QUERY: How to handle SOC Configuration (Peripheral Multiplexing) in linux

[jassi brar]

On Mon, Mar 15, 2010 at 2:14 PM, Shiraz HASHIM <shiraz.hashim at st.com> wrote:
> Hello Jassi,
>
> On 3/15/2010 10:17 AM, jassi brar wrote:
>> On Mon, Mar 15, 2010 at 1:31 PM, Viresh KUMAR <viresh.kumar at st.com> wrote:
>>> In our SOC's (SPEArxxx), we have many peripheral sharing PL_GPIO pins and so
>>> only few peripherals can be selected in a configuration. This is configurable
>>> using a set of registers. Now the problem is to make following work:
>>>
>>> 1. How to do this selection in kernel in a simple way?
>>> 2. Based on this selection hardware registers needs to be configured.
>> Why can't you make the drivers acquire and setup the necessary pins during
>> probe?
>> Among other benefits, it enables you to use the same kernel image and device
>> drivers as modules -- if a GPIO can be used by two different device
>> controllers, you
>> can switch the 'mode' of the board by simple rmmod-insmod
>
> I think the problem is we cannot change the standard drivers (already in the
> mainline). So if the standard driver doesn't support this in its probe, then
> how should we manage this?
Though the drivers should already have done that, but still you can always
submit patches to improve.

> Further these configurations are board dependent, so I think driver must be
> independent of this.
Don't really understand this. Viresh said that the SoC can configure GPIOs for
a controller or the other, which is quite common and is handled during probe.
Also, it's desirable to have one kernel image run on many machines with the
same SOC.