coresight: etm4x: Allow etm4x to be built as a module

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
- delay advertising the per-cpu etmdrvdata
- protect etmdrvdata[] by modifying it on relevant CPU

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>
Tested-by: Mike Leach <mike.leach@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Kim Phillips <kim.phillips@arm.com>
Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200928163513.70169-11-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

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

drivers/hwtracing/coresight/coresight-etm4x-core.c

@@ -1447,7 +1447,7 @@ unregister_notifier:
 	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);
@@ -1504,25 +1504,20 @@ 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;
@@ -1532,17 +1527,17 @@ 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;
 	}
 
+	etmdrvdata[drvdata->cpu] = drvdata;
+
 	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);
@@ -1553,10 +1548,6 @@ 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[] = {
@@ -1568,6 +1559,40 @@ static struct amba_cs_uci_id uci_id_etm4[] = {
 	}
 };
 
+static void __exit clear_etmdrvdata(void *info)
+{
+	int cpu = *(int *)info;
+
+	etmdrvdata[cpu] = NULL;
+}
+
+static int __exit etm4_remove(struct amba_device *adev)
+{
+	struct etmv4_drvdata *drvdata = dev_get_drvdata(&adev->dev);
+
+	etm_perf_symlink(drvdata->csdev, false);
+
+	/*
+	 * Taking hotplug lock here to avoid racing between etm4_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;
+}
+
 static const struct amba_id etm4_ids[] = {
 	CS_AMBA_ID(0x000bb95d),			/* Cortex-A53 */
 	CS_AMBA_ID(0x000bb95e),			/* Cortex-A57 */
@@ -1587,12 +1612,16 @@ 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,
 };
 
@@ -1614,4 +1643,17 @@ static int __init etm4x_init(void)
 
 	return ret;
 }
-device_initcall(etm4x_init);
+
+static void __exit etm4x_exit(void)
+{
+	amba_driver_unregister(&etm4x_driver);
+	etm4_pm_clear();
+}
+
+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.x driver");
+MODULE_LICENSE("GPL v2");