Re: I2C and CAN bus on MPC5200B device tree

On 1/14/08, Wolfgang Grandegger [off-list ref] wrote:

Grant Likely wrote:

quoted

On 1/13/08, Matt Sealey [off-list ref] wrote:

quoted

Hi guys,

I know the I2C stuff is up in the air (I cannot pinpoint the documentation
for it) and have not found any CAN bus documentation for device trees.

I want to update the firmware tree to add these but, am basically looking
for those docs, or someone to go over a few points.. is there some kind of
tree standard I should be looking at, or some patch I missed which has
a driver which implements something that looks at a compatible tree?

I think some consensus has been achieved for describing i2c busses and
their attached devices, but I don't think booting-without-of.txt has
been updated with the details yet.  I need to look into that more.

I don't think anyone has tackled CAN.  Best bet is to draft a tree in
the way you think it should be described and post it to the list.
That will give a starting point for us to discuss it and come to
consensus.

For MSCAN on the MPC5200 we currently have:

                mscan@900 {
                        device_type = "mscan";
                        compatible = "mpc5200b-mscan","mpc5200-mscan";
                        cell-index = <0>;
                        interrupts = <2 11 0>;
                        interrupt-parent = <&mpc5200_pic>;
                        reg = <900 80>;
                };

                mscan@980 {
                        device_type = "mscan";
                        compatible = "mpc5200b-mscan","mpc5200-mscan";
                        cell-index = <1>;
                        interrupts = <2 12 0>;
                        interrupt-parent = <&mpc5200_pic>;
                        reg = <980 80>;
                };

The only thing missing is a property defining the routing of the CAN
signals, CAN 1 on I2C1 pins or CAN 2 on TMR01 pins. I think it does not
make sense to describe CAN devices on the CAN bus like for I2C.

I don't think that pin routing matters much for the device tree.
Ideally, firmware should be responsible for port_config, and as long
as it is already configured, the CAN device can find it's devices.

Cheers,
g.


-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.