Re: Pinmux driver model: per board vs. unified

Andre Guedes <andre.guedes@...>

Hi all,

Here is one proposal on how we can deal with pinmux drivers and board-
specific pinmux configurations:

1. All pinmux drivers land in driver/pinmux/ directory and they all
implement the include/pinmux.h API only.

2. Board-specific code (e.g. board/quark_d2000_crb/board.c) defines
the pinmux table and uses the pinmux APIs to apply its specific
configurations. To achieve that, we could define the board_init()
function in board.c which would handle any board-specific initialization,
including pinmux configuration. We could use SYS_INIT() so board_init()
is executed during kernel initialization.

In order to this approach work, we have to ensure the pinmux driver is
initialized before board_init() is called. This can be achieved by setting
pinmux driver initialization to PRIMARY level and board_init() to SECONDARY

AFAICS, this approach would work for all boards, besides Galileo. Pinmux
in Galileo is quite different and it would require a special handling.

Since Galileo pinmux driver depends on others devices (I2C, PCA9535 and
PCAL9685) we cannot init it on PRIMARY level. So the Galileo board_init()
would be set to SECONDARY level and we use the 'prio' argument from
SYS_INIT() to ensure board_init() is executed after galileo pinmux



Quoting Vinicius Costa Gomes (2016-02-23 15:18:25)

So I like the idea here to move all the code common to manipulating
the pinmux registers in to a single place.

The way this change goes about that is wrong IMHO. Each board should
have its own driver that uses the library code, not a single driver
that picks up the board specific code at link time. This forces the
user to look in their .config to figure out what board specific code
is included in their image.
Makes sense.

Where the library code lands is an open question ATM. This is very
similar to the QMSI stuff where we will be using a library for
accessing the registers in the IP block.
The only thing that may complicate matters a bit is the point that today
we have two ways of interacting with the pinmux registers, one that is
used by the board specific code and one that may be used by applications
(disabled by default).

Or do you mean we continue providing two pinmux APIs?

We need to figure out the correct long term model. This discussion
should happen on the mailing list instead of gerrit so all involved
can see whats going on.




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