Hi Alexandre,
On 31/03/16 15:59, 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.
Thanks for letting me know. I wasn't going to rush any fixes,
happy to let Linus decide how to handle it.
Regards
Greg
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