[RFC PATCH] Change coresight tmc from misc device to cdev device

[Jay Chen <jkchen@linux.alibaba.com>]

For coresight in the server scenario, if there are too many
cpu cores and too many tmc peripherals, the error of insufficient
device numbers will occur by misc device

Signed-off-by: Jay Chen <jkchen@linux.alibaba.com>
---
 drivers/hwtracing/coresight/coresight-core.c  | 53 +++++++++++++++++++
 .../hwtracing/coresight/coresight-tmc-core.c  | 13 ++---
 drivers/hwtracing/coresight/coresight-tmc.h   |  4 +-
 include/linux/coresight.h                     | 23 ++++++++
 4 files changed, 83 insertions(+), 10 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 8a18c71df37a..b0cca3060f4e 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -17,6 +17,7 @@
 #include <linux/coresight.h>
 #include <linux/of_platform.h>
 #include <linux/delay.h>
+#include <linux/cdev.h>
 #include <linux/pm_runtime.h>
 
 #include "coresight-etm-perf.h"
@@ -1567,6 +1568,58 @@ void coresight_release_platform_data(struct coresight_device *csdev,
 		coresight_remove_conns_sysfs_group(csdev);
 }
 
+int coresight_cdev_register(struct coresight_cdev *cdev, const struct file_operations *fops,
+			    const char *name)
+{
+	struct device *device;
+
+	if (alloc_chrdev_region(&cdev->devno, 0, 1, name)) {
+		pr_err("failed to create the coresight cdev region\n");
+		return -EFAULT;
+	}
+
+	cdev->class = class_create(THIS_MODULE, name);
+	if (IS_ERR(cdev->class)) {
+		pr_err("failed to create the coresight class\n");
+		goto coresight_unregister_region;
+	}
+
+	cdev_init(&cdev->cdev, fops);
+	if (cdev_add(&cdev->cdev, cdev->devno, 1)) {
+		pr_err("failed to add the coresight cdev\n");
+		goto coresight_free_class;
+	}
+
+	device = device_create(cdev->class, NULL, cdev->devno,
+			       cdev, name);
+	if (IS_ERR(device)) {
+		pr_err("failed to create device for coresight\n");
+		goto coresight_del_cdev;
+	}
+
+	return 0;
+
+coresight_del_cdev:
+	cdev_del(&cdev->cdev);
+coresight_free_class:
+	class_destroy(cdev->class);
+coresight_unregister_region:
+	unregister_chrdev_region(cdev->devno, 1);
+
+	return -EFAULT;
+}
+EXPORT_SYMBOL_GPL(coresight_cdev_register);
+
+int coresight_cdev_unregister(struct coresight_cdev *cdev)
+{
+	device_destroy(cdev->class, cdev->devno);
+	cdev_del(&cdev->cdev);
+	class_destroy(cdev->class);
+	unregister_chrdev_region(cdev->devno, 1);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(coresight_cdev_unregister);
+
 struct coresight_device *coresight_register(struct coresight_desc *desc)
 {
 	int ret;
diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
index 74c6323d4d6a..c4aae8ff65eb 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
@@ -147,7 +147,7 @@ static int tmc_open(struct inode *inode, struct file *file)
 {
 	int ret;
 	struct tmc_drvdata *drvdata = container_of(file->private_data,
-						   struct tmc_drvdata, miscdev);
+						   struct tmc_drvdata, cdev);
 
 	ret = tmc_read_prepare(drvdata);
 	if (ret)
@@ -179,7 +179,7 @@ static ssize_t tmc_read(struct file *file, char __user *data, size_t len,
 	char *bufp;
 	ssize_t actual;
 	struct tmc_drvdata *drvdata = container_of(file->private_data,
-						   struct tmc_drvdata, miscdev);
+						   struct tmc_drvdata, cdev);
 	actual = tmc_get_sysfs_trace(drvdata, *ppos, len, &bufp);
 	if (actual <= 0)
 		return 0;
@@ -200,7 +200,7 @@ static int tmc_release(struct inode *inode, struct file *file)
 {
 	int ret;
 	struct tmc_drvdata *drvdata = container_of(file->private_data,
-						   struct tmc_drvdata, miscdev);
+						   struct tmc_drvdata, cdev);
 
 	ret = tmc_read_unprepare(drvdata);
 	if (ret)
@@ -529,10 +529,7 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 		goto out;
 	}
 
