Re: DTS device tree node for dual port RAM

[Grant Likely <grant.likely@secretlab.ca>]

On Thu, Mar 12, 2009 at 5:24 AM, EXTERNAL Lange Matthias (AA-DGW/ENG1)
<Matthias.Lange@beissbarth.com> wrote:
> Hi,
>
> I am working on a MPC5200-based board. There is a dual port RAM connected=
 to the MPC5200 via the localbus. In my setup one can raise an interrupt at=
 the MPC5200 to signal new that new data has arrived in the dual port RAM. =
I have already found out that the interrupt delivery actually works (do_IRQ=
 gets called when raising the interrupt).
>
> My problem is that my driver (kernel 2.6.24) can not register for the int=
errupt. Each time I call request_irq I get -ENOSYS. I am suspecting that I =
have done something wrong in my dts defining the dual port RAM. I have defi=
ned the device as follows
>
> localbus {
> =A0 =A0 =A0 =A0compatible =3D "fsl,orion-localbus",
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "fsl,mpc5200-localbus",
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "fsl,pq2-localbus";

This should be: compatible =3D "fsl,mpc5200b-lpb","fsl,mpc5200-lpb","simple=
-bus";

It doesn't make much sense to claim compatibility with fsl,orion or
fsl,pq2 because the mpc5200 localbus is neither of those.

> =A0 =A0 =A0 =A0#address-cells =3D <2>;
> =A0 =A0 =A0 =A0#size-cells =3D <1>;
> =A0 =A0 =A0 =A0reg =3D <f0010100 40>;
> =A0 =A0 =A0 =A0ranges =3D <0 0 fe000000 00400000>;
>
> =A0 =A0 =A0 =A0dpram@40000000 {
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0device_type =3D "dpram";

Don't use device_type.  It doesn't make any sense in the flattened
device tree.  Use a compatible value instead, and prefix dpram with
the vendor and board name of the platform.  ie: compatible =3D
"<company>,<board>-dpram".  You should also document what this
compatible value means in Documentation/powerpc/device-tree/

> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0interrupts =3D <0 0 0>;

What hardware irq# are you using?  See this link for a description of
what the interrupts property should look like for external IRQs:

http://patchwork.ozlabs.org/patch/11349/

To use this property, the irq_of_parse_and_map() function will
translate from the device tree to a Linux IRQ number.

> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0interrupt-parent =3D <&mpc5200_pic>;

You probably also want a reg =3D <0 0 0x00400000>; property for mapping
the address range.

> =A0 =A0 =A0 =A0};
> };
>
> What am I doing wrong? What am I missing?
>
> Thanks,
> Matthias Lange.
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>



--=20
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.