Using the gpio i2c multiplexer driver

Using the gpio i2c multiplexer driver

[Guenter Roeck]

Hi all,

I am trying to use the new GPIO based I2C multiplexer. Unfortunately, I
have an initialization problem with it.

Some time after registering the multiplexer as platform driver, its
probe function is called. Unfortunately, that does not happen in sync
with I2C adapter initialization. The GPIO mux probe function is called
before the parent's (ie the multiplexed I2C adapter) probe function is
called. As a result, the GPIO mux driver does not find its parent i2c
adapter, and the probe function aborts with an error.

Any idea how I I can fix the problem, ie how I can ensure that the GPIO
mux probe function is only called after its parent I2C adapter is
initialized ?

Thanks,
Guenter

Re: Using the gpio i2c multiplexer driver

[Michael Lawnick]

Guenter Roeck said the following:
> Hi all,
> 
> I am trying to use the new GPIO based I2C multiplexer. Unfortunately, I
> have an initialization problem with it.
> 
> Some time after registering the multiplexer as platform driver, its
> probe function is called. Unfortunately, that does not happen in sync
> with I2C adapter initialization. The GPIO mux probe function is called
> before the parent's (ie the multiplexed I2C adapter) probe function is
> called. As a result, the GPIO mux driver does not find its parent i2c
> adapter, and the probe function aborts with an error.
> 
> Any idea how I I can fix the problem, ie how I can ensure that the GPIO
> mux probe function is only called after its parent I2C adapter is
> initialized ?
> 
Well, I assume your GPIO-Mux is registered as an GPIO device? Can't you
add it as an I2C-device? This way the right sequence should be kept.

HTH
-- 
Michael

Re: Using the gpio i2c multiplexer driver

[Guenter Roeck]

On Wed, Feb 16, 2011 at 02:07:26AM -0500, Michael Lawnick wrote:
> Guenter Roeck said the following:
> > Hi all,
> > 
> > I am trying to use the new GPIO based I2C multiplexer. Unfortunately, I
> > have an initialization problem with it.
> > 
> > Some time after registering the multiplexer as platform driver, its
> > probe function is called. Unfortunately, that does not happen in sync
> > with I2C adapter initialization. The GPIO mux probe function is called
> > before the parent's (ie the multiplexed I2C adapter) probe function is
> > called. As a result, the GPIO mux driver does not find its parent i2c
> > adapter, and the probe function aborts with an error.
> > 
> > Any idea how I I can fix the problem, ie how I can ensure that the GPIO
> > mux probe function is only called after its parent I2C adapter is
> > initialized ?
> > 
> Well, I assume your GPIO-Mux is registered as an GPIO device? Can't you
> add it as an I2C-device? This way the right sequence should be kept.
> 
It is registered as a platform device. I thought about registering it as 
I2C device, but it is not an I2C device itself, so that would be a bit kludgy.

Thanks,
Guenter

Re: Using the gpio i2c multiplexer driver

[Peter Korsgaard]

>>>>> "Guenter" == Guenter Roeck <guenter.roeck-IzeFyvvaP7pWk0Htik3J/w@public.gmane.org> writes:

 Guenter> Hi all,

 Guenter> I am trying to use the new GPIO based I2C
 Guenter> multiplexer. Unfortunately, I have an initialization problem
 Guenter> with it.

 Guenter> Some time after registering the multiplexer as platform driver, its
 Guenter> probe function is called. Unfortunately, that does not happen in sync
 Guenter> with I2C adapter initialization. The GPIO mux probe function is called
 Guenter> before the parent's (ie the multiplexed I2C adapter) probe function is
 Guenter> called. As a result, the GPIO mux driver does not find its parent i2c
 Guenter> adapter, and the probe function aborts with an error.

 Guenter> Any idea how I I can fix the problem, ie how I can ensure that
 Guenter> the GPIO mux probe function is only called after its parent
 Guenter> I2C adapter is initialized ?

What i2c bus controller are you using? Are you registering it's platform
data very late (E.G. after you register the platform data for gpiomux)?

If you do register the platform data in the correct order, things SHOULD
work correctly as busses are listed in drivers/i2c/Makefile before
muxes, but alternatively you could play with the init order (E.G. use
subsys_initcall instead of module_init in the bus driver, see
b8680784875 for an example).

-- 
Bye, Peter Korsgaard

Re: Using the gpio i2c multiplexer driver

[Guenter Roeck]

Peter,

On Wed, Feb 16, 2011 at 03:13:07AM -0500, Peter Korsgaard wrote:
> >>>>> "Guenter" == Guenter Roeck <guenter.roeck-IzeFyvvaP7pWk0Htik3J/w@public.gmane.org> writes:
> 
>  Guenter> Hi all,
> 
>  Guenter> I am trying to use the new GPIO based I2C
>  Guenter> multiplexer. Unfortunately, I have an initialization problem
>  Guenter> with it.
> 
>  Guenter> Some time after registering the multiplexer as platform driver, its
>  Guenter> probe function is called. Unfortunately, that does not happen in sync
>  Guenter> with I2C adapter initialization. The GPIO mux probe function is called
>  Guenter> before the parent's (ie the multiplexed I2C adapter) probe function is
>  Guenter> called. As a result, the GPIO mux driver does not find its parent i2c
>  Guenter> adapter, and the probe function aborts with an error.
> 
>  Guenter> Any idea how I I can fix the problem, ie how I can ensure that
>  Guenter> the GPIO mux probe function is only called after its parent
>  Guenter> I2C adapter is initialized ?
> 
> What i2c bus controller are you using? Are you registering it's platform
> data very late (E.G. after you register the platform data for gpiomux)?
> 
It is part of an mfd device. The same device also hosts the multiplexer pin.
The bus drivers and the multiplexer driver are instantiated from the mfd core
driver, so I can control the order.

