On Wed, Jul 27, 2016 at 03:50:52PM -0600, Stephen Warren wrote: > On 07/26/2016 10:21 AM, Stephen Warren wrote: > > On 07/26/2016 04:03 AM, Thierry Reding wrote: > > > On Tue, Jul 19, 2016 at 01:14:41PM -0600, Stephen Warren wrote: > > > > From: Stephen Warren <swarren@xxxxxxxxxx> > > > > > > > > The BPMP implements some services which must be represented by separate > > > > nodes. For example, it can provide access to certain I2C controllers, > > > > and > > > > the I2C bindings represent each I2C controller as a device tree node. > > > > Update the binding to describe how the BPMP supports this. > > > > > > > > Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx> > > > > --- > > > > .../bindings/firmware/nvidia,tegra186-bpmp.txt | 23 > > > > ++++++++++++++++++++++ > > > > 1 file changed, 23 insertions(+) > > > > > > > > diff --git > > > > a/Documentation/devicetree/bindings/firmware/nvidia,tegra186-bpmp.txt > > > > b/Documentation/devicetree/bindings/firmware/nvidia,tegra186-bpmp.txt > > > > index 9a3864f56955..142d363406f6 100644 > > > > --- > > > > a/Documentation/devicetree/bindings/firmware/nvidia,tegra186-bpmp.txt > > > > +++ > > > > b/Documentation/devicetree/bindings/firmware/nvidia,tegra186-bpmp.txt > > > > @@ -38,6 +38,24 @@ implemented by this node: > > > > - .../reset/reset.txt > > > > - <dt-bindings/reset/tegra186-reset.h> > > > > > > > > +The BPMP implements some services which must be represented by > > > > separate nodes. > > > > +For example, it can provide access to certain I2C controllers, and > > > > the I2C > > > > +bindings represent each I2C controller as a device tree node. Such > > > > nodes should > > > > +be nested directly inside the main BPMP node. > > > > + > > > > +Software can determine whether a child node of the BPMP node > > > > represents a device > > > > +by checking for a compatible property. Any node with a compatible > > > > property > > > > +represents a device that can be instantiated. Nodes without a > > > > compatible > > > > +property may be used to provide configuration information regarding > > > > the BPMP > > > > +itself, although no such configuration nodes are currently defined > > > > by this > > > > +binding. > > > > + > > > > +The BPMP firmware defines no single global name-/numbering-space for > > > > such > > > > +services. Put another way, the numbering scheme for I2C buses is > > > > distinct from > > > > +the numbering scheme for any other service the BPMP may provide > > > > (e.g. a future > > > > +hypothetical SPI bus service). As such, child device nodes will have > > > > no reg > > > > +property, and the BPMP node will have no #address-cells or > > > > #size-cells property. > > > > > > My understanding is that the I2C bus number is passed as part of the > > > request to the BPMP firmware. Does that not count as addressing? Could > > > we not represent that generically using a device tree hierarchy? I'm > > > thinking something along these lines: > > > > > > bpmp { > > > ... > > > > > > services { > > > i2c { > > > i2c@0 { > > > reg = <0>; > > > > Technically, that is possible. However, Rob Herring rejected the idea of > > multiple levels of sub-nodes. > > > > Can we please just go with what we have? DT bindings are frankly an > > obstacle to getting anything done:-( > > Thierry, any further thoughts here? I really need to get these DT bindings > finalized so that I can use them in U-Boot, which is very urgent. Thanks. If everyone else is fine with these bindings, let's go ahead with them. Thierry
Attachment:
signature.asc
Description: PGP signature