On 07/20/2016 07:16 AM, Rob Herring 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. + The shared memory bindings for BPMP ----------------------------------- @@ -78,4 +96,9 @@ bpmp { #clock-cells = <1>; #power-domain-cells = <1>; #reset-cells = <1>; + + bpmp-i2c {Just 'i2c' here. With that: Acked-by: Rob Herring <robh@xxxxxxxxxx>
What if we have multiple BPMP I2C buses? The node names need to be unique, and there's no concept of register number so we can't use a unit address to do that.
I guess we could go for plain "i2c" for now and defer the more general naming discussion until some later point if/when we actually instantiate multiple buses, but I would like to confirm we can solve the problem if/when that time comes.
(As an aside, "pwr-i2c" might be a better name for the current bus, when the time comes, since any/all I2C nodes inside the BPMP would be BPMP I2C buses).
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