On 03/30/2016 10:59 PM, Alexandre Courbot wrote:
On Wed, Mar 30, 2016 at 10:49 AM, Greg Ungerer <gerg@xxxxxxxxxxx> wrote:
Hi Linus,
Commit 3c702e99 ("gpio: add a userspace chardev ABI for GPIOs")
breaks booting on all my m68k/ColdFire platforms (with MMU and
without). They all hang during the boot up, the last console
trace is:
...
NR_IRQS:256
clocksource: pit: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1467848399018 ns
Calibrating delay loop... 1042.02 BogoMIPS (lpj=5210112)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 2048 (order: 0, 8192 bytes)
Mountpoint-cache hash table entries: 2048 (order: 0, 8192 bytes)
I traced this back to gpiochip_add_data() when it does the
device_add() call. On my platforms this is being called
before gpiolib_dev_init(), and this seems to be the issue.
So gpio_bus_type has not been registered as a bus yet.
The lowest level ColdFire gpio code (arch/m68k/coldfire/gpio.c)
calls its setup from core_initcall() - and this will call
gpiochip_add_data(). This is being called first, before
the core_initcall() for gpiolib_dev_init().
We got a similar report with an alternative workaround:
https://lkml.org/lkml/2016/3/29/714
I can fix by changing the core_initcall() in coldfire/gpio.c
to something like postcore_initcall() and that fixes the boot
problem.
What do you think?
Would you expect that all callers of gpiochip_add_data()
should be after core_initcall()?
As you can see on the discussion thread above, there are several
candidate fixes - I have been away from GPIO for too long to make a
good decision, but I'm sure Linus can make the call.
I've started looking into a clean solution, as you had suggested
in the other thread. It will take a while, though. For the time being,
and/or unless someone else steps in who knows gpio much better than
I do, I think some workarund like my proposed hack should get
committed into the branch.
Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
