linux-kernel - Re: [PATCH v2 09/10] coresight: Cleanup coresight DT bindings

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Date:   Wed, 25 Jul 2018 17:14:03 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Rob Herring <robh@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mathieu.poirier@...aro.org, sudeep.holla@....com,
        frowand.list@...il.com, devicetree@...r.kernel.org,
        mark.rutland@....com, matt.sealey@....com,
        charles.garcia-tobin@....com, coresight@...ts.linaro.org,
        john.horley@....com, mike.leach@...aro.org
Subject: Re: [PATCH v2 09/10] coresight: Cleanup coresight DT bindings

On 07/25/2018 05:09 PM, Rob Herring wrote:
> On Thu, Jul 19, 2018 at 11:55:13AM +0100, Suzuki K Poulose wrote:
>> The coresight drivers relied on default bindings for graph
>> in DT, while reusing the "reg" field of the "ports" to indicate
>> the actual hardware port number for the connections. This can
>> cause duplicate ports with same addresses, but different
>> direction. However, with the rules getting stricter w.r.t to the
>> address mismatch with the label, it is no longer possible to use
>> the port address field for the hardware port number.
>>
>> This patch introduces new DT binding rules for coresight
>> components, based on the same generic DT graph bindings, but
>> avoiding the address duplication.
>>
>> - All output ports must be specified under a child node with
>>    name "out-ports".
>> - All input ports must be specified under a childe node with
>>    name "in-ports".
>> - Port address should match the hardware port number.
>>
>> The support for legacy bindings is retained, with a warning.
>>
>> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
>> Cc: Sudeep Holla <sudeep.holla@....com>
>> Cc: Rob Herring <robh@...nel.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> ---
>>   .../devicetree/bindings/arm/coresight.txt          | 91 ++++++++++----------
>>   drivers/hwtracing/coresight/of_coresight.c         | 97 +++++++++++++++++++---
>>   2 files changed, 129 insertions(+), 59 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt
>> index 8e21512..f39d2c6 100644
>> --- a/Documentation/devicetree/bindings/arm/coresight.txt
>> +++ b/Documentation/devicetree/bindings/arm/coresight.txt
>> @@ -104,19 +104,9 @@ The connections must be described via generic DT graph bindings as described
>>   by the "bindings/graph.txt", where each "port" along with an "endpoint"
>>   component represents a hardware port and the connection.
>>   
>> -Since it is possible to have multiple connections for any coresight component
>> -with a specific direction of data flow, each connection must define the
>> -following properties to uniquely identify the connection details.
>> -
>> - * Direction of the data flow w.r.t the component :
>> -   Each input port must have the following property defined at the "endpoint"
>> -   for the port.
>> -	"slave-mode"
>> -
>> - * Hardware Port number at the component:
>> -     -  The hardware port number is assumed to be the address of the "port"
>> -         component.
>> -
> 
> Why do you add this in the previous patch and then remove it here?

The only use case I can think of it is for someone to look back on the
legacy bindings, which were never documented. I could skip the parts 
that are being removed.

Suzuki