Subject: [PATCH] coresight: tmc: change device registration from misc to cdev

From: Jay Chen <[email-masked]>
Date: Mon, 24 Jan 2022 19:00:18 +0800

Currently, there are 130 etr and etf on our machine,
but the current coresight tmc driver uses misc_register
to register the device, which leads to the error that
the device number is not enough.

coresight-tmc: probe of xxxxx failed with error -16

This patch changes the device registration method
to cdev's dynamic registration method to solve the
problem of insufficient device numbers.

Signed-off-by: Jay Chen <[email-masked]>
---
 .../hwtracing/coresight/coresight-tmc-core.c  | 103 ++++++++++++++----
 drivers/hwtracing/coresight/coresight-tmc.h   |  11 +-
 2 files changed, 91 insertions(+), 23 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
index d0276af82494..0977f1ce6338 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-core.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
@@ -12,7 +12,6 @@
 #include <linux/io.h>
 #include <linux/err.h>
 #include <linux/fs.h>
-#include <linux/miscdevice.h>
 #include <linux/mutex.h>
 #include <linux/property.h>
 #include <linux/uaccess.h>
@@ -31,6 +30,12 @@ DEFINE_CORESIGHT_DEVLIST(etb_devs, "tmc_etb");
 DEFINE_CORESIGHT_DEVLIST(etf_devs, "tmc_etf");
 DEFINE_CORESIGHT_DEVLIST(etr_devs, "tmc_etr");
 
+static DEFINE_IDA(tmc_ida);
+static dev_t tmc_major;
+static struct class *tmc_class;
+
+#define TMC_DEV_MAX	(MINORMASK + 1)
+
 void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata)
 {
 	struct coresight_device *csdev = drvdata->csdev;
@@ -146,8 +151,10 @@ static int tmc_read_unprepare(struct tmc_drvdata *drvdata)
 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_cdev *cdev = container_of(inode->i_cdev,
+					     struct tmc_cdev, cdev);
+	struct tmc_drvdata *drvdata = container_of(cdev,
+						   struct tmc_drvdata, cdev);
 
 	ret = tmc_read_prepare(drvdata);
 	if (ret)
@@ -178,8 +185,10 @@ 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_cdev *cdev = container_of(file->f_inode->i_cdev,
+					     struct tmc_cdev, cdev);
+	struct tmc_drvdata *drvdata = container_of(cdev,
+						   struct tmc_drvdata, cdev);
 	actual = tmc_get_sysfs_trace(drvdata, *ppos, len, &bufp);
 	if (actual <= 0)
 		return 0;
@@ -199,8 +208,10 @@ static ssize_t tmc_read(struct file *file, char __user *data, size_t len,
 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_cdev *cdev = container_of(inode->i_cdev,
+					     struct tmc_cdev, cdev);
+	struct tmc_drvdata *drvdata = container_of(cdev,
+						   struct tmc_drvdata, cdev);
 
 	ret = tmc_read_unprepare(drvdata);
 	if (ret)
@@ -451,6 +462,7 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 {
 	int ret = 0;
 	u32 devid;
+	dev_t devt;
 	void __iomem *base;
 	struct device *dev = &adev->dev;
 	struct coresight_platform_data *pdata = NULL;
@@ -546,14 +558,32 @@ 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 = ida_simple_get(&tmc_ida, 0, TMC_DEV_MAX, GFP_KERNEL);
+	if (ret < 0)
+		goto err_coresight_unregister;
+
+	cdev_init(&drvdata->cdev.cdev, &tmc_fops);
+	drvdata->cdev.cdev.owner = THIS_MODULE;
+	devt = MKDEV(MAJOR(tmc_major), ret);
+	ret = cdev_add(&drvdata->cdev.cdev, devt, 1);
 	if (ret)
-		coresight_unregister(drvdata->csdev);
-	else
+		goto err_free_tmc_ida;
+
+	drvdata->cdev.dev = device_create(tmc_class, NULL, devt, &drvdata->cdev, desc.name);
+	if (IS_ERR(drvdata->cdev.dev)) {
+		ret = PTR_ERR(drvdata->cdev.dev);
+		goto err_delete_cdev;
+	} else
 		pm_runtime_put(&adev->dev);
+
+	return 0;
+
+err_delete_cdev:
+	cdev_del(&drvdata->cdev.cdev);
+err_free_tmc_ida:
+	ida_simple_remove(&tmc_ida, MINOR(devt));
+err_coresight_unregister:
+	coresight_unregister(drvdata->csdev);
 out:
 	return ret;
 }
@@ -583,13 +613,11 @@ static void tmc_shutdown(struct amba_device *adev)
 static void tmc_remove(struct amba_device *adev)
 {
 	struct tmc_drvdata *drvdata = dev_get_drvdata(&adev->dev);
+	struct device *dev = drvdata->cdev.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);
+	ida_simple_remove(&tmc_ida, MINOR(dev->devt));
+	device_destroy(tmc_class, dev->devt);
+	cdev_del(&drvdata->cdev.cdev);
 	coresight_unregister(drvdata->csdev);
 }
 
@@ -618,7 +646,42 @@ static struct amba_driver tmc_driver = {
 	.id_table	= tmc_ids,
 };
 
-module_amba_driver(tmc_driver);
+static int __init tmc_init(void)
+{
+	int ret;
+
+	ret = alloc_chrdev_region(&tmc_major, 0, TMC_DEV_MAX, "tmc");
+	if (ret < 0) {
+		pr_err("tmc: failed to allocate char dev region\n");
+		return ret;
+	}
+
+	tmc_class = class_create(THIS_MODULE, "tmc");
+	if (IS_ERR(tmc_class)) {
+		pr_err("tmc: failed to create class\n");
+		unregister_chrdev_region(tmc_major, TMC_DEV_MAX);
+		return PTR_ERR(tmc_class);
+	}
+
+	ret = amba_driver_register(&tmc_driver);
+	if (ret) {
+		pr_err("tmc: error registering amba driver\n");
+		class_destroy(tmc_class);
+		unregister_chrdev_region(tmc_major, TMC_DEV_MAX);
+	}
+
+	return ret;
+}
+
+static void __exit tmc_exit(void)
+{
+	amba_driver_unregister(&tmc_driver);
+	class_destroy(tmc_class);
+	unregister_chrdev_region(tmc_major, TMC_DEV_MAX);
+}
+
+module_init(tmc_init);
+module_exit(tmc_exit);
 
 MODULE_AUTHOR("Pratik Patel <[email-masked]>");
 MODULE_DESCRIPTION("Arm CoreSight Trace Memory Controller driver");
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index 6bec20a392b3..11441c6b9c26 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -7,9 +7,9 @@
 #ifndef _CORESIGHT_TMC_H
 #define _CORESIGHT_TMC_H
 
+#include <linux/cdev.h>
 #include <linux/dma-mapping.h>
 #include <linux/idr.h>
-#include <linux/miscdevice.h>
 #include <linux/mutex.h>
 #include <linux/refcount.h>
 
@@ -163,11 +163,16 @@ struct etr_buf {
 	void				*private;
 };
 
+struct tmc_cdev {
+	struct cdev cdev;
+	struct device *dev;
+};
+
 /**
  * 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.
+ * @tmc_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.
@@ -191,7 +196,7 @@ struct etr_buf {
 struct tmc_drvdata {
 	void __iomem		*base;
 	struct coresight_device	*csdev;
-	struct miscdevice	miscdev;
+	struct tmc_cdev		cdev;
 	spinlock_t		spinlock;
 	pid_t			pid;
 	bool			reading;
-- 
2.27.0

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