Date:	Fri, 1 Apr 2016 10:29:11 +1000
From:	Greg Ungerer <gregungerer@...tnet.com.au>
To:	Guenter Roeck <linux@...ck-us.net>,
	Linus Walleij <linus.walleij@...aro.org>
Cc:	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alexandre Courbot <gnurou@...il.com>,
	Greg Ungerer <gerg@...inux.org>
Subject: Re: [PATCH 2/2] gpiolib: Defer gpio device setup until after gpiolib
 initialization

Hi Guenter,

On 01/04/16 01:11, Guenter Roeck wrote:
> Since commit ff2b13592299 ("gpio: make the gpiochip a real device"),
> attempts to add a gpio chip prior to gpiolib initialization cause
> the system to crash. This happens because gpio_bus_type has not been
> registered yet. Defer creating gpio devices until after gpiolib has
> been initialized to fix the problem.
> 
> Cc: Greg Ungerer <gerg@...inux.org>
> Cc: Alexandre Courbot <gnurou@...il.com>
> Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

Thanks for putting these patches together.
I can now boot all my boards again with them applied :-)

But, I am seeing an issue on one of my targets during boot:

...
Mount-cache hash table entries: 2048 (order: 0, 8192 bytes)
Mountpoint-cache hash table entries: 2048 (order: 0, 8192 bytes)
clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at fs/sysfs/dir.c:31 0x000da0e6
sysfs: cannot create duplicate filename '/bus/gpio'
Modules linked in:
CPU: 0 PID: 1 Comm: swapper Not tainted 4.6.0-rc1-dirty #1
Stack from 0383de38:
        0383de38 0021f692 00027eb0 03841000 002134f2 038261b0 0382f688 00111c1e
        00027efe 0021ccc4 0000001f 000da0e6 00000009 00000000 0383de74 0021cc91
        0383de90 0383df8c 000da0e6 0021ccc4 0000001f 0021cc91 03841000 002134f2
        038261b0 0382f688 00000000 000da1f0 038261b0 002134f2 0382f688 0382f688
        00111d86 0382f688 00000000 0382f688 0382f688 0382f680 0024fe84 0002118e
        0383df8c 0382f688 00112094 0382f688 00000000 0013f5dc 0382f680 00000001
Call Trace:
 ...
---[ end trace 013025e2024d8831 ]---
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at lib/kobject.c:240 0x00111fc0
kobject_add_internal failed for gpio with -EEXIST, don't try to register things with the same name in the same directory.
Modules linked in:
CPU: 0 PID: 1 Comm: swapper Tainted: G        W       4.6.0-rc1-dirty #1
Stack from 0383de68:
        0383de68 0021f692 00027eb0 ffffffef 0382f688 00000000 0382f688 00111a26
        00027efe 0021f817 000000f0 00111fc0 00000009 00000000 0383dea4 0021f8cd
        0383dec0 0383df8c 00111fc0 0021f817 000000f0 0021f8cd 002069e9 002134f2
        0382f688 0382f680 0024fe84 0002118e 0383df8c 0382f688 00112094 0382f688
        00000000 0013f5dc 0382f680 00000001 0000001f 002600de 00265950 0002118e
        0383df8c 002600f2 0024fe84 00000001 002600de 00265950 0002118e 00021274
Call Trace:
...
---[ end trace 013025e2024d8832 ]---
gpiolib: could not register GPIO bus type
NET: Registered protocol family 16
...

The boot otherwise continues and is successful.

