linux-kernel - Re: [PATCH v7 02/10] Coresight: Add coresight TPDM source driver

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Message-ID: <db16bdcc-9322-d81b-1afd-3955181ba2f7@quicinc.com>
Date:   Thu, 2 Jun 2022 11:14:02 +0800
From:   Jinlong Mao <quic_jinlmao@...cinc.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...aro.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <coresight@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Tao Zhang <quic_taozha@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Hao Zhang <quic_hazha@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v7 02/10] Coresight: Add coresight TPDM source driver


On 6/1/2022 5:56 PM, Jinlong Mao wrote:
>
> On 6/1/2022 5:30 PM, Suzuki K Poulose wrote:
>> On 01/06/2022 10:21, Jinlong Mao wrote:
>>> Hi Suzuki,
>>>
>>> On 5/24/2022 3:00 PM, Jinlong Mao wrote:
>>>> Hi Suzuki,
>>>>
>>>> Thank you for the review.
>>>>
>>>> On 5/23/2022 4:57 PM, Suzuki K Poulose wrote:
>>>>> Hi
>>>>>
>>>>> On 09/05/2022 14:39, Mao Jinlong wrote:
>>>>>> Add driver to support Coresight device TPDM (Trace, Profiling and
>>>>>> Diagnostics Monitor). TPDM is a monitor to collect data from
>>>>>> different datasets. This change is to add probe/enable/disable
>>>>>> functions for tpdm source.
>>>>>>
>>>>>> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
>>>>>> Signed-off-by: Mao Jinlong <quic_jinlmao@...cinc.com>
>>>>>> ---
>>>>>>   drivers/hwtracing/coresight/Kconfig          |  13 ++
>>>>>>   drivers/hwtracing/coresight/Makefile         |   1 +
>>>>>>   drivers/hwtracing/coresight/coresight-core.c |   5 +-
>>>>>>   drivers/hwtracing/coresight/coresight-tpdm.c | 146 
>>>>>> +++++++++++++++++++
>>>>>>   drivers/hwtracing/coresight/coresight-tpdm.h |  26 ++++
>>>>>>   include/linux/coresight.h                    |   1 +
>>>>>>   6 files changed, 191 insertions(+), 1 deletion(-)
>>>>>>   create mode 100644 drivers/hwtracing/coresight/coresight-tpdm.c
>>>>>>   create mode 100644 drivers/hwtracing/coresight/coresight-tpdm.h
>>>>>>
>>>
>>>>>> +/**
>>>>>> + * struct tpdm_drvdata - specifics associated to an TPDM component
>>>>>> + * @base:       memory mapped base address for this component.
>>>>>> + * @dev:        The device entity associated to this component.
>>>>>> + * @csdev:      component vitals needed by the framework.
>>>>>> + * @lock:       lock for the enable value.
>>>>>> + * @enable:     enable status of the component.
>>>>>> + */
>>>>>> +
>>>>>> +struct tpdm_drvdata {
>>>>>> +    void __iomem        *base;
>>>>>> +    struct device        *dev;
>>>>>> +    struct coresight_device    *csdev;
>>>>>> +    struct mutex        lock;
>>>>>
>>>>> Why mutex lock ? Couldn't this be a spinlock ?
>>>> 1. There is no irq for TPDM
>>>> 2. As there are 7 dataset types, there will be some FOR loop to 
>>>> configure
>>>> tpdm registers which may cause some time.
>>
>> How long does it take to configure ? Is it too long enough to trigger
>> RCU stalls ? as long as we don't do any sleeping/blocking operations
>> we should be fine with a spinlock.
>>
>> Suzuki
>
> Let me check on internal device and get back to you.
>
> Thanks
> Jinlong Mao

The time of configuring the registers doesn't reach RCU stall timeout value.

I will use spin_lock for both tpdm and tpda.

Thanks
Jinlong Mao
>>
>>>>
>>> I think we can use mutex lock here. Do you have any more comments 
>>> for this ?
>>
>>>
>>> Thanks
>>> Jinlong Mao
>>>>>
>>>>>> +    bool            enable;
>>>>>> +};
>>>>>> +
>>>>>> +#endif  /* _CORESIGHT_CORESIGHT_TPDM_H */
>>>>>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>>>>>> index 247147c11231..a9efac55029d 100644
>>>>>> --- a/include/linux/coresight.h
>>>>>> +++ b/include/linux/coresight.h
>>>>>> @@ -61,6 +61,7 @@ enum coresight_dev_subtype_source {
>>>>>>       CORESIGHT_DEV_SUBTYPE_SOURCE_PROC,
>>>>>>       CORESIGHT_DEV_SUBTYPE_SOURCE_BUS,
>>>>>>       CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE,
>>>>>> +    CORESIGHT_DEV_SUBTYPE_SOURCE_DATA_ONLY,
>>>>>
>>>>> super minor nit: I find the choice of name a bit odd.
>>>>> We could simply make it something like :
>>>>>
>>>>>     CORESIGHT_DEV_SUBTYPE_SOURCE_OTHERS:
>>>>>
>>>>> Suzuki
>>>> I will check and update.
>>>>>
>>>>>>   };
>>>>>>     enum coresight_dev_subtype_helper {
>>>>>
>>>>> _______________________________________________
>>>>> CoreSight mailing list -- coresight@...ts.linaro.org
>>>>> To unsubscribe send an email to coresight-leave@...ts.linaro.org
>>>> _______________________________________________
>>>> CoreSight mailing list -- coresight@...ts.linaro.org
>>>> To unsubscribe send an email to coresight-leave@...ts.linaro.org
>>
>> _______________________________________________
>> CoreSight mailing list -- coresight@...ts.linaro.org
>> To unsubscribe send an email to coresight-leave@...ts.linaro.org
> _______________________________________________
> CoreSight mailing list -- coresight@...ts.linaro.org
> To unsubscribe send an email to coresight-leave@...ts.linaro.org