Message-ID: <20200915180918.GA3665622@xps15>
Date:   Tue, 15 Sep 2020 12:09:18 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Tingwei Zhang <tingwei@...eaurora.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mike Leach <mike.leach@...aro.org>,
        Kim Phillips <kim.phillips@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Leo Yan <leo.yan@...aro.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Russell King <linux@...linux.org.uk>,
        Mian Yousaf Kaukab <ykaukab@...e.de>, tsoni@...eaurora.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Mao Jinlong <jinlmao@...eaurora.org>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 09/24] coresight: etm3x: allow etm3x to be built as a
 module

On Tue, Sep 15, 2020 at 06:41:01PM +0800, Tingwei Zhang wrote:
> From: Kim Phillips <kim.phillips@....com>
> 
> Allow to build coresight-etm3x 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-etm3x by the Makefile
> - add an etm_remove function, for module unload
> - add a MODULE_DEVICE_TABLE for autoloading on boot
> - delay advertising the per-cpu etmdrvdata
> - protect etmdrvdata[] by modifying it on relevant CPU
> 
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Leo Yan <leo.yan@...aro.org>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Cc: Suzuki K Poulose <Suzuki.Poulose@....com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Russell King <linux@...linux.org.uk>
> Signed-off-by: Kim Phillips <kim.phillips@....com>
> Signed-off-by: Tingwei Zhang <tingwei@...eaurora.org>
> Reviewed-by: Mike Leach <mike.leach@...aro.org>
> ---
>  drivers/hwtracing/coresight/Kconfig           |   5 +-
>  drivers/hwtracing/coresight/Makefile          |   5 +-
>  ...resight-etm3x.c => coresight-etm3x-core.c} | 148 ++++++++++++++----
>  3 files changed, 122 insertions(+), 36 deletions(-)
>  rename drivers/hwtracing/coresight/{coresight-etm3x.c => coresight-etm3x-core.c} (90%)
> 
> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
> index 6433f835fc97..8fd9fd139cf3 100644
> --- a/drivers/hwtracing/coresight/Kconfig
> +++ b/drivers/hwtracing/coresight/Kconfig
> @@ -65,7 +65,7 @@ config CORESIGHT_SINK_ETBV10
>  	  special enhancement or added features.
>  
>  config CORESIGHT_SOURCE_ETM3X
> -	bool "CoreSight Embedded Trace Macrocell 3.x driver"
> +	tristate "CoreSight Embedded Trace Macrocell 3.x driver"
>  	depends on !ARM64
>  	select CORESIGHT_LINKS_AND_SINKS
>  	help
> @@ -74,6 +74,9 @@ config CORESIGHT_SOURCE_ETM3X
>  	  This is primarily useful for instruction level tracing.  Depending
>  	  the ETM version data tracing may also be available.
>  
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called coresight-etm3x.
> +
>  config CORESIGHT_SOURCE_ETM4X
>  	bool "CoreSight Embedded Trace Macrocell 4.x driver"
>  	depends on ARM64
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index 19497d1d92bf..86b4648844b4 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -11,8 +11,9 @@ obj-$(CONFIG_CORESIGHT_SINK_TPIU) += coresight-tpiu.o
>  obj-$(CONFIG_CORESIGHT_SINK_ETBV10) += coresight-etb10.o
>  obj-$(CONFIG_CORESIGHT_LINKS_AND_SINKS) += coresight-funnel.o \
>  					   coresight-replicator.o
> -obj-$(CONFIG_CORESIGHT_SOURCE_ETM3X) += coresight-etm3x.o coresight-etm-cp14.o \
> -					coresight-etm3x-sysfs.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_STM) += coresight-stm.o
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
> similarity index 90%
> rename from drivers/hwtracing/coresight/coresight-etm3x.c
> rename to drivers/hwtracing/coresight/coresight-etm3x-core.c
> index bf22dcfd3327..56eba0b5c71f 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
> @@ -782,6 +782,42 @@ static void etm_init_trace_id(struct etm_drvdata *drvdata)
>  	drvdata->traceid = coresight_get_trace_id(drvdata->cpu);
>  }
>  
> +static int __init etm_hp_setup(void)
> +{
> +	int ret;
> +
> +	ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING,
> +					     "arm/coresight:starting",
> +					     etm_starting_cpu, etm_dying_cpu);

Indentation problem.

> +
> +	if (ret)
> +		return ret;
> +
> +	ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN,
> +						   "arm/coresight:online",
> +						   etm_online_cpu, NULL);
> +
> +	/* HP dyn state ID returned in ret on success */
> +	if (ret > 0) {
> +		hp_online = ret;
> +		return 0;
> +	}
> +
> +	/* failed dyn state - remove others */
> +	cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
> +
> +	return ret;
> +}
> +
> +static void etm_hp_clear(void)
> +{
> +	cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
> +	if (hp_online) {
> +		cpuhp_remove_state_nocalls(hp_online);
> +		hp_online = 0;
> +	}
> +}
> +
>  static int etm_probe(struct amba_device *adev, const struct amba_id *id)
>  {
>  	int ret;
> @@ -824,38 +860,23 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
>  		return -ENOMEM;
>  
>  	cpus_read_lock();

Locking is no longer needed.

