Hi,
I have a question about the order in which devices are initialized.
The simpler case is this: A device X needs to be taken out of reset by
another device Y before it can be used.
To get this to work, one option is to modify the driver for Y to use
arch_initcall instead of device_initcall. This results in it being run
first, so that the other device X is out of reset by the time it is
initialized.
Is it possible within the devicetree to specify that one device must be
initialized before attempting to initialize another (to avoid needing to
modify the driver)?
A chicken-and-egg case: What if two devices use a common driver, but one
must first be used to bring the other out of reset? Eg: A GPIO expander
that is held in reset by another GPIO expander.
The goal would be to:
1. Initialize the first GPIO expander
2. Run a driver that takes the second expander out of reset using the
first
3. Initialize the second GPIO expander (which uses the same driver as
the first).
In this case, because the drivers for step 1 and step 3 are the same
driver, it is not possible to adjust the _initcall of the driver for
step 2 to be in-between them.
Is there a way to describe this situation in a devicetree such that the
driver for step 2 gets run in-between when the first and second GPIO
expanders are initialized?
Thank you,
Joshua
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