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

On Fri, Aug 07, 2020 at 07:11:39PM +0800, Tingwei Zhang wrote:

From: Kim Phillips kim.phillips@arm.com

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 mathieu.poirier@linaro.org Cc: Leo Yan leo.yan@linaro.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Randy Dunlap rdunlap@infradead.org Cc: Suzuki K Poulose Suzuki.Poulose@arm.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Russell King linux@armlinux.org.uk Signed-off-by: Kim Phillips kim.phillips@arm.com Signed-off-by: Tingwei Zhang tingwei@codeaurora.org Tested-by: Mike Leach mike.leach@linaro.org

---

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));

Ouch!

A mutex wrapping a spinlock to protect the exact same drvdata structure. Because etmdrvdata_lock[] is a per cpu variable I suggest to get rid of drvdata::spinlock altogether. To do so:

1) In etm4_enable_sysfs(), get rid of the spinlock/unlock(). 2) In etm4_enable_hw_smp_call(), grab the mutex based on the value of drvdata->cpu and set drvdata->stick_enable based on the return value of etm4_enable_hw() while holding the mutex. 3) In etm4_disable_sysfs(), just change spinlock/unlock to mutex operations. 4) Get rid of spinlock operations in etm4_starting/dying_cpu().

As Suzuki pointed out the same kind of gymnastic needs to be done for ETMv3.

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;

+}

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 pratikp@codeaurora.org"); +MODULE_AUTHOR("Mathieu Poirier mathieu.poirier@linaro.org"); +MODULE_DESCRIPTION("Arm CoreSight Program Flow Trace v4 driver");

+MODULE_LICENSE("GPL v2");

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