linux-kernel - Re: [PATCH V5 5/6] coresight: platform: acpi: Ignore the absence of graph

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Message-ID: <CAJ9a7ViWiSuabBVPASHO-MDs9z7wGSLuCLCpPezFrh6p3AOgyA@mail.gmail.com>
Date:   Wed, 7 Jun 2023 09:58:55 +0100
From:   Mike Leach <mike.leach@...aro.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org,
        suzuki.poulose@....com, scclevenger@...amperecomputing.com,
        Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Leo Yan <leo.yan@...aro.org>, devicetree@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V5 5/6] coresight: platform: acpi: Ignore the absence of graph

HI Ansuman,

On Mon, 29 May 2023 at 07:26, Anshuman Khandual
<anshuman.khandual@....com> wrote:
>
> From: Suzuki K Poulose <suzuki.poulose@....com>
>
> Some components may not have graph connections for describing
> the trace path. e.g., ETE, where it could directly use the per
> CPU TRBE. Ignore the absence of graph connections
>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
>  drivers/hwtracing/coresight/coresight-platform.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> index 475899714104..c4b4fbde8550 100644
> --- a/drivers/hwtracing/coresight/coresight-platform.c
> +++ b/drivers/hwtracing/coresight/coresight-platform.c
> @@ -692,8 +692,12 @@ static int acpi_coresight_parse_graph(struct acpi_device *adev,
>
>         pdata->nr_inport = pdata->nr_outport = 0;
>         graph = acpi_get_coresight_graph(adev);
> +       /*
> +        * There are no graph connections, which is fine for some components.
> +        * e.g., ETE
> +        */
>         if (!graph)
> -               return -ENOENT;
> +               return 0;
>

Should we not determine if it is valid for a particular component not
to have a graph connection?
Prior to this patch an incorrectly configured ETMv4 - which must have
a graph would return an error, after this it will fail silently

Mike

>         nlinks = graph->package.elements[2].integer.value;
>         if (!nlinks)
> --
> 2.25.1
>


-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK