Hello Heiko,
On 11/17/2016 09:08 AM, Heiko Schocher wrote:
Hello Guenter, Vladimir,
Sorry for the late response, but I was "on the road" ...
Am 15.11.2016 um 14:46 schrieb Guenter Roeck:
On 11/15/2016 03:32 AM, Vladimir Zapolskiy wrote:
On 11/15/2016 01:10 PM, Vladimir Zapolskiy wrote:
Hello Heiko,
On 11/15/2016 12:20 PM, Heiko Schocher wrote:
Hello,
commit e188cbf7564f: "gpio: mxc: shift gpio_mxc_init() to
subsys_initcall level"
moves the gpio initialization of the mxc gpio driver
from the arch_initcall level into subsys_initcall level.
This leads now on mxc boards, which use a gpio wdt driver
and the CONFIG_GPIO_WATCHDOG_ARCH_INITCALL option enabled,
to unwanted driver probe deferrals during kernel boot.
I see this currently on an imx6 based board (which has unfortunately
3 WDT: imx6 internal (disabled), gpio wdt and da9063 WDT ...).
Also a side effect from above commit is, that the da9063 WDT driver
is now probed before the gpio WDT driver ... so /dev/watchdog now
does not point to the gpio_wdt, instead it points to the da9063 WDT.
So there are 2 solutions possible:
- add a CONFIG_GPIO_MCX_ARCH_INITCALL option
in drivers/gpio/gpio-mxc.c like for the gpio_wdt.c driver?
in my opinion this is overly heavy solution and it might be
better to avoid it if possible.
I would rather prefer to reconsider GPIO_WATCHDOG_ARCH_INITCALL
usage in the watchdog driver.
Moreover adding this proposed GPIO_MCX_ARCH_INITCALL to call
the driver on arch level will result in deferring the GPIO driver.
But how can we guarantee, that first the gpio driver and then
the gpio_wdt driver gets probed?
- move the arch_initcall in gpio_wdt.c into a subsys_initcall
(Tested this, and the probe dereferral messages are gone ...)
But this may results in problems on boards, which needs an early
trigger on an gpio wdt ...
The level of "earliness" can not be defined in absolute time value
in any case, why decreasing the init level of the watchdog driver
to subsys level can cause problems? For that there should exist
some kind of a dependency on IC or PCB hardware level, can you
name it please?
On the current problem, there is no dependency on PCB, but I know
of watchdogs triggered through a gpio pin, which must triggered < 1 second
and subsys_initcall is too late for this. I think, this was the reason
This is not a valid reason, nobody guarantees that arch_initcall()
code is run in < 1 second time interval.
for introducing the CONFIG_GPIO_WATCHDOG_ARCH_INITCALL option ...
Putting GPIO driver on arch_initcall() level results in deferring
of the GPIO driver. Because you desire to avoid probe deferring, you
should not consider putting GPIO driver on arch_initcall() level.
--
With best wishes,
Vladimir
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