linux-kernel - Re: [PATCHv2 1/2] coresight: Do not default to CPU0 for missing CPU phandle

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Date:   Fri, 21 Jun 2019 16:03:49 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        mathieu.poirier@...aro.org, leo.yan@...aro.org, robh+dt@...nel.org,
        devicetree@...r.kernel.org, alexander.shishkin@...ux.intel.com,
        david.brown@...aro.org, mark.rutland@....com
Cc:     rnayak@...eaurora.org, vivek.gautam@...eaurora.org,
        sibis@...eaurora.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCHv2 1/2] coresight: Do not default to CPU0 for missing CPU
 phandle

Hello Suzuki,

On 6/21/2019 3:18 PM, Suzuki K Poulose wrote:
> Hi Sai,
> 
> 
> On 06/20/2019 07:31 PM, Sai Prakash Ranjan 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@...eaurora.org>
>> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
> 
> Please drop this tag for now.
> 

Ok will drop this.

>> ---
>>   Documentation/devicetree/bindings/arm/coresight.txt |  2 +-
>>   drivers/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    | 10 +++++-----
>>   5 files changed, 15 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/arm/coresight.txt 
>> b/Documentation/devicetree/bindings/arm/coresight.txt
>> index 8a88ddebc1a2..c4659ba9457d 100644
>> --- a/Documentation/devicetree/bindings/arm/coresight.txt
>> +++ b/Documentation/devicetree/bindings/arm/coresight.txt
>> @@ -88,7 +88,7 @@ its hardware characteristcs.
>>         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.
>> +      affinity is set to invalid.
> 
> Please move this from the "Optional properties". It is not "Optional"
> anymore with this change. Please make sure it is evident that this
> is mandatory. Also please fix the bindings document for cpu-debug.txt.
> 
> 
>>   * Optional property for TMC:
> 
>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c 
>> b/drivers/hwtracing/coresight/coresight-platform.c
>> index 3c5ceda8db24..8b03fa573684 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);
> 
> Please fix the acpi_coresight_get_cpu() for ACPI.
> 

Ok will do it. Thanks again for the review comments.

-Sai

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