Re: [PATCH 00/20] coresight: Update device tree bindings

[Suzuki K Poulose]

On 05/06/18 22:43, Suzuki K Poulose wrote:
> Coresight uses DT graph bindings to describe the connections of the
> components. However we have some undocumented usage of the bindings
> to describe some of the properties of the connections.
>
> The coresight driver needs to know the hardware ports invovled
> in the connection and the direction of data flow to effectively
> manage the trace sessions. So far we have relied on the "port"
> address (as described by the generic graph bindings) to represent
> the hardware port of the component for a connection.

...

> There were three options considered for the hardware port number scheme:


...

>   3) Use explicit properties (implemented in the series) for the hardware
>      port id and direction. We define a new property "coresight,hwid" for
>      each endpoint in coresight devices to specify the hardware port number
>      explicitly. Also use a separate property "direction" to specify the
>      direction of the data flow.
>
> 	e.g,
>
> 	port@0{
> 		reg = <0>;
> 		endpoint {
> 			direction = <1>;	// Output
> 			coresight,hwid = <0>;	// Port # 0
> 		}
> 	};
>
> 	port@1{
> 		reg = <1>;
> 		endpoint {
> 			direction = <0>;	// Input
> 			coresight,hwid = <0>;	// Port # 0
> 		};
> 	};
>
>      Pros:
>         - The bindings are formal and reader friendly, and less prone to errors.
>      Cons:
>         - Backward compatibility is lost.
>
>
> This series implements Option (3) listed above and falls back to the old
> bindings if the new bindings are not available. This allows the systems
> with old bindings work with the new driver. The driver now issues a warning
> (once) when it encounters the old bindings.

 ....

>    dts: juno: Update coresight bindings for hw port
>    dts: hisilicon: Update coresight bindings for hw ports
>    dts: spreadtrum: Update coresight bindings for hw ports
>    dts: qcom: Update coresight bindings for hw ports
>    dts: arm: hisilicon: Update coresight bindings for hardware port
>    dts: arm: imx7{d,s}: Update coresight binding for hardware ports
>    dts: arm: omap: Update coresight bindings for hardware ports
>    dts: arm: qcom: Update coresight bindings for hardware ports
>    dts: sama5d2: Update coresight bindings for hardware ports
>    dts: ste-dbx5x0: Update coresight bindings for hardware port
>    dts: tc2: Update coresight bindings for hardware ports

All,

Pleas hold on with applying the DTS changes listed above. There are
still some on going discussions on the bindings and we are yet to
come to a conclusion [0]. And there are high chances that these might
change. Sorry for the inconvenience.

[0] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-June/582269.html

Kind regards
Suzuki