[PATCH v2] pinctrl: queue GPIO operations instead of defering
Stephen Warren
swarren at wwwdotorg.org
Mon Aug 19 15:15:42 EDT 2013
On 08/17/2013 08:56 AM, Linus Walleij wrote:
> We currently defer probing of the caller if a pinctrl GPIO
> request or direction setting comes in before the range mapping
> a certain GPIO to a certain pin controller is available.
>
> This can end up with a circular dependency: the GPIO driver
> needs the pin controller to be ready
So that much is explained above; it's because some GPIO APIs call into
pinctrl to manage GPIO-vs-pinmux-function setup.
> and the pin controller need the GPIO driver to be ready.
Why does that happen?
> This also happens if
> pin controllers and GPIO controllers compiled as modules
> are inserted in a certain order.
Shouldn't deferred probe resolve that just fine, assuming there are no
circular dependencies? In other words, this is just a special case of
the explanation above, so probably not worth explicitly mentioning.
...
> On the Nomadik we get this situation with the pinctrl
> driver when moving to requesting GPIOs off the gpiochip
> right after it has been added,
So, the pinctrl driver calls gpio_request()? Surely the solution is
simply not to do that?
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