> If you do register the platform data in the correct order, things SHOULD

The I2C bus driver is registered before the GPIO driver.

> work correctly as busses are listed in drivers/i2c/Makefile before
> muxes, but alternatively you could play with the init order (E.G. use
> subsys_initcall instead of module_init in the bus driver, see
> b8680784875 for an example).
> 

I tried that, but it does not help.

Here is a log:

[   16.027528] spanky_i2c spanky_i2c.12: probe 12
[   16.130652] spanky_i2c spanky_i2c.13: probe 13
[   16.131095] spanky-i2cmux spanky-i2cmux.72: Parent adapter (54) not found
		^^^ This is the (renamed) gpio mux driver
[   16.284040] spanky_i2c spanky_i2c.14: probe 14
[   16.292194] spanky_i2c spanky_i2c.15: probe 15
[   16.300029] spanky_i2c spanky_i2c.18: probe 18
[   16.394173] spanky_i2c spanky_i2c.19: probe 19
[   16.537542] spanky_i2c spanky_i2c.20: probe 20
[   16.544743] spanky_i2c spanky_i2c.21: probe 21
[   16.552497] spanky_i2c spanky_i2c.24: probe 24
[   16.657112] spanky_i2c spanky_i2c.25: probe 25
[   16.806678] spanky_i2c spanky_i2c.26: probe 26
[   16.815207] spanky_i2c spanky_i2c.27: probe 27
[   17.396906] spanky_i2c spanky_i2c.30: probe 30
[   17.500035] spanky_i2c spanky_i2c.31: probe 31
[   17.652316] spanky_i2c spanky_i2c.32: probe 32
[   17.659550] spanky_i2c spanky_i2c.33: probe 33
[   18.137137] spanky_i2c spanky_i2c.36: probe 36
[   18.239038] spanky_i2c spanky_i2c.37: probe 37
[   18.390166] spanky_i2c spanky_i2c.38: probe 38
[   18.400315] spanky_i2c spanky_i2c.39: probe 39
[   18.857240] spanky_i2c spanky_i2c.42: probe 42
[   18.961723] spanky_i2c spanky_i2c.43: probe 43
[   19.117111] spanky_i2c spanky_i2c.44: probe 44
[   19.125823] spanky_i2c spanky_i2c.45: probe 45
[   19.746365] spanky_i2c spanky_i2c.54: probe 54
		^^^ this is where the i2c bus driver is registered
[   19.758068] spanky_i2c spanky_i2c.55: probe 55
[   19.768026] spanky_i2c spanky_i2c.55: Registering I2C device pca9541 at 0x74
[   19.768378] spanky_i2c spanky_i2c.55: Registering I2C device pca9541 at 0x75
[   19.768729] spanky_i2c spanky_i2c.56: probe 56
[   19.778987] spanky_i2c spanky_i2c.57: probe 57
[   19.789395] spanky_i2c spanky_i2c.57: Registering I2C device pca9541 at 0x70
[   19.789741] spanky_i2c spanky_i2c.58: probe 58

As you can see, I have a somewhat special situation, with a large number
of I2C bus driver instances. It would work if there was only one instance,
but that does not help me.

I thought about registering the GPIO driver as I2C device as suggested
in the other response, but that would be a bit kludgy and I would prefer 
to avoid it if I can.

Thanks,
Guenter

Re: Using the gpio i2c multiplexer driver

[Guenter Roeck]

On Wed, Feb 16, 2011 at 03:13:07AM -0500, Peter Korsgaard wrote:
> >>>>> "Guenter" == Guenter Roeck <guenter.roeck-IzeFyvvaP7pWk0Htik3J/w@public.gmane.org> writes:
> 
>  Guenter> Hi all,
> 
>  Guenter> I am trying to use the new GPIO based I2C
>  Guenter> multiplexer. Unfortunately, I have an initialization problem
>  Guenter> with it.
> 
>  Guenter> Some time after registering the multiplexer as platform driver, its
>  Guenter> probe function is called. Unfortunately, that does not happen in sync
>  Guenter> with I2C adapter initialization. The GPIO mux probe function is called
>  Guenter> before the parent's (ie the multiplexed I2C adapter) probe function is
>  Guenter> called. As a result, the GPIO mux driver does not find its parent i2c
>  Guenter> adapter, and the probe function aborts with an error.
> 
>  Guenter> Any idea how I I can fix the problem, ie how I can ensure that
>  Guenter> the GPIO mux probe function is only called after its parent
>  Guenter> I2C adapter is initialized ?
> 
> What i2c bus controller are you using? Are you registering it's platform
> data very late (E.G. after you register the platform data for gpiomux)?
> 
> If you do register the platform data in the correct order, things SHOULD
> work correctly as busses are listed in drivers/i2c/Makefile before
> muxes, but alternatively you could play with the init order (E.G. use
> subsys_initcall instead of module_init in the bus driver, see
> b8680784875 for an example).
> 
Turns out
	 bus_register_notifier(&i2c_bus_type, &my_bus_notifier);
is my friend here.

Wait for the i2c adapter to be registered, which results in a notifier call.
Then register the mux driver from the notifier function.

Guenter