2016-07-25 16:15 GMT+02:00 Thierry Reding [off-list ref]:

On Mon, Jul 25, 2016 at 03:16:28PM +0200, Mirza Krak wrote:

quoted

2016-07-25 13:30 GMT+02:00 Thierry Reding [off-list ref]:

quoted

I would've expected this to require some sort of infrastructure to allow
devices connected to the GMI controller to acquire the bus via some API
to select their chip.

Yes, ultimately you would need some sort of infrastructure to allow
devices to acquire the GMI bus if you want to solve this in software.
But at the moment I do not see such an infrastructure in place, and is
it feasible to add one specifically for the GMI controller? If one
such infrastructure was in place we would need to modify all the
drivers that want to use to include Tegra specific infrastructure to
access the GMI bus?

Since my knowledge is limited it hard for me to comment on this, maybe
there is a simple way of doing this?

I don't think there's a simple way to do this. In order to properly
implement it we'd need to implement a generic infrastructure for chip
selects so that drivers such as the one for your CAN controller can be
written without tying them specifically to the Tegra GMI controller.

From what you and Jon were saying it sounds like the drivers are
completely agnostic of any chip-select, so conversion won't be easy.
But technically if these chips take a chip-select as input then it's
always possible to hook them up to a controller that doesn't do this
automatic translation of address to chip-select, so eventually some
setup is bound to come along where they'd need explicit chip-select
handling as well.

I don't think it's fair to require you to implement this infrastructure
if you don't actually need it. At the same time I want to be cautious
and make sure we keep the driver and binding flexible enough to allow
us to implement explicit chip-selects should we later need them.

Thierry

One thing that should be noted, and that is the GMI controller also
supports a DMA master mode (feature for the future?).

I do not really know how this effects the binding we are discussing
but wanted to put it out there.

Best Regards,
Mirza