Message-ID: <d449d8ce-d087-4e18-a35a-236daa82ae99@arm.com>
Date: Mon, 8 Jan 2024 10:42:37 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Tao Zhang <quic_taozha@...cinc.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>
Cc: Jinlong Mao <quic_jinlmao@...cinc.com>,
 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>, Song Chai <quic_songchai@...cinc.com>,
 linux-arm-msm@...r.kernel.org, andersson@...nel.org
Subject: Re: [PATCH v3 6/8] coresight-tpdm: Add timestamp control register
 support for the CMB

On 05/01/2024 07:49, Tao Zhang wrote:
> 
> On 12/30/2023 5:39 PM, Suzuki K Poulose wrote:
>> On 25/12/2023 01:55, Tao Zhang wrote:
>>>
>>> On 12/20/2023 7:07 PM, Suzuki K Poulose wrote:
>>>> On 20/12/2023 09:51, Tao Zhang wrote:
>>>>>
>>>>> On 12/19/2023 9:51 PM, Suzuki K Poulose wrote:
>>>>>> On 19/12/2023 02:43, Tao Zhang wrote:
>>>>>>>
>>>>>>> On 12/18/2023 6:46 PM, Suzuki K Poulose wrote:
>>>>>>>> On 21/11/2023 02:24, Tao Zhang wrote:
>>>>>>>>> CMB_TIER register is CMB subunit timestamp insertion enable 
>>>>>>>>> register.
>>>>>>>>> Bit 0 is PATT_TSENAB bit. Set this bit to 1 to request a timestamp
>>>>>>>>> following a CMB interface pattern match. Bit 1 is XTRIG_TSENAB 
>>>>>>>>> bit.
>>>>>>>>> Set this bit to 1 to request a timestamp following a CMB CTI 
>>>>>>>>> timestamp
>>>>>>>>> request. Bit 2 is TS_ALL bit. Set this bit to 1 to request 
>>>>>>>>> timestamp
>>>>>>>>> for all packets.
>>>>>>>>>
>>>>>>>>> Reviewed-by: James Clark <james.clark@....com>
>>>>>>>>> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
>>>>>>>>> Signed-off-by: Jinlong Mao <quic_jinlmao@...cinc.com>
>>>>>>>>> ---
>>>>>>>>>   .../testing/sysfs-bus-coresight-devices-tpdm  | 35 ++++++
>>>>>>>>>   drivers/hwtracing/coresight/coresight-tpdm.c  | 116 
>>>>>>>>> +++++++++++++++++-
>>>>>>>>>   drivers/hwtracing/coresight/coresight-tpdm.h  | 14 +++
>>>>>>>>>   3 files changed, 162 insertions(+), 3 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git 
>>>>>>>>> a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm 
>>>>>>>>> b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
>>>>>>>>> index 53662ce7c2d0..e0b77107be13 100644
>>>>>>>>> --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
>>>>>>>>> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
>>>>>>>>> @@ -214,3 +214,38 @@ KernelVersion    6.7
>>>>>>>>>   Contact:    Jinlong Mao (QUIC) <quic_jinlmao@...cinc.com>, 
>>>>>>>>> Tao Zhang (QUIC) <quic_taozha@...cinc.com>
>>>>>>>>>   Description:
>>>>>>>>>           (RW) Set/Get the mask of the pattern for the CMB 
>>>>>>>>> subunit TPDM.
>>>>>>>>> +
>>>>>>>>> +What: /sys/bus/coresight/devices/<tpdm-name>/cmb_patt/enable_ts
>>>>>>>>> +Date:        September 2023
>>>>>>>>> +KernelVersion    6.7
>>>>>>>>> +Contact:    Jinlong Mao (QUIC) <quic_jinlmao@...cinc.com>, Tao 
>>>>>>>>> Zhang (QUIC) <quic_taozha@...cinc.com>
>>>>>>>>> +Description:
>>>>>>>>> +        (Write) Set the pattern timestamp of CMB tpdm. Read
>>>>>>>>> +        the pattern timestamp of CMB tpdm.
>>>>>>>>> +
>>>>>>>>> +        Accepts only one of the 2 values -  0 or 1.
>>>>>>>>> +        0 : Disable CMB pattern timestamp.
>>>>>>>>> +        1 : Enable CMB pattern timestamp.
>>>>>>>>> +
>>>>>>>>> +What: /sys/bus/coresight/devices/<tpdm-name>/cmb_trig_ts
>>>>>>>>> +Date:        September 2023
>>>>>>>>> +KernelVersion    6.7
>>>>>>>>> +Contact:    Jinlong Mao (QUIC) <quic_jinlmao@...cinc.com>, Tao 
>>>>>>>>> Zhang (QUIC) <quic_taozha@...cinc.com>
>>>>>>>>> +Description:
>>>>>>>>> +        (RW) Set/Get the trigger timestamp of the CMB for tpdm.
>>>>>>>>> +
>>>>>>>>> +        Accepts only one of the 2 values -  0 or 1.
>>>>>>>>> +        0 : Set the CMB trigger type to false
>>>>>>>>> +        1 : Set the CMB trigger type to true
>>>>>>>>> +
>>>>>>>>> +What: /sys/bus/coresight/devices/<tpdm-name>/cmb_ts_all
>>>>>>>>> +Date:        September 2023
>>>>>>>>> +KernelVersion    6.7
>>>>>>>>> +Contact:    Jinlong Mao (QUIC) <quic_jinlmao@...cinc.com>, Tao 
>>>>>>>>> Zhang (QUIC) <quic_taozha@...cinc.com>
>>>>>>>>> +Description:
>>>>>>>>> +        (RW) Read or write the status of timestamp upon all 
>>>>>>>>> interface.
>>>>>>>>> +        Only value 0 and 1  can be written to this node. Set 
>>>>>>>>> this node to 1 to requeset
>>>>>>>>> +        timestamp to all trace packet.
>>>>>>>>> +        Accepts only one of the 2 values -  0 or 1.
>>>>>>>>> +        0 : Disable the timestamp of all trace packets.
>>>>>>>>> +        1 : Enable the timestamp of all trace packets.
>>>>>>>>> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c 
>>>>>>>>> b/drivers/hwtracing/coresight/coresight-tpdm.c
>>>>>>>>> index 894d4309f1c7..f6cda5616e84 100644
>>>>>>>>> --- a/drivers/hwtracing/coresight/coresight-tpdm.c
>>>>>>>>> +++ b/drivers/hwtracing/coresight/coresight-tpdm.c
>>>>>>>>> @@ -331,6 +331,36 @@ static void tpdm_enable_dsb(struct 
>>>>>>>>> tpdm_drvdata *drvdata)
>>>>>>>>>       writel_relaxed(val, drvdata->base + TPDM_DSB_CR);
>>>>>>>>>   }
>>>>>>>>>   +static void set_cmb_tier(struct tpdm_drvdata *drvdata)
>>>>>>>>> +{
>>>>>>>>> +    u32 val;
>>>>>>>>> +
>>>>>>>>> +    val = readl_relaxed(drvdata->base + TPDM_CMB_TIER);
>>>>>>>>> +
>>>>>>>>> +    /* Clear all relevant fields */
>>>>>>>>> +    val &= ~(TPDM_CMB_TIER_PATT_TSENAB | TPDM_CMB_TIER_TS_ALL |
>>>>>>>>> +         TPDM_CMB_TIER_XTRIG_TSENAB);
>>>>>>>>> +
>>>>>>>>> +    /* Set pattern timestamp type and enablement */
>>>>>>>>> +    if (drvdata->cmb->patt_ts)
>>>>>>>>> +        val |= TPDM_CMB_TIER_PATT_TSENAB;
>>>>>>>>
>>>>>>>>  -- cut --
>>>>>>>>> +    else
>>>>>>>>> +        val &= ~TPDM_CMB_TIER_PATT_TSENAB;
>>>>>>>>
>>>>>>>>
>>>>>>>> All the else cases in this function are superfluous. Please 
>>>>>>>> remove all
>>>>>>>> of them.
>>>>>>> I will update this in the next patch.
>>>>>>>>
>>>>>>>>> +
>>>>>>>>> +    /* Set trigger timestamp */
>>>>>>>>> +    if (drvdata->cmb->trig_ts)
>>>>>>>>> +        val |= TPDM_CMB_TIER_XTRIG_TSENAB;
>>>>>>>>> +    else
>>>>>>>>> +        val &= ~TPDM_CMB_TIER_XTRIG_TSENAB;
>>>>>>>>> +
>>>>>>>>> +    /* Set all timestamp enablement*/
>>>>>>>>> +    if (drvdata->cmb->ts_all)
>>>>>>>>> +        val |= TPDM_CMB_TIER_TS_ALL;
>>>>>>>>> +    else
>>>>>>>>> +        val &= ~TPDM_CMB_TIER_TS_ALL;
>>>>>>>>> +    writel_relaxed(val, drvdata->base + TPDM_CMB_TIER);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>>   static void tpdm_enable_cmb(struct tpdm_drvdata *drvdata)
>>>>>>>>>   {
>>>>>>>>>       u32 val, i;
>>>>>>>>> @@ -347,6 +377,8 @@ static void tpdm_enable_cmb(struct 
>>>>>>>>> tpdm_drvdata *drvdata)
>>>>>>>>>                   drvdata->base + TPDM_CMB_XPMR(i));
>>>>>>>>>       }
>>>>>>>>>   +    set_cmb_tier(drvdata);
>>>>>>>>> +
>>>>>>>>>       val = readl_relaxed(drvdata->base + TPDM_CMB_CR);
>>>>>>>>>       /*
>>>>>>>>>        * Set to 0 for continuous CMB collection mode,
>>>>>>>>> @@ -695,9 +727,17 @@ static ssize_t enable_ts_show(struct 
>>>>>>>>> device *dev,
>>>>>>>>>                     char *buf)
>>>>>>>>>   {
>>>>>>>>>       struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
>>>>>>>>> +    ssize_t size = 0;
>>>>>>>>>   -    return sysfs_emit(buf, "%u\n",
>>>>>>>>> -             (unsigned int)drvdata->dsb->patt_ts);
>>>>>>>>> +    if (tpdm_has_dsb_dataset(drvdata))
>>>>>>>>> +        size = sysfs_emit(buf, "%u\n",
>>>>>>>>> +                 (unsigned int)drvdata->dsb->patt_ts);
>>>>>>>>> +
>>>>>>>>> +    if (tpdm_has_cmb_dataset(drvdata))
>>>>>>>>> +        size = sysfs_emit(buf, "%u\n",
>>>>>>>>> +                 (unsigned int)drvdata->cmb->patt_ts);
>>>>>>>>
>>>>>>>> Why does this need to show two values ? This must only show ONE 
>>>>>>>> value.
>>>>>>>> How you deduce that might be based on the availability of the 
>>>>>>>> feature
>>>>>>>> set. Or store the TS value in the drvdata and use that instead for
>>>>>>>> controlling CMB/DSB.
>>>>>>>
>>>>>>> Since both of CMB/DSB need to have "enable_ts" SysFs file, can I 
>>>>>>> separate them
>>>>>>
>>>>>> The question really is, do we need fine grained control. i.e.,
>>>>>>
>>>>>> enable TS for DSB but not for CMB or vice versa.
>>>>>>
>>>>>> I am not an expert on the usage scenario of the same. So, if 
>>>>>> you/Qcomm
>>>>>> thinks the users need separate, fine grained control for timestamp
>>>>>> for the DSB and CMB, then yes, follow your recommendation below.
>>>>>> i.e., tpdm.../dsb_patt/enable_ts
>>>>>>
>>>>>>> as "enable_dsb_ts" and "enable_cmb_ts"? The path will be like below.
>>>>>>>
>>>>>>> tpdm0/dsb_patt/enable_dsb_ts
>>>>>>
>>>>>> You don't need enable_dsb_ts. It could be "enable_ts"
>>>>>>
>>>>>>>
>>>>>>> tpdm1/cmb_patt/enable_cmb_ts
>>>>>>>
>>>>>>> Is this design appropriate?
>>>>>>
>>>>>>
>>>>>> Otherwise, stick to single enable_ts : which enables the ts for both
>>>>>> CMB/DSB. And it only ever show one value : 0 (TS is disabled for both
>>>>>> CMB/DSB) 1 : TS enabled for both.
>>>>>
>>>>> We have a very special case, such as the TPDM supporting both CMB and
>>>>>
>>>>> DSB datasets. Although this case is very rare, it still exists.
>>>>>
>>>>> Can I use the data bit to instruct whether timestamp is enabled for 
>>>>> CMB/DSB or not? For example,
>>>>>
>>>>> size = sysfs_emit(buf, "%u\n",
>>>>>                  (unsigned int)(drvdata->dsb->patt_ts << 1 | 
>>>>> drvdata->cmb->patt_ts));
>>>>>
>>>>> Thus, this value can instruct the following situations.
>>>>>
>>>>> 0 - TS is disabled for both CMB/DSB
>>>>>
>>>>> 1 - TS is enabled for CMB
>>>>>
>>>>> 2 - TS is enabled for DSB
>>>>>
>>>>> 3 - TS is enabled for both
>>>>>
>>>>> Is this approach acceptable?
>>>>>
>>>>
>>>> No, please stick to separate controls for TS. Do not complicate
>>>> the user interface.
>>>>
>>>> i.e.,
>>>> tpdm0/dsb_patt/enable_ts
>>>> tpdm0/cmb_patt/enable_ts
>>>
>>> We need to be able to control/show dsb and cmb timestamp enablement 
>>> independently.
>>>
>>> Can we achieve this requirement if we use a sysfs file with the same 
>>> name?
>>
>> They are independent and in their respective directory (group) for CMB 
>> and DSB. What am I missing ?
>> e.g., if you want to enable TS for DSB, you do :
>>
>> $ echo 1 > dsb_patt/enable_ts
>>
>> And that only works for DSB not for CMB.
> 
> We have a special case that the TPDM supports both DSB and CMB dataset. 
> In this special case, when we
> 
> issue this command to enable timestamp, it will call enable_ts_store 
> API, right?
> 
>      if (tpdm_has_dsb_dataset(drvdata))
>          drvdata->dsb->patt_ts = !!val;
> 
>      if (tpdm_has_cmb_dataset(drvdata))
>          drvdata->cmb->patt_ts = !!val;