Regards
Greg


> ---
>  drivers/gpio/gpiolib.c | 98 ++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 67 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index f1531070814d..8bb24dc8dc3d 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -68,6 +68,7 @@ LIST_HEAD(gpio_devices);
>  static void gpiochip_free_hogs(struct gpio_chip *chip);
>  static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
>  
> +static bool gpiolib_initialized;
>  
>  static inline void desc_set_label(struct gpio_desc *d, const char *label)
>  {
> @@ -445,6 +446,58 @@ static void gpiodevice_release(struct device *dev)
>  	kfree(gdev);
>  }
>  
> +static int gpiochip_setup_dev(struct gpio_device *gdev)
> +{
> +	int status;
> +
> +	cdev_init(&gdev->chrdev, &gpio_fileops);
> +	gdev->chrdev.owner = THIS_MODULE;
> +	gdev->chrdev.kobj.parent = &gdev->dev.kobj;
> +	gdev->dev.devt = MKDEV(MAJOR(gpio_devt), gdev->id);
> +	status = cdev_add(&gdev->chrdev, gdev->dev.devt, 1);
> +	if (status < 0)
> +		chip_warn(gdev->chip, "failed to add char device %d:%d\n",
> +			  MAJOR(gpio_devt), gdev->id);
> +	else
> +		chip_dbg(gdev->chip, "added GPIO chardev (%d:%d)\n",
> +			 MAJOR(gpio_devt), gdev->id);
> +	status = device_add(&gdev->dev);
> +	if (status)
> +		goto err_remove_chardev;
> +
> +	status = gpiochip_sysfs_register(gdev);
> +	if (status)
> +		goto err_remove_device;
> +
> +	/* From this point, the .release() function cleans up gpio_device */
> +	gdev->dev.release = gpiodevice_release;
> +	get_device(&gdev->dev);
> +	pr_debug("%s: registered GPIOs %d to %d on device: %s (%s)\n",
> +		 __func__, gdev->base, gdev->base + gdev->ngpio - 1,
> +		 dev_name(&gdev->dev), gdev->chip->label ? : "generic");
> +
> +	return 0;
> +
> +err_remove_device:
> +	device_del(&gdev->dev);
> +err_remove_chardev:
> +	cdev_del(&gdev->chrdev);
> +	return status;
> +}
> +
> +static void gpiochip_setup_devs(void)
> +{
> +	struct gpio_device *gdev;
> +	int err;
> +
> +	list_for_each_entry(gdev, &gpio_devices, list) {
> +		err = gpiochip_setup_dev(gdev);
> +		if (err)
> +			pr_err("%s: Failed to initialize gpio device (%d)\n",
> +			       dev_name(&gdev->dev), err);
> +	}
> +}
> +
>  /**
>   * gpiochip_add_data() - register a gpio_chip
>   * @chip: the chip to register, with chip->base initialized
> @@ -459,6 +512,9 @@ static void gpiodevice_release(struct device *dev)
>   * the gpio framework's arch_initcall().  Otherwise sysfs initialization
>   * for GPIOs will fail rudely.
>   *
> + * gpiochip_add_data() must only be called after gpiolib initialization,
> + * ie after core_initcall().
> + *
>   * If chip->base is negative, this requests dynamic assignment of
>   * a range of valid GPIOs.
>   */
> @@ -515,7 +571,7 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
>  	if (chip->ngpio == 0) {
>  		chip_err(chip, "tried to insert a GPIO chip with zero lines\n");
>  		status = -EINVAL;
> -		goto err_free_gdev;
> +		goto err_free_descs;
>  	}
>  
>  	if (chip->label)
> @@ -597,39 +653,16 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
>  	 * we get a device node entry in sysfs under
>  	 * /sys/bus/gpio/devices/gpiochipN/dev that can be used for
>  	 * coldplug of device nodes and other udev business.
> +	 * We can do this only if gpiolib has been initialized.
> +	 * Otherwise, defer until later.
>  	 */
> -	cdev_init(&gdev->chrdev, &gpio_fileops);
> -	gdev->chrdev.owner = THIS_MODULE;
> -	gdev->chrdev.kobj.parent = &gdev->dev.kobj;
> -	gdev->dev.devt = MKDEV(MAJOR(gpio_devt), gdev->id);
> -	status = cdev_add(&gdev->chrdev, gdev->dev.devt, 1);
> -	if (status < 0)
> -		chip_warn(chip, "failed to add char device %d:%d\n",
> -			  MAJOR(gpio_devt), gdev->id);
> -	else
> -		chip_dbg(chip, "added GPIO chardev (%d:%d)\n",
> -			 MAJOR(gpio_devt), gdev->id);
> -	status = device_add(&gdev->dev);
> -	if (status)
> -		goto err_remove_chardev;
> -
> -	status = gpiochip_sysfs_register(gdev);
> -	if (status)
> -		goto err_remove_device;
> -
> -	/* From this point, the .release() function cleans up gpio_device */
> -	gdev->dev.release = gpiodevice_release;
> -	get_device(&gdev->dev);
> -	pr_debug("%s: registered GPIOs %d to %d on device: %s (%s)\n",
> -		 __func__, gdev->base, gdev->base + gdev->ngpio - 1,
> -		 dev_name(&gdev->dev), chip->label ? : "generic");
> -
> +	if (gpiolib_initialized) {
> +		status = gpiochip_setup_dev(gdev);
> +		if (status)
> +			goto err_remove_chip;
> +	}
>  	return 0;
>  
> -err_remove_device:
> -	device_del(&gdev->dev);
> -err_remove_chardev:
> -	cdev_del(&gdev->chrdev);
>  err_remove_chip:
>  	acpi_gpiochip_remove(chip);
>  	gpiochip_free_hogs(chip);
> @@ -2834,6 +2867,9 @@ static int __init gpiolib_dev_init(void)
>  	if (ret < 0) {
>  		pr_err("gpiolib: failed to allocate char dev region\n");
>  		bus_unregister(&gpio_bus_type);
> +	} else {
> +		gpiolib_initialized = true;
> +		gpiochip_setup_devs();
>  	}
>  	return ret;
>  }
> 

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