RE: [PATCH 3/4] dt-bindings: i3c: Make 'assigned-address' valid if static address != 0

Vitor Soares
2019-08-29T14:06:10Z

Hi Boris,

From: Boris Brezillon <boris.brezillon@collabora.com>
Date: Thu, Aug 29, 2019 at 11:51:38

> On Thu, 29 Aug 2019 12:19:34 +0200
> Vitor Soares <Vitor.Soares@synopsys.com> wrote:
>
> > The I3C devices without a static address can require a specific dynamic
> > address for priority reasons.
> >
> > Let's update the binding document to make the 'assigned-address' property
> > valid if static address != 0 and add an example with this use case.
>
> ^ you mean static address == 0, right?

Indeed.

>
> Yes, it makes sense to support that case and do our best to assign the
> requested address after DAA has taken place by explicitly executing
> SETDA.
>
> >
> > Signed-off-by: Vitor Soares <vitor.soares@synopsys.com>
> > ---
> > Documentation/devicetree/bindings/i3c/i3c.txt | 13 ++++++++++---
> > 1 file changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/i3c/i3c.txt b/Documentation/devicetree/bindings/i3c/i3c.txt
> > index ab729a0..c851e75 100644
> > --- a/Documentation/devicetree/bindings/i3c/i3c.txt
> > +++ b/Documentation/devicetree/bindings/i3c/i3c.txt
> > @@ -98,9 +98,7 @@ Required properties
> >
> > Optional properties
> > -------------------
> > -- assigned-address: dynamic address to be assigned to this device. This
> > - property is only valid if the I3C device has a static
> > - address (first cell of the reg property != 0).
> > +- assigned-address: dynamic address to be assigned to this device.
>
> We should probably mention that we don't provide strong guarantees
> here. We will try to assign this dynamic address to the device, but if
> something fails (like another device owning the address and refusing to
> give it up), the actual dynamic address will be different.
> This clarification can be done in a separate patch.

So, another patch on top of this one explaining that, right?

I would suggest to use a dynamic address, like 0x40 (mid priority), on
ENTDAA so lowers addresses (High Priority) can be used in DT or another
method.

What do you think about this?

>
> >
> >
> > Example:
> > @@ -129,6 +127,15 @@ Example:
> >
> > /*
> > * I3C device without a static I2C address but requiring
> > + * specific dynamic address.
> > + */
> > + sensor@0,39200154004 {
> > + reg = <0x0 0x6072 0x303904d2>;
> > + assigned-address = <0xb>;
> > + };
> > +
> > + /*
> > + * I3C device without a static I2C address but requiring
> > * resources described in the DT.
> > */
> > sensor@0,39200154004 {

Best regards,
Vitor Soares