I don't understand. If they both are under different subgroups, why
should they be conflicting ? Are you not able to distinguish them, when
  you creat those attributes ? i.e., create two different "attributes" ?

See below.

> Since this special TPDM supports both DSB and CMB dataset, both DSB 
> patt_ts and CMB patt_ts will be set
> 
> in this case even if I only configure the file in the DSB directory, right?
> 
> This is the problem we have now.
> 


>>>>>>>>
>>>>>>>>
>>>>>>>>> +
>>>>>>>>> +    return size;
>>>>>>>>>   }
>>>>>>>>>     /*
>>>>>>>>> @@ -715,8 +755,13 @@ static ssize_t enable_ts_store(struct 
>>>>>>>>> device *dev,
>>>>>>>>>           return -EINVAL;
>>>>>>>>>         spin_lock(&drvdata->spinlock);
>>>>>>>>> -    drvdata->dsb->patt_ts = !!val;
>>>>>>>>> +    if (tpdm_has_dsb_dataset(drvdata))
>>>>>>>>> +        drvdata->dsb->patt_ts = !!val;
>>>>>>>>> +
>>>>>>>>> +    if (tpdm_has_cmb_dataset(drvdata))
>>>>>>>>> +        drvdata->cmb->patt_ts = !!val;
>>>>>>>>>       spin_unlock(&drvdata->spinlock);
>>>>>>>>> +
>>>>>>>>>       return size;
>>>>>>>>>   }
>>>>>>>>>   static DEVICE_ATTR_RW(enable_ts);

Do not overload the same for both DSB and CMB. Create one for each in 
DSB and CMB ? They could share the same show/store routines, but could
be done with additional variable to indicate which attribute they are 
controlling. Like the other attributes, using dev_ext_attribute or such.


Suzuki

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