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

From: Mathieu Poirier <[email-masked]>
Date: Tue, 25 Jan 2022 09:46:25 -0700

On Tue, Jan 25, 2022 at 10:33:45AM +0800, Jiankang Chen wrote:
> Hi Mathieu
> 
> 在 2022/1/25 04:08, Mathieu Poirier 写道:
> > On Mon, 24 Jan 2022 at 04:00, Jay Chen <[email-masked]> 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 patch is still not labelled properly and as such being dropped.
> 
> Hello, about the label of this patch, what kind of patch should I add?
>

So far you've sent 6 different version of this patch...  Wouldn't it make sense
to label this one "PATCH v7" ?

Leo has pointed out a good presentation from Marc Zingier - I also suggest you
invest time reading it.

> Thanks very much
> 
> jay
> 
> > > 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
> > > 

_______________________________________________
linux-arm-kernel mailing list
[email-masked]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel