> > 

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