linux-kernel - Re: [RFC PATCH v3 1/7] dt-bindings: arm: coresight-tmc: Add "memory-region" property

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Message-ID: <59bf237d-1645-8c44-94f2-72a0cf229595@arm.com>
Date:   Mon, 4 Sep 2023 09:26:49 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Linu Cherian <lcherian@...vell.com>, mike.leach@...aro.org,
        james.clark@....com, leo.yan@...aro.org
Cc:     linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        devicetree@...r.kernel.org, sgoutham@...vell.com,
        gcherian@...vell.com
Subject: Re: [RFC PATCH v3 1/7] dt-bindings: arm: coresight-tmc: Add
 "memory-region" property

On 04/09/2023 06:05, Linu Cherian wrote:
> memory-region 0: Reserved trace buffer memory
> 
>    TMC ETR: When available, use this reserved memory region for
>    trace data capture. Same region is used for trace data
>    retention after a panic or watchdog reset.
> 
>    TMC ETF: When available, use this reserved memory region for
>    trace data retention synced from internal SRAM after a panic or
>    watchdog reset.
> 
> memory-region 1: Reserved meta data memory
> 
>    TMC ETR, ETF: When available, use this memory for register
>    snapshot retention synced from hardware registers after a panic
>    or watchdog reset.

Instead of having to use a number to map the memory regions, could
we use

memory-region-names property to describe the index ? That way it
is much easier to read and is less error prone.

Names could be something like:

tmc-reserved-trace
tmc-reserved-metadata

Suzuki

> 
> Signed-off-by: Linu Cherian <lcherian@...vell.com>
> ---
>   .../devicetree/bindings/arm/arm,coresight-tmc.yaml  | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/arm/arm,coresight-tmc.yaml b/Documentation/devicetree/bindings/arm/arm,coresight-tmc.yaml
> index cb8dceaca70e..dce54978554a 100644
> --- a/Documentation/devicetree/bindings/arm/arm,coresight-tmc.yaml
> +++ b/Documentation/devicetree/bindings/arm/arm,coresight-tmc.yaml
> @@ -101,6 +101,17 @@ properties:
>             and ETF configurations.
>           $ref: /schemas/graph.yaml#/properties/port
>   
> +   memory-region:
> +    items:
> +      - description: Reserved trace buffer memory for ETR and ETF sinks.
> +        For ETR, this reserved memory region is used for trace data capture.
> +        Same region is used for trace data retention as well after a panic
> +        or watchdog reset.
> +        For ETF, this reserved memory region is used for retention of trace
> +        data synced from internal SRAM after a panic or watchdog reset.
> +
> +      - description: Reserved meta data memory. Used for ETR and ETF sinks.
> +
>   required:
>     - compatible
>     - reg
> @@ -115,6 +126,8 @@ examples:
>       etr@...70000 {
>           compatible = "arm,coresight-tmc", "arm,primecell";
>           reg = <0x20070000 0x1000>;
> +        memory-region = <&etr_trace_mem_reserved>,
> +                       <&etr_mdata_mem_reserved>;
>   
>           clocks = <&oscclk6a>;
>           clock-names = "apb_pclk";