Message-ID: <0ce54a1d-294e-26da-27a9-14fb6eda0560@linux.alibaba.com>
Date:   Wed, 5 Jan 2022 10:16:31 +0800
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Subject: Re: [RFC V3 PATCH] coresight: change tmc from misc device to cdev
 device
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
Cc:     suzuki.poulose@arm.com, leo.yan@linaro.org,
        alexander.shishkin@linux.intel.com,
        linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org,
        linux-kernel@vger.kernel.org, zhangliguang@linux.alibaba.com
References: <20211221120437.4781-1-jkchen@linux.alibaba.com>
 <20220103182848.GA398730@p14s>
From:   Jiankang Chen <jkchen@linux.alibaba.com>
In-Reply-To: <20220103182848.GA398730@p14s>
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Hi Mathieu:

  I will resend the patch again

tks

jay

在 2022/1/4 02:28, Mathieu Poirier 写道:
> Good day Jay,
>
> For your next iteration, please remove the "RFC" from the patch title, we are
> well pass that now.
>
> On Tue, Dec 21, 2021 at 08:04:37PM +0800, Jay Chen wrote:
>> 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.
> This is much better.
>
>> Signed-off-by: Jay Chen <jkchen@linux.alibaba.com>
>> ---
>>   .../hwtracing/coresight/coresight-tmc-core.c  | 91 +++++++++++++++----
>>   drivers/hwtracing/coresight/coresight-tmc.h   | 10 +-
>>   2 files changed, 83 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> index d0276af82494..0d51071e9f88 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> @@ -31,6 +31,12 @@ 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;
>> @@ -147,7 +153,7 @@ 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 +185,7 @@ 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 +206,7 @@ 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)
>> @@ -451,6 +457,7 @@ 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 +553,32 @@ 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 +608,11 @@ 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, dev->devt);
> 	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 +641,43 @@ 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");
>> +		ret = PTR_ERR(tmc_class);
>> +		unregister_chrdev_region(tmc_major, TMC_DEV_MAX);
>> +		return ret;
> You can simply 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 <pratikp@codeaurora.org>");
>>   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..b65ac363f9e4 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc.h
>> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
>> @@ -7,6 +7,7 @@
>>   #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>
> miscdevice.h can likely be removed in both .c and .h files.
>
> Thanks,
> Mathieu
>
>> @@ -163,11 +164,16 @@ 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 +197,7 @@ 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
>>