[PATCH 19/19] dts: bindings: coresight: ETMv4.4 system register access only units

[Suzuki K Poulose]

On 09/18/2020 04:35 PM, Mike Leach wrote:
> On Fri, 11 Sep 2020 at 09:41, Suzuki K Poulose <suzuki.poulose at arm.com> wrote:
>>
>> Document the bindings for ETMv4.4 and later with only system register
>> access.
>>
>> Cc: devicetree at vger.kernel.org
>> Cc: Mathieu Poirier <mathieu.poirier at linaro.org>
>> Cc: Mike Leach <mike.leach at linaro.org>
>> Reviewed-by: Rob Herring <robh at kernel.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
>> ---
>>   Documentation/devicetree/bindings/arm/coresight.txt | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt
>> index d711676b4a51..cfe47bdda728 100644
>> --- a/Documentation/devicetree/bindings/arm/coresight.txt
>> +++ b/Documentation/devicetree/bindings/arm/coresight.txt
>> @@ -34,9 +34,13 @@ its hardware characteristcs.
>>                                          Program Flow Trace Macrocell:
>>                          "arm,coresight-etm3x", "arm,primecell";
>>
>> -               - Embedded Trace Macrocell (version 4.x):
>> +               - Embedded Trace Macrocell (version 4.x), with memory mapped access.
>>                          "arm,coresight-etm4x", "arm,primecell";
>>
>> +               - Embedded Trace Macrocell (version 4.4 and later) with system
>> +                 register access only.
>> +                       "arm,coresight-etm-v4.4";
> 
> Any version of ETM can implement register access - including those pre
> ETM 4.4. Perhaps the new name should simply reflect sys reg access
> rather than a version.
> 

You're right. I got it confused with the v8.4 SelfHosted Extensions, which
mandates the sysreg access and makes the mem I/O obsolete. How about :

	"arm,coresight-etm4x-sysreg" ?


> Given that the two compatibility strings should be mutually exclusive
> for a given device, should the bindings doc (or at least the etm4x
> component part) be re-written into the .yaml format so that this can
> be enforced?

I will take a look, haven't played with the yaml.

Thanks for the review !

Suzuki