I2C and CAN bus on MPC5200B device tree

I2C and CAN bus on MPC5200B device tree

[Matt Sealey]

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?

-- 
Matt Sealey <matt@genesi-usa.com>
Genesi, Manager, Developer Relations

Re: I2C and CAN bus on MPC5200B device tree

[Grant Likely]

On 1/13/08, Matt Sealey <matt@genesi-usa.com> wrote:
>
> 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.

Cheers,
g.

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

Re: I2C and CAN bus on MPC5200B device tree

[Olof Johansson]

On Sun, Jan 13, 2008 at 05:35:09PM -0700, Grant Likely wrote:
> On 1/13/08, Matt Sealey <matt@genesi-usa.com> wrote:
> >
> > 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 think simple devices might have been agreed upon (but it's been a
while since it was covered). Muxed busses probably hasn't. Either that
or I completely missed the emails.


-Olof

Re: I2C and CAN bus on MPC5200B device tree

[Wolfgang Grandegger]

Grant Likely wrote:
> On 1/13/08, Matt Sealey <matt@genesi-usa.com> wrote:
>> 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.

Wolfgang.

Re: I2C and CAN bus on MPC5200B device tree

[Grant Likely]

On 1/14/08, Wolfgang Grandegger <wg@grandegger.com> wrote:
> Grant Likely wrote:
> > On 1/13/08, Matt Sealey <matt@genesi-usa.com> wrote:
> >> 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.

Re: I2C and CAN bus on MPC5200B device tree

[Scott Wood]

On Sun, Jan 13, 2008 at 10:42:16PM -0600, Olof Johansson wrote:
> I think simple devices might have been agreed upon (but it's been a
> while since it was covered). Muxed busses probably hasn't. Either that
> or I completely missed the emails.

I posted something in one of the i2c device tree threads a while ago:
http://ozlabs.org/pipermail/linuxppc-dev/2007-May/036353.html

Basically, you just have a node that is both an i2c device and an i2c
controller, and the mux driver binds to it and registers the subordinate
buses as new i2c controllers.

-Scott

Re: I2C and CAN bus on MPC5200B device tree

[David Gibson]

On Mon, Jan 14, 2008 at 09:10:01AM +0100, Wolfgang Grandegger wrote:
> Grant Likely wrote:
> > On 1/13/08, Matt Sealey <matt@genesi-usa.com> wrote:
> >> 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";

These device_type entries should not be here.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson