Re: [RFC V2 PATCH] coresight: change tmc from misc device to cdev device

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Fri, Dec 17, 2021 at 03:54:27PM +0800, Leo Yan wrote:
> Hi Jay,
> 
> On Fri, Dec 17, 2021 at 11:42:08AM +0800, Jay Chen wrote:
> > From: root <root@localhost.localdomain>
> 
> Please use your company's email address rather than using an invalid
> email address.
> 
> > For coresight in the server scenario, if there are too many
> > funnel (about 130) and tmc (about 130) peripherals, the error
> > of insufficient device numbers will occur by misc device
> 
> Incomplete commit log ...
> 
> For a better practice, it's deserve to write a high quality commit log
> which is helpful for maintainers to understand your patch, at the end,
> it also can accelerate your patch's merging.  Let me quote a suggestion
> for the commit log format from an old reply [1]:
> 
> ... Please use the customary changelog style we use in the kernel:
> 
>   " Current code does (A), this has a problem when (B).
>     We can improve this doing (C), because (D)."
> 
> [1] https://lkml.org/lkml/2013/11/11/146
> 
> > Signed-off-by: root <root@localhost.localdomain>
> 
> > ---
> >  .../hwtracing/coresight/coresight-tmc-core.c  | 84 +++++++++++++++----
> >  drivers/hwtracing/coresight/coresight-tmc.h   | 10 ++-
> >  2 files changed, 75 insertions(+), 19 deletions(-)
> > 
> > diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
> > index d0276af82494..03b114c0616a 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
> > @@ -31,6 +31,11 @@ DEFINE_CORESIGHT_DEVLIST(etb_devs, "tmc_etb");
> >  DEFINE_CORESIGHT_DEVLIST(etf_devs, "tmc_etf");
> >  DEFINE_CORESIGHT_DEVLIST(etr_devs, "tmc_etr");
> >  
> > +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 +152,7 @@ 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 +184,7 @@ 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 +205,7 @@ 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)
> > @@ -449,8 +454,9 @@ static u32 tmc_etr_get_max_burst_size(struct device *dev)
> >  
> >  static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
> >  {
> > -	int ret = 0;
> > +	int ret = 0, tmc_num = 0;
> >  	u32 devid;
> > +	dev_t devt;
> >  	void __iomem *base;
> >  	struct device *dev = &adev->dev;
> >  	struct coresight_platform_data *pdata = NULL;
> > @@ -546,14 +552,26 @@ 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);
> > -	if (ret)
> > +	tmc_num = etb_devs.nr_idx + etf_devs.nr_idx +
> > +			  etr_devs.nr_idx;
> 
> I am struggling to understand this line code, but looks to me this is
> right.  The system might have both ETR and ETF components, so we
> need to calculate index for all sinks.
> 
> > +
> > +	cdev_init(&drvdata->cdev.cdev, &tmc_fops);
> > +	drvdata->cdev.cdev.owner = THIS_MODULE;
> > +	devt = MKDEV(MAJOR(tmc_major), tmc_num - 1);
> > +	ret = cdev_add(&drvdata->cdev.cdev, devt, 1);
> > +	if (ret) {
> >  		coresight_unregister(drvdata->csdev);
> > -	else
> > +		goto out;
> > +	}
> > +
> > +	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);
> > +		cdev_del(&drvdata->cdev.cdev);
> > +		coresight_unregister(drvdata->csdev);
> > +	} else
> >  		pm_runtime_put(&adev->dev);
> > +
> >  out:
> >  	return ret;
> >  }
> > @@ -584,12 +602,8 @@ static void 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);
> > +	device_destroy(tmc_class, drvdata->cdev.dev->devt);
> > +	cdev_del(&drvdata->cdev.cdev);
> >  	coresight_unregister(drvdata->csdev);
> >  }
> >  
> > @@ -618,7 +632,43 @@ 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("failed to create tmc class\n");
> > +		ret = PTR_ERR(tmc_class);
> > +		unregister_chrdev_region(tmc_major, TMC_DEV_MAX);
> > +		return ret;
> > +	}
> > +
> > +	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);
> 
> Should invoke tmc_init() in an ealier phase so it can prepare device class
> prior to the TMC devices registration?  In other words, I think here
> should be:
> 
>   subsys_initcall(tmc_init);

TMC devices won't be registered until a TMC driver is registered, which happens
after the creation of the class.  Anything I am missing?

> 
> Thanks,
> Leo
> 
> > +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>
> > @@ -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
> > 

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