> -	etmdrvdata[drvdata->cpu] = drvdata;
>  
>  	if (smp_call_function_single(drvdata->cpu,
>  				     etm_init_arch_data,  drvdata, 1))
>  		dev_err(dev, "ETM arch init failed\n");
>  
> -	if (!etm_count++) {
> -		cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING,
> -						     "arm/coresight:starting",
> -						     etm_starting_cpu, etm_dying_cpu);
> -		ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN,
> -							   "arm/coresight:online",
> -							   etm_online_cpu, NULL);
> -		if (ret < 0)
> -			goto err_arch_supported;
> -		hp_online = ret;
> -	}
>  	cpus_read_unlock();
>  
> -	if (etm_arch_supported(drvdata->arch) == false) {
> -		ret = -EINVAL;
> -		goto err_arch_supported;
> -	}
> +	if (etm_arch_supported(drvdata->arch) == false)
> +		return -EINVAL;
>  
>  	etm_init_trace_id(drvdata);
>  	etm_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;
> @@ -865,17 +886,17 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
>  	desc.dev = dev;
>  	desc.groups = coresight_etm_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;
>  	}
>  
> +	etmdrvdata[drvdata->cpu] = drvdata;
> +
>  	pm_runtime_put(&adev->dev);
>  	dev_info(&drvdata->csdev->dev,
>  		 "%s initialized\n", (char *)coresight_get_uci_data(id));
> @@ -885,14 +906,40 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
>  	}
>  
>  	return 0;
> +}
>  
> -err_arch_supported:
> -	if (--etm_count == 0) {
> -		cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
> -		if (hp_online)
> -			cpuhp_remove_state_nocalls(hp_online);
> -	}
> -	return ret;
> +static void __exit clear_etmdrvdata(void *info)
> +{
> +	int cpu = *(int *)info;
> +
> +	etmdrvdata[cpu] = NULL;
> +}
> +
> +static int __exit etm_remove(struct amba_device *adev)
> +{
> +	struct etm_drvdata *drvdata = dev_get_drvdata(&adev->dev);
> +
> +	etm_perf_symlink(drvdata->csdev, false);
> +
> +	/*
> +	 * Taking hotplug lock here to avoid racing between etm_remove and
> +	 * CPU hotplug call backs.
> +	 */
> +	cpus_read_lock();
> +	/*
> +	 * The readers for etmdrvdata[] are CPU hotplug call backs
> +	 * and PM notification call backs. Change etmdrvdata[i] on
> +	 * CPU i ensures these call backs has consistent view
> +	 * inside one call back function.
> +	 */
> +	if (smp_call_function_single(drvdata->cpu, clear_etmdrvdata, &drvdata->cpu, 1))
> +		etmdrvdata[drvdata->cpu] = NULL;
> +
> +	cpus_read_unlock();
> +
> +	coresight_unregister(drvdata->csdev);
> +
> +	return 0;
>  }
>  
>  #ifdef CONFIG_PM
> @@ -937,6 +984,8 @@ static const struct amba_id etm_ids[] = {
>  	{ 0, 0},
>  };
>  
> +MODULE_DEVICE_TABLE(amba, etm_ids);
> +
>  static struct amba_driver etm_driver = {
>  	.drv = {
>  		.name	= "coresight-etm3x",
> @@ -945,6 +994,39 @@ static struct amba_driver etm_driver = {
>  		.suppress_bind_attrs = true,
>  	},
>  	.probe		= etm_probe,
> +	.remove         = etm_remove,
>  	.id_table	= etm_ids,
>  };
> -builtin_amba_driver(etm_driver);
> +
> +static int __init etm_init(void)
> +{
> +	int ret;
> +
> +	ret = etm_hp_setup();
> +
> +	/* etm_pm_setup() does its own cleanup - exit on error */

Copy/paste error --> s/etm_pm_setup/etm_hp_setup

> +	if (ret)
> +		return ret;
> +
> +	ret = amba_driver_register(&etm_driver);
> +	if (ret) {
> +		pr_err("Error registering etm3x driver\n");
> +		etm_hp_clear();
> +	}
> +
> +	return ret;
> +}
> +
> +static void __exit etm_exit(void)
> +{
> +	amba_driver_unregister(&etm_driver);
> +	etm_hp_clear();
> +}
> +
> +module_init(etm_init);
> +module_exit(etm_exit);
> +
> +MODULE_AUTHOR("Pratik Patel <pratikp@...eaurora.org>");
> +MODULE_AUTHOR("Mathieu Poirier <mathieu.poirier@...aro.org>");
> +MODULE_DESCRIPTION("Arm CoreSight Program Flow Trace 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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