Date:	Thu, 31 Mar 2016 20:31:16 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Greg Ungerer <gregungerer@...tnet.com.au>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	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

On 03/31/2016 06:33 PM, Greg Ungerer wrote:
> On 01/04/16 10:53, Guenter Roeck wrote:
>> On Fri, Apr 01, 2016 at 10:29:11AM +1000, Greg Ungerer wrote:
>>> 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
>>
>> Probably coldfire ?
>>
>> arch/m68k/coldfire/gpio.c:
>
> Yes, that is the one.
>
>
>> static struct bus_type mcfgpio_subsys = {
>>          .name           = "gpio",
>> 	.dev_name       = "gpio",
>> };
>>
>> No idea what to do about that. Can that bus be renamed ?
>
> Yeah, it could. But is it even necessary at all now?
>
> I am thinking I could remove the subsys_system_register(&mcfgpio_subsys, NULL)
> call from that coldfire/gpio.c. Doing that certainly cleans up the
> boot. There was nothing much under the old coldfire /sys/gpio other than
> the standard devices/drivers/etc. And the new gpio api ofcourse has all
> that as well.
>
Sure, if that works for you.

Guenter

> Regards
> Greg
>
>
>>> The boot otherwise continues and is successful.
>>>
>> Thanks for testing!
>>
>> Guenter
>>
>>> 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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