linux-kernel - Re: [PATCH RFC 1/3] coresight: binding for coresight debug driver

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Date:   Wed, 15 Feb 2017 13:08:58 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Wei Xu <xuwei5@...ilicon.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Daniel Thompson <daniel.thompson@...aro.org>
Subject: Re: [PATCH RFC 1/3] coresight: binding for coresight debug driver

On Mon, Feb 13, 2017 at 02:11:36PM +0800, Leo Yan wrote:
> Adding compatible string for new coresight debug driver.
> 

Hi Leo,

I agree with Mark, this will need a better description.

> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  Documentation/devicetree/bindings/arm/coresight.txt | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt
> index fcbae6a..3ff15fd 100644
> --- a/Documentation/devicetree/bindings/arm/coresight.txt
> +++ b/Documentation/devicetree/bindings/arm/coresight.txt
> @@ -40,6 +40,9 @@ its hardware characteristcs.
>  		- System Trace Macrocell:
>  			"arm,coresight-stm", "arm,primecell"; [1]
>  
> +		- Debug Unit:
> +			"arm,coresight-debug", "arm,primecell";
> +

Humm...  The current CoreSight bindings are meant to describe IPs included in
the HW assisted trace architecture.  This new driver, althought considered to be
part of the CoreSight umbrella, falls under the debugging domain.

Adding the bindings in this file may lead people to beleive this driver fits
into the CoreSight framework currently supported, which isn't the case.

As such it is probably a good idea to spin off a new file, "coresight-debug.txt"
to handle this driver. 

Mark, what's your take on this?

>  	* reg: physical base address and length of the register
>  	  set(s) of the component.
>  
> @@ -78,8 +81,10 @@ its hardware characteristcs.
>  	* arm,cp14: must be present if the system accesses ETM/PTM management
>  	  registers via co-processor 14.
>  
> -	* cpu: the cpu phandle this ETM/PTM is affined to. When omitted the
> -	  source is considered to belong to CPU0.
> +* Optional properties for ETM/PTM/Debugs:
> +
> +	* cpu: the cpu phandle this ETM/PTM/Debug is affined to. When omitted
> +	  the source is considered to belong to CPU0.
>  
>  * Optional property for TMC:
>  
> -- 
> 2.7.4
>