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

[Jinlong Mao <quic_jinlmao@quicinc.com>]

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@quicinc.com>
>>>>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.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
>
>>>
>> 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 {
>>>>
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