[RFC V2 PATCH] coresight: change tmc from misc device to cdev device
Mathieu Poirier
mathieu.poirier at linaro.org
Fri Dec 17 09:18:59 PST 2021
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 at 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 at 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 at 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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