Re: [RESEND PATCHv4 1/1] coresight: Do not default to CPU0 for missing CPU phandle

[Mathieu Poirier]

On Wed, 26 Jun 2019 at 22:45, Sai Prakash Ranjan
<saiprakash.ranjan@xxxxxxxxxxxxxx> wrote:
>
> Coresight platform support assumes that a missing "cpu" phandle
> defaults to CPU0. This could be problematic and unnecessarily binds
> components to CPU0, where they may not be. Let us make the DT binding
> rules a bit stricter by not defaulting to CPU0 for missing "cpu"
> affinity information.
>
> Also in coresight etm and cpu-debug drivers, abort the probe
> for such cases.
>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
>  .../bindings/arm/coresight-cpu-debug.txt      |  4 ++--
>  .../devicetree/bindings/arm/coresight.txt     |  8 +++++---
>  .../hwtracing/coresight/coresight-cpu-debug.c |  3 +++
>  drivers/hwtracing/coresight/coresight-etm3x.c |  3 +++
>  drivers/hwtracing/coresight/coresight-etm4x.c |  3 +++
>  .../hwtracing/coresight/coresight-platform.c  | 20 +++++++++----------
>  6 files changed, 26 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt b/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt
> index 298291211ea4..f1de3247c1b7 100644
> --- a/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt
> +++ b/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt
> @@ -26,8 +26,8 @@ Required properties:
>                 processor core is clocked by the internal CPU clock, so it
>                 is enabled with CPU clock by default.
>
> -- cpu : the CPU phandle the debug module is affined to. When omitted
> -       the module is considered to belong to CPU0.
> +- cpu : the CPU phandle the debug module is affined to. Do not assume it
> +        to default to CPU0 if omitted.
>
>  Optional properties:
>
> diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt
> index 8a88ddebc1a2..fcc3bacfd8bc 100644
> --- a/Documentation/devicetree/bindings/arm/coresight.txt
> +++ b/Documentation/devicetree/bindings/arm/coresight.txt
> @@ -59,6 +59,11 @@ its hardware characteristcs.
>
>         * port or ports: see "Graph bindings for Coresight" below.
>
> +* Additional required property for Embedded Trace Macrocell (version 3.x and
> +  version 4.x):
> +       * cpu: the cpu phandle this ETM/PTM is affined to. Do not
> +         assume it to default to CPU0 if omitted.
> +
>  * Additional required properties for System Trace Macrocells (STM):
>         * reg: along with the physical base address and length of the register
>           set as described above, another entry is required to describe the
> @@ -87,9 +92,6 @@ 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 property for TMC:
>
>         * arm,buffer-size: size of contiguous buffer space for TMC ETR
> diff --git a/drivers/hwtracing/coresight/coresight-cpu-debug.c b/drivers/hwtracing/coresight/coresight-cpu-debug.c
> index 07a1367c733f..58bfd6319f65 100644
> --- a/drivers/hwtracing/coresight/coresight-cpu-debug.c
> +++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c
> @@ -579,6 +579,9 @@ static int debug_probe(struct amba_device *adev, const struct amba_id *id)
>                 return -ENOMEM;
>
>         drvdata->cpu = coresight_get_cpu(dev);
> +       if (drvdata->cpu < 0)
> +               return drvdata->cpu;
> +
>         if (per_cpu(debug_drvdata, drvdata->cpu)) {
>                 dev_err(dev, "CPU%d drvdata has already been initialized\n",
>                         drvdata->cpu);
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
> index 225c2982e4fe..e2cb6873c3f2 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
> @@ -816,6 +816,9 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
>         }
>
>         drvdata->cpu = coresight_get_cpu(dev);
> +       if (drvdata->cpu < 0)
> +               return drvdata->cpu;
> +
>         desc.name  = devm_kasprintf(dev, GFP_KERNEL, "etm%d", drvdata->cpu);
>         if (!desc.name)
>                 return -ENOMEM;
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index 7fe266194ab5..7bcac8896fc1 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -1101,6 +1101,9 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
>         spin_lock_init(&drvdata->spinlock);
>
>         drvdata->cpu = coresight_get_cpu(dev);
> +       if (drvdata->cpu < 0)
> +               return drvdata->cpu;
> +
>         desc.name = devm_kasprintf(dev, GFP_KERNEL, "etm%d", drvdata->cpu);
>         if (!desc.name)
>                 return -ENOMEM;
> diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> index 3c5ceda8db24..cf580ffbc27c 100644
> --- a/drivers/hwtracing/coresight/coresight-platform.c
> +++ b/drivers/hwtracing/coresight/coresight-platform.c
> @@ -159,16 +159,16 @@ static int of_coresight_get_cpu(struct device *dev)
>         struct device_node *dn;
>
>         if (!dev->of_node)
> -               return 0;
> +               return -ENODEV;
> +
>         dn = of_parse_phandle(dev->of_node, "cpu", 0);
> -       /* Affinity defaults to CPU0 */
>         if (!dn)
> -               return 0;
> +               return -ENODEV;
> +
>         cpu = of_cpu_node_to_id(dn);
>         of_node_put(dn);
>
> -       /* Affinity to CPU0 if no cpu nodes are found */
> -       return (cpu < 0) ? 0 : cpu;
> +       return cpu;
>  }
>
>  /*
> @@ -310,7 +310,7 @@ of_get_coresight_platform_data(struct device *dev,
>
>  static inline int of_coresight_get_cpu(struct device *dev)
>  {
> -       return 0;
> +       return -ENODEV;
>  }
>  #endif
>
> @@ -734,14 +734,14 @@ static int acpi_coresight_get_cpu(struct device *dev)
>         struct acpi_device *adev = ACPI_COMPANION(dev);
>
>         if (!adev)
> -               return 0;
> +               return -ENODEV;
>         status = acpi_get_parent(adev->handle, &cpu_handle);
>         if (ACPI_FAILURE(status))
> -               return 0;
> +               return -ENODEV;
>
>         cpu = acpi_handle_to_logical_cpuid(cpu_handle);
>         if (cpu >= nr_cpu_ids)
> -               return 0;
> +               return -ENODEV;
>         return cpu;
>  }
>
> @@ -769,7 +769,7 @@ acpi_get_coresight_platform_data(struct device *dev,
>
>  static inline int acpi_coresight_get_cpu(struct device *dev)
>  {
> -       return 0;
> +       return -ENODEV;
>  }
>  #endif

Thank you for adding this.

I want to apply your code to my tree but it isn't easy for me to do
so.  Did you notice the checkpatch.pl warning about the DT bindings
being in a separate patch?  In this case it is not a new binding but
following the process gives the DT maintainers the opportunity to at
least look at your patch.  Because the changes are trivial they may
decide to ignore it but that choice it theirs to make.

Regards,
Mathieu

>
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