Message-ID: <edbd1f10-70e5-1fd4-44de-da59b387e9dd@quicinc.com>
Date:   Tue, 28 Mar 2023 19:31:24 +0800
From:   Tao Zhang <quic_taozha@...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>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        James Clark <james.clark@....com>
CC:     Jinlong Mao <quic_jinlmao@...cinc.com>,
        Leo Yan <leo.yan@...aro.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        <coresight@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Hao Zhang <quic_hazha@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <andersson@...nel.org>
Subject: Re: [PATCH v3 02/11] coresight-tpda: Add DSB dataset support

Hi Suzuki,

On 3/27/2023 5:43 PM, Suzuki K Poulose wrote:
> On 27/03/2023 04:31, Tao Zhang wrote:
>>
>> On 3/26/2023 3:31 AM, Suzuki K Poulose wrote:
>>> On 24/03/2023 14:58, Tao Zhang wrote:
>>>> Hi Suzuki,
>>>>
>>>> 在 3/23/2023 7:51 PM, Suzuki K Poulose 写道:
>>>>> On 23/03/2023 06:03, Tao Zhang wrote:
>>>>>> Read the DSB element size from the device tree. Set the register
>>>>>> bit that controls the DSB element size of the corresponding port.
>>>>>>
>>>>>> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
>>>>>> ---
>>>>>>   drivers/hwtracing/coresight/coresight-tpda.c | 58 
>>>>>> ++++++++++++++++++++++++++++
>>>>>>   drivers/hwtracing/coresight/coresight-tpda.h |  4 ++
>>>>>>   2 files changed, 62 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/hwtracing/coresight/coresight-tpda.c 
>>>>>> b/drivers/hwtracing/coresight/coresight-tpda.c
>>>>>> index f712e11..8dcfc4a 100644
>>>>>> --- a/drivers/hwtracing/coresight/coresight-tpda.c
>>>>>> +++ b/drivers/hwtracing/coresight/coresight-tpda.c
>>>>>> @@ -21,6 +21,47 @@
>>>>>>     DEFINE_CORESIGHT_DEVLIST(tpda_devs, "tpda");
>>>>>>   +/* Search and read element data size from the TPDM node in
>>>>>> + * the devicetree. Each input port of TPDA is connected to
>>>>>> + * a TPDM. Different TPDM supports different types of dataset,
>>>>>> + * and some may support more than one type of dataset.
>>>>>> + * Parameter "inport" is used to pass in the input port number
>>>>>> + * of TPDA, and it is set to 0 in the recursize call.
>>>>>> + * Parameter "parent" is used to pass in the original call.
>>>>>> + */
>>>>>
>>>>> I am still not clear why we need to do this recursively ?
>>>>
>>>> Some TPDMs are not directly output connected to the TPDAs. So here I
>>>>
>>>> use a recursive method to check from the TPDA input port until I find
>>>>
>>>> the connected TPDM.
>>>>
>>>> Do you have a better suggestion besides a recursive method?
>>>>
>>>>>
>>>>>> +static int tpda_set_element_size(struct tpda_drvdata *drvdata,
>>>>>> +               struct coresight_device *csdev, int inport, bool 
>>>>>> parent)
>>>>>
>>>>> Please could we renamse csdev => tpda_dev
>>>>
>>>> Since this is a recursively called function, this Coresight device 
>>>> is not
>>>>
>>>> necessarily TPDA, it can be other Coresight device.
>>>>
>>>>>
>>>>>> +{
>>>>>> +    static int nr_inport;
>>>>>> +    int i;
>>>>>> +    struct coresight_device *in_csdev;
>>>>>
>>>>> similarly tpdm_dev ?
>>>> Same as above, this variable may not necessarily be a TPDM.
>>>>>
>>>>> Could we not add a check here to see if the dsb_esize[inport] is 
>>>>> already
>>>>> set and then bail out, reading this over and over ?
>>>>>
>>>> I will update this in the next patch series.
>>>>>> +
>>>>>> +    if (inport > (TPDA_MAX_INPORTS - 1))
>>>>>> +        return -EINVAL;
>>>>>> +
>>>>>> +    if (parent)
>>>>>> +        nr_inport = inport;
>>>>>> +
>>>>>> +    for (i = 0; i < csdev->pdata->nr_inconns; i++) {
>>>>>> +        in_csdev = csdev->pdata->in_conns[i].remote_dev;
>>>>>
>>>>> Please note, the names of the structure field might change in the
>>>>> next version of James' series
>>>> Got it. I will keep an eye out for the James' patch series.
>>>>>
>>>>>> +        if (!in_csdev)
>>>>>> +            break;
>>>>>> +
>>>>>> +        if (parent)
>>>>>> +            if (csdev->pdata->in_conns[i].port != inport)
>>>>>> +                continue;
>>>>>> +
>>>>>> +        if (in_csdev && strstr(dev_name(&in_csdev->dev), "tpdm")) {
>>>>>
>>>>> Isn't there a better way to distinguish a device to be TPDM ? May 
>>>>> be we
>>>>> could even add a source_sub_type - SOURCE_TPDM instead of using
>>>>> SOURCE_OTHERS ? Do you expect other sources to be connected to TPDA?
>>>>> e.g., STMs ?
>>>>
>>>> I can add "SOURCE_TPDM" as a source_sub_type, but SOURCE_OTHERS needs
>>>>
>>>> to be kept since the other Coresight component we will upstream 
>>>> later may
>>>>
>>>> need it.
>>>>
>>>>>
>>>>>> + of_property_read_u32(in_csdev->dev.parent->of_node,
>>>>>> +                    "qcom,dsb-element-size", 
>>>>>> &drvdata->dsb_esize[nr_inport]);
>>>>>> +            break;
>>>>>> +        }
>>>>>> +        tpda_set_element_size(drvdata, in_csdev, 0, false);
>>>>>
>>>>> What is the point of this ? Is this for covering the a TPDA 
>>>>> connected to
>>>>> another TPDA ?
>>>>>
>>>>> e.g., { TPDM0, TPDM1 } -> TPDA0 -> TPDA1 ?
>>>>
>>>> A TPDM may not connect to the TPDA directly, for example,
>>>>
>>>> TPDM0 ->FUNNEL0->FUNNEL1->TPDA0
>>>>
>>>> And many TPDMs can connect to one TPDA, one input port on TPDA only 
>>>> has
>>>>
>>>> one TPDM connected. Therefore, we use a recursive method to find 
>>>> the TPDM
>>>>
>>>> corresponding to the input port of TPDA.
>>>
>>> How do you find out decide what to choose, if there are multiple TPDMs
>>> connected to FUNNEL0 or even FUNNEL1 ?
>>>
>>> e.g
>>>
>>> TPDM0->FUNNEL0->FUNNEL1->TPDA0
>>>                 /
>>>           TPDM1
>>
>> We can find out the corresponding TPDM by the input port number of TPDA.
>>
>> Each input port is connected to a TPDM. So we have an input port 
>> number in
>>
>> the input parameter of the recursive lookup function 
>> "tpda_set_element_size".
>
> I don't understand, how you would figure out, in the above situation.
> i.e., FUNNEL1 is connected to TPDA0, but there are two TPDMs that could
> be pumping the trace. They both arrive via FUNNEL1. So, how does that
> solve your problem ?

In our HW design, the input ports of TPDA and TPDM are one-one-one 
corresponding.  Only one

TPDM can be found connected from one TPDA's input port. The path to a 
TPDA input port doesn't

connect more than one TPDM. It's by HW design.


Tao

>
> Suzuki
>
>
>>
>>> Suzuki
>>>
>>>
>

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