linux-kernel - Re: [PATCH 3/9] coresight-tpdm: Initialize DSB subunit configuration

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Message-ID: <23503d33-2761-50b5-91dd-4138494e54d5@arm.com>
Date:   Wed, 26 Oct 2022 15:18:47 +0100
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>
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,
        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@...aro.org
Subject: Re: [PATCH 3/9] coresight-tpdm: Initialize DSB subunit configuration

On 26/10/2022 09:10, Tao Zhang wrote:
> Hi Suzuki,
> 
> 在 10/24/2022 6:02 PM, Suzuki K Poulose 写道:
>> Hi
>>
>> On 08/09/2022 09:44, Tao Zhang wrote:
>>> DSB subunit need to be configured in enablement and disablement.
>>> A struct that specifics associated to dsb dataset is needed. It
>>> saves the configuration and parameters of the dsb datasets. This
>>> change is to add this struct and initialize the configuration of
>>> DSB subunit.
>>>
>>> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
>>> ---
>>>   drivers/hwtracing/coresight/coresight-tpdm.c | 44 
>>> ++++++++++++++++++++++++++--
>>>   drivers/hwtracing/coresight/coresight-tpdm.h | 17 +++++++++++
>>>   2 files changed, 58 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-tpdm.c 
>>> b/drivers/hwtracing/coresight/coresight-tpdm.c
>>> index 88df3e6..69ea453 100644
>>> --- a/drivers/hwtracing/coresight/coresight-tpdm.c
>>> +++ b/drivers/hwtracing/coresight/coresight-tpdm.c
>>> @@ -24,6 +24,22 @@ static void tpdm_enable_dsb(struct tpdm_drvdata 
>>> *drvdata)
>>>   {
>>>       u32 val;
>>>   +    val = readl_relaxed(drvdata->base + TPDM_DSB_TIER);
>>> +    /* Set trigger timestamp */
>>> +    if (drvdata->dsb->trig_ts)
>>
>> What happens if this instance doesn't have a DSB set ? Have
>> you tested this on a system without the DSB ?
>>
> The function "tpdm_enable_dsb" will only be called when it is checked 
> that the DSB dataset is present.
> 
> And only the TPDM that supports the DSB dataset will have the DSB TIER 
> register.
> 
> If the TPDM doesn't support the DSB dataset, this instance should not be 
> run. Otherwise, it will cause that the incorrect register is accessed.

Thanks, this is what happens when you send something that is not queued
anywhwere. Please provide a reference tree in the future, for ease of
reviewing such things

Suzuki