Re: [PATCHv3 1/1] coresight: Do not default to CPU0 for missing CPU phandle

[Mathieu Poirier <mathieu.poirier@linaro.org>]

Hi Sai,

On Sun, 23 Jun 2019 at 21:36, Sai Prakash Ranjan
<saiprakash.ranjan@codeaurora.org> 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@codeaurora.org>
> ---
>  .../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 +++
>  drivers/hwtracing/coresight/coresight-platform.c | 16 ++++++++--------
>  6 files changed, 24 insertions(+), 13 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..4990da2c13e9 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;
>  }

Function of_coresight_get_cpu() needs to return -ENODEV rather than 0
when !CONFIG_OF

>
>  /*
> @@ -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;
>  }
>

Same as above, but for !CONFIG_ACPI

Thanks,
Mathieu

> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>

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