-	drvdata->miscdev.name = desc.name;
-	drvdata->miscdev.minor = MISC_DYNAMIC_MINOR;
-	drvdata->miscdev.fops = &tmc_fops;
-	ret = misc_register(&drvdata->miscdev);
+	ret = coresight_cdev_register(&drvdata->cdev, &tmc_fops, desc.name);
 	if (ret)
 		coresight_unregister(drvdata->csdev);
 	else
@@ -572,7 +569,7 @@ static void tmc_remove(struct amba_device *adev)
 	 * etb fops in this case, device is there until last file
 	 * handler to this device is closed.
 	 */
-	misc_deregister(&drvdata->miscdev);
+	coresight_cdev_unregister(&drvdata->cdev);
 	coresight_unregister(drvdata->csdev);
 }
 
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index b91ec7dde7bc..c37e2ed1cb9d 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -166,7 +166,7 @@ struct etr_buf {
  * struct tmc_drvdata - specifics associated to an TMC component
  * @base:	memory mapped base address for this component.
  * @csdev:	component vitals needed by the framework.
- * @miscdev:	specifics to handle "/dev/xyz.tmc" entry.
+ * @cdev:	specifics to handle "/dev/xyz.tmc" entry.
  * @spinlock:	only one at a time pls.
  * @pid:	Process ID of the process being monitored by the session
  *		that is using this component.
@@ -188,7 +188,7 @@ struct etr_buf {
 struct tmc_drvdata {
 	void __iomem		*base;
 	struct coresight_device	*csdev;
-	struct miscdevice	miscdev;
+	struct coresight_cdev	cdev;
 	spinlock_t		spinlock;
 	pid_t			pid;
 	bool			reading;
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index 93a2922b7653..aebe8b8327ad 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -9,6 +9,7 @@
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/perf_event.h>
+#include <linux/cdev.h>
 #include <linux/sched.h>
 
 /* Peripheral id registers (0xFD0-0xFEC) */
@@ -252,6 +253,12 @@ struct coresight_device {
 	void *active_cscfg_ctxt;
 };
 
+struct coresight_cdev {
+	dev_t devno;
+	struct class *class;
+	struct cdev cdev;
+};
+
 /*
  * coresight_dev_list - Mapping for devices to "name" index for device
  * names.
@@ -506,6 +513,10 @@ void coresight_relaxed_write64(struct coresight_device *csdev,
 			       u64 val, u32 offset);
 void coresight_write64(struct coresight_device *csdev, u64 val, u32 offset);
 
+int coresight_cdev_register(struct coresight_cdev *cdev, const struct file_operations *fops,
+			const char *name);
+
+int coresight_cdev_unregister(struct coresight_cdev *cdev);
 #else
 static inline struct coresight_device *
 coresight_register(struct coresight_desc *desc) { return NULL; }
@@ -581,6 +592,18 @@ static inline void coresight_write64(struct coresight_device *csdev, u64 val, u3
 {
 }
 
+static inline int coresight_cdev_register(struct coresight_cdev *cdev,
+					  const struct file_operations *fops,
+					  const char *name)
+{
+	return 0;
+}
+
+static inline int coresight_cdev_unregister(struct coresight_cdev *cdev)
+{
+	return 0;
+}
+
 #endif		/* IS_ENABLED(CONFIG_CORESIGHT) */
 
 extern int coresight_get_cpu(struct device *dev);
-- 
2.27.0


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