linux-kernel - Re: [PATCH V3 3/6] coresight: etm4x: Drop pid argument from etm4

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Date:   Tue, 23 May 2023 07:58:13 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org
Cc:     Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
        Steve Clevenger <scclevenger@...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>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>, devicetree@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH V3 3/6] coresight: etm4x: Drop pid argument from
 etm4_probe()



On 5/19/23 18:08, Suzuki K Poulose wrote:
> On 19/05/2023 06:21, Anshuman Khandual wrote:
>> Coresight device pid can be retrieved from its iomem base address, which is
>> stored in 'struct etm4x_drvdata'. This drops pid argument from etm4_probe()
>> and 'struct etm4_init_arg'. Instead etm4_check_arch_features() derives the
>> coresight device pid with a new helper coresight_get_pid(), right before it
>> is consumed in etm4_hisi_match_pid().
>>
>> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
>> Cc: Suzuki K Poulose <suzuki.poulose@....com>
>> Cc: Mike Leach <mike.leach@...aro.org>
>> Cc: Leo Yan <leo.yan@...aro.org>
>> Cc: coresight@...ts.linaro.org
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>   .../coresight/coresight-etm4x-core.c          | 29 ++++++++++---------
>>   include/linux/coresight.h                     | 12 ++++++++
>>   2 files changed, 27 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> index 748d2ef53cb0..914ef6eb85d1 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> @@ -66,7 +66,6 @@ static u64 etm4_get_access_type(struct etmv4_config *config);
>>   static enum cpuhp_state hp_online;
>>     struct etm4_init_arg {
>> -    unsigned int        pid;
>>       struct device        *dev;
>>       struct csdev_access    *csa;
>>   };
>> @@ -370,9 +369,17 @@ static void etm4_disable_arch_specific(struct etmv4_drvdata *drvdata)
>>   }
>>     static void etm4_check_arch_features(struct etmv4_drvdata *drvdata,
>> -                      unsigned int id)
>> +                     struct csdev_access *csa)
>>   {
>> -    if (etm4_hisi_match_pid(id))
>> +    /*
>> +     * coresight_get_pid() fetches device PID from the iomem
>> +     * register based accesses, which cannot be performed on
>> +     * system instruction based devices.
>> +     */
> 
> Minor nit: Please fix the comment to say something like :
> 
>     /*
>      * TRCPIDR* registers are not required for ETMs with system
>      * instructions. They must be identified by the MIDR+REVIDRs.
>      * Skip the TRCPID checks for now.
>      */
> 
> Rest looks good to me.

Will change the in-code comment as suggested.