coresight: core: Allow the coresight core driver to be built as a module

Enhance coresight developer's efficiency to debug coresight drivers.
- Kconfig becomes a tristate, to allow =m
- append -core to source file name to allow module to
  be called coresight by the Makefile
- modules can have only one init/exit, so we add the etm_perf
  register/unregister function calls to the core init/exit
  functions.
- add a MODULE_DEVICE_TABLE for autoloading on boot

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/20200928163513.70169-25-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/Kconfig

@@ -3,7 +3,7 @@
 # Coresight configuration
 #
 menuconfig CORESIGHT
-	bool "CoreSight Tracing Support"
+	tristate "CoreSight Tracing Support"
 	depends on ARM || ARM64
 	depends on OF || ACPI
 	select ARM_AMBA
@@ -15,6 +15,9 @@ menuconfig CORESIGHT
 	  specification and configure the right series of components when a
 	  trace source gets enabled.
 
+	  To compile this driver as a module, choose M here: the
+	  module will be called coresight.
+
 if CORESIGHT
 config CORESIGHT_LINKS_AND_SINKS
 	tristate "CoreSight Link and Sink drivers"

drivers/hwtracing/coresight/Makefile

@@ -2,8 +2,9 @@
 #
 # Makefile for CoreSight drivers.
 #
-obj-$(CONFIG_CORESIGHT) += coresight.o coresight-etm-perf.o \
-			   coresight-platform.o coresight-sysfs.o
+obj-$(CONFIG_CORESIGHT) += coresight.o
+coresight-y := coresight-core.o  coresight-etm-perf.o coresight-platform.o \
+		coresight-sysfs.o
 obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o
 coresight-tmc-y := coresight-tmc-core.o coresight-tmc-etf.o \
 		      coresight-tmc-etr.o

drivers/hwtracing/coresight/coresight-core.c

@@ -1452,16 +1452,6 @@ int coresight_timeout(void __iomem *addr, u32 offset, int position, int value)
 }
 EXPORT_SYMBOL_GPL(coresight_timeout);
 
-struct bus_type coresight_bustype = {
-	.name	= "coresight",
-};
-
-static int __init coresight_init(void)
-{
-	return bus_register(&coresight_bustype);
-}
-postcore_initcall(coresight_init);
-
 /*
  * coresight_release_platform_data: Release references to the devices connected
  * to the output port of this device.
@@ -1670,3 +1660,35 @@ char *coresight_alloc_device_name(struct coresight_dev_list *dict,
 	return name;
 }
 EXPORT_SYMBOL_GPL(coresight_alloc_device_name);
+
+struct bus_type coresight_bustype = {
+	.name	= "coresight",
+};
+
+static int __init coresight_init(void)
+{
+	int ret;
+
+	ret = bus_register(&coresight_bustype);
+	if (ret)
+		return ret;
+
+	ret = etm_perf_init();
+	if (ret)
+		bus_unregister(&coresight_bustype);
+
+	return ret;
+}
+
+static void __exit coresight_exit(void)
+{
+	etm_perf_exit();
+	bus_unregister(&coresight_bustype);
+}
+
+module_init(coresight_init);
+module_exit(coresight_exit);
+
+MODULE_AUTHOR("Pratik Patel <pratikp@codeaurora.org>");
+MODULE_AUTHOR("Mathieu Poirier <mathieu.poirier@linaro.org>");
+MODULE_DESCRIPTION("Arm CoreSight tracer driver");

drivers/hwtracing/coresight/coresight-etm-perf.c

@@ -599,7 +599,7 @@ void etm_perf_del_symlink_sink(struct coresight_device *csdev)
 	csdev->ea = NULL;
 }
 
-static int __init etm_perf_init(void)
+int __init etm_perf_init(void)
 {
 	int ret;
 
@@ -626,4 +626,8 @@ static int __init etm_perf_init(void)
 
 	return ret;
 }
-device_initcall(etm_perf_init);
+
+void __exit etm_perf_exit(void)
+{
+	perf_pmu_unregister(&etm_pmu);
+}

drivers/hwtracing/coresight/coresight-etm-perf.h

@@ -82,4 +82,7 @@ static inline void *etm_perf_sink_config(struct perf_output_handle *handle)
 
 #endif /* CONFIG_CORESIGHT */
 
+int __init etm_perf_init(void);
+void __exit etm_perf_exit(void);
+
 #endif