linux-kernel - Re: [PATCH v4 03/10] coresight: tmc: add etr_buf_list to store allocated etr

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Message-ID: <ae3a482b-2b8c-4390-a950-f9612303003d@oss.qualcomm.com>
Date: Wed, 6 Aug 2025 08:32:35 +0800
From: Jie Gan <jie.gan@....qualcomm.com>
To: Mike Leach <mike.leach@...aro.org>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
        James Clark <james.clark@...aro.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
        Jinlong Mao <jinlong.mao@....qualcomm.com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        Jie Gan <quic_jiegan@...cinc.com>
Subject: Re: [PATCH v4 03/10] coresight: tmc: add etr_buf_list to store
 allocated etr_buf



On 8/5/2025 6:15 PM, Mike Leach wrote:
> Hi
> 
> On Fri, 25 Jul 2025 at 11:08, Jie Gan <jie.gan@....qualcomm.com> wrote:
>>
>> Add a list to store allocated etr_buf.
>>
>> The byte-cntr functionality requires two etr_buf to receive trace data.
>> The active etr_buf collects the trace data from source device, while the
>> byte-cntr reading function accesses the deactivated etr_buf after is
>> has been filled and synced, transferring data to the userspace.
>>
>> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
>> ---
>>   .../hwtracing/coresight/coresight-tmc-core.c  |  1 +
>>   drivers/hwtracing/coresight/coresight-tmc.h   | 19 +++++++++++++++++++
>>   2 files changed, 20 insertions(+)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> index be964656be93..4d249af93097 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> @@ -830,6 +830,7 @@ static int __tmc_probe(struct device *dev, struct resource *res)
>>                  idr_init(&drvdata->idr);
>>                  mutex_init(&drvdata->idr_mutex);
>>                  dev_list = &etr_devs;
>> +               INIT_LIST_HEAD(&drvdata->etr_buf_list);
>>                  break;
>>          case TMC_CONFIG_TYPE_ETF:
>>                  desc.groups = coresight_etf_groups;
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
>> index 6541a27a018e..52ee5f8efe8c 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc.h
>> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
>> @@ -208,6 +208,21 @@ struct tmc_resrv_buf {
>>          s64             len;
>>   };
>>
>> +/**
>> + * @sysfs_buf: Allocated sysfs_buf.
>> + * @is_free:   Indicates whether the buffer is free to choose.
>> + * @reading:   Indicates whether the buffer is reading.
>> + * @pos:       Position of the buffer.
>> + * @node:      Node in etr_buf_list.
>> + */
>> +struct etr_buf_node {
>> +       struct etr_buf          *sysfs_buf;
>> +       bool                    is_free;
>> +       bool                    reading;
>> +       loff_t                  pos;
>> +       struct list_head        node;
>> +};
>> +
>>   /**
>>    * struct tmc_drvdata - specifics associated to an TMC component
>>    * @pclk:      APB clock if present, otherwise NULL
>> @@ -242,6 +257,8 @@ struct tmc_resrv_buf {
>>    *             (after crash) by default.
>>    * @crash_mdata: Reserved memory for storing tmc crash metadata.
>>    *              Used by ETR/ETF.
>> + * @etr_buf_list: List that is used to manage allocated etr_buf.
>> + * @reading_node: Available buffer for byte-cntr reading.
>>    */
>>   struct tmc_drvdata {
>>          struct clk              *pclk;
>> @@ -271,6 +288,8 @@ struct tmc_drvdata {
>>          struct etr_buf          *perf_buf;
>>          struct tmc_resrv_buf    resrv_buf;
>>          struct tmc_resrv_buf    crash_mdata;
>> +       struct list_head        etr_buf_list;
>> +       struct etr_buf_node     *reading_node;
> 
> Potential simplification:-
> do you need both reading_node here and reading in the etr_buf_node?
> reading_node handles the logic for which buffer is being read, while
> is_free handles the empty/full logic - reading seems unneeded?

Yes, you are right. I checked the usage of reading. It can be replaced 
by reading_node in switch function.

I will simplify this patch in next version.

Thanks,
Jie

> 
>>   };
>>
>>   struct etr_buf_operations {
>> --
>> 2.34.1
>>
> 
> regards
> 
> Mike
>