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

Allow to build coresight-tmc 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-tmc by the Makefile
- add an tmc_remove function, for module unload
- 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/20200928163513.70169-14-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/Kconfig

@@ -25,7 +25,8 @@ config CORESIGHT_LINKS_AND_SINKS
 	  entity at run time to form a complete trace path.
 
 config CORESIGHT_LINK_AND_SINK_TMC
-	bool "Coresight generic TMC driver"
+	tristate "Coresight generic TMC driver"
+
 	depends on CORESIGHT_LINKS_AND_SINKS
 	help
 	  This enables support for the Trace Memory Controller driver.
@@ -34,6 +35,9 @@ config CORESIGHT_LINK_AND_SINK_TMC
 	  complies with the generic implementation of the component without
 	  special enhancement or added features.
 
+	  To compile this driver as a module, choose M here: the
+	  module will be called coresight-tmc.
+
 config CORESIGHT_CATU
 	bool "Coresight Address Translation Unit (CATU) driver"
 	depends on CORESIGHT_LINK_AND_SINK_TMC

drivers/hwtracing/coresight/Makefile

@@ -4,8 +4,8 @@
 #
 obj-$(CONFIG_CORESIGHT) += coresight.o coresight-etm-perf.o \
 			   coresight-platform.o coresight-sysfs.o
-obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o \
+obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o
-					     coresight-tmc-etf.o \
+coresight-tmc-y := coresight-tmc-core.o coresight-tmc-etf.o \
 		      coresight-tmc-etr.o
 obj-$(CONFIG_CORESIGHT_SINK_TPIU) += coresight-tpiu.o
 obj-$(CONFIG_CORESIGHT_SINK_ETBV10) += coresight-etb10.o

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

@@ -559,6 +559,21 @@ out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 }
 
+static int __exit tmc_remove(struct amba_device *adev)
+{
+	struct tmc_drvdata *drvdata = dev_get_drvdata(&adev->dev);
+
+	/*
+	 * Since misc_open() holds a refcount on the f_ops, which is
+	 * etb fops in this case, device is there until last file
+	 * handler to this device is closed.
+	 */
+	misc_deregister(&drvdata->miscdev);
+	coresight_unregister(drvdata->csdev);
+
+	return 0;
+}
+
 static const struct amba_id tmc_ids[] = {
 	CS_AMBA_ID(0x000bb961),
 	/* Coresight SoC 600 TMC-ETR/ETS */
@@ -570,6 +585,8 @@ static const struct amba_id tmc_ids[] = {
 	{ 0, 0},
 };
 
+MODULE_DEVICE_TABLE(amba, tmc_ids);
+
 static struct amba_driver tmc_driver = {
 	.drv = {
 		.name   = "coresight-tmc",
@@ -578,6 +595,12 @@ static struct amba_driver tmc_driver = {
 	},
 	.probe		= tmc_probe,
 	.shutdown	= tmc_shutdown,
+	.remove		= tmc_remove,
 	.id_table	= tmc_ids,
 };
-builtin_amba_driver(tmc_driver);
+
+module_amba_driver(tmc_driver);
+
+MODULE_AUTHOR("Pratik Patel <pratikp@codeaurora.org>");
+MODULE_DESCRIPTION("Arm CoreSight Trace Memory Controller driver");
+MODULE_LICENSE("GPL v2");