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Date: Mon, 3 Jan 2022 11:28:48 -0700
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Jay Chen <jkchen@...ux.alibaba.com>
Cc: suzuki.poulose@....com, leo.yan@...aro.org,
alexander.shishkin@...ux.intel.com,
linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
linux-kernel@...r.kernel.org, zhangliguang@...ux.alibaba.com
Subject: Re: [RFC V3 PATCH] coresight: change tmc from misc device to cdev
device
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@...ux.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@...eaurora.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
>
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