Hi Stephen,
On 13 May 2014 09:30, Stephen Warren swarren@wwwdotorg.org wrote:
On 05/09/2014 11:28 AM, Simon Glass wrote:
This is an implementation of GPIOs for Tegra that uses driver model. It has been tested on trimslice and also using the new iotrace feature.
The implementation uses a top-level GPIO device (which has no actual GPIOS). Under this all the banks are created as separate GPIO devices.
I still believe that there is a single Tegra GPIO controller, and this should be represented by a single device in the U-Boot device model.
It is possible that this is the best way to go, but it is far from certain. I have just had a try at implementing this for exynos now that the GPIO patches have been applied. I find a number of independent GPIO banks which fits nicely into the driver model idea of hierarchical devices. I'm on the fence with Tegra, but feel my approach is reasonable for now.
If we go with the route you suggest, we'll have to deal with a single device having multiple banks. That may be necessary/expedient at some point but for now I would prefer to add complexity/features as they are needed, and not before. Once we have a few more GPIO conversions done it should be clearer. It is very early days with driver model and we don't have a lot of information as to what is best. If we want to change the way GPIO drivers are done in a few months, it is not a big job and I will happily do it, I just don't want to build more complexity than we need early on.
There is also no need for a single hardware device to be a single U-Boot 'struct device'. In particular mfd devices have several children with different functions. One of the founding principles of U-Boot's driver model was to support child devices easily and in a general way. IMO we might as well take advantage of it.
Regards, Simon