Re: [PATCH 2/2] gpiolib: Defer gpio device setup until after gpiolib initialization

Guenter Roeck
2016-04-01T03:31:18Z

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@uclinux.org>
>>>> Cc: Alexandre Courbot <gnurou@gmail.com>
>>>> Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
>>>> Signed-off-by: Guenter Roeck <linux@roeck-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;
>>>> }
>>>>
>>>
>>
>
>