linux-kernel - Re: [PATCH v2 05/27] dts: bindings: Document device tree binding for CATU

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Date:   Thu, 3 May 2018 11:42:56 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, Mike Leach <mike.leach@...aro.org>,
        Robert Walker <robert.walker@....com>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Frank Rowand <frowand.list@...il.com>,
        John Horley <john.horley@....com>, devicetree@...r.kernel.org,
        Mathieu Poirier <mathieu.poirier@....com>
Subject: Re: [PATCH v2 05/27] dts: bindings: Document device tree binding for CATU

On 1 May 2018 at 07:10, Rob Herring <robh@...nel.org> wrote:
> On Tue, May 01, 2018 at 10:10:35AM +0100, Suzuki K Poulose wrote:
>> Document CATU device-tree bindings. CATU augments the TMC-ETR
>> by providing an improved Scatter Gather mechanism for streaming
>> trace data to non-contiguous system RAM pages.
>>
>> Cc: devicetree@...r.kernel.org
>> Cc: frowand.list@...il.com
>> Cc: Rob Herring <robh@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: Mathieu Poirier <mathieu.poirier@....com>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> ---
>>  .../devicetree/bindings/arm/coresight.txt          | 52 ++++++++++++++++++++++
>>  1 file changed, 52 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt
>> index 15ac8e8..cdd84d0 100644
>> --- a/Documentation/devicetree/bindings/arm/coresight.txt
>> +++ b/Documentation/devicetree/bindings/arm/coresight.txt
>> @@ -39,6 +39,8 @@ its hardware characteristcs.
>>
>>               - System Trace Macrocell:
>>                       "arm,coresight-stm", "arm,primecell"; [1]
>> +             - Coresight Address Translation Unit (CATU)
>> +                     "arm, coresight-catu", "arm,primecell";
>
> spurious space               ^
>
>>
>>       * reg: physical base address and length of the register
>>         set(s) of the component.
>> @@ -86,6 +88,9 @@ its hardware characteristcs.
>>       * arm,buffer-size: size of contiguous buffer space for TMC ETR
>>        (embedded trace router)
>>
>> +* Optional property for CATU :
>> +     * interrupts : Exactly one SPI may be listed for reporting the address
>> +       error
>
> Somewhere you need to define the ports for the CATU.
>
>>
>>  Example:
>>
>> @@ -118,6 +123,35 @@ Example:
>>               };
>>       };
>>
>> +     etr@...70000 {
>> +             compatible = "arm,coresight-tmc", "arm,primecell";
>> +             reg = <0 0x20070000 0 0x1000>;
>> +
>> +             clocks = <&oscclk6a>;
>> +             clock-names = "apb_pclk";
>> +             ports {
>> +                     #address-cells = <1>;
>> +                     #size-cells = <0>;
>> +
>> +                     /* input port */
>> +                     port@0 {
>> +                             reg =  <0>;
>> +                             etr_in_port: endpoint {
>> +                                     slave-mode;
>> +                                     remote-endpoint = <&replicator2_out_port0>;
>> +                             };
>> +                     };
>> +
>> +                     /* CATU link represented by output port */
>> +                     port@1 {
>> +                             reg = <0>;
>
> While common in the Coresight bindings, having unit-address and reg not
> match is an error. Mathieu and I discussed this a bit as dtc now warns
> on these.
>
> Either reg should be 1 here, or 'ports' needs to be split into input and
> output ports. My preference would be the former, but Mathieu objected to
> this not reflecting the the h/w numbering.

Suzuki, as we discuss this is related to your work on revamping CS
bindings for ACPI.  Until that gets done and to move forward with this
set I suggest you abide to Rob's request.

>
> Rob