Re: [PATCH v14 2/7] coresight: tmc: add create/clean functions for etr_buf_list

[Jie Gan <jie.gan@oss.qualcomm.com>]

On 3/9/2026 6:02 PM, Suzuki K Poulose wrote:
> On 09/03/2026 09:47, Jie Gan wrote:
>> Introduce functions for creating and inserting or removing the
>> etr_buf_node to/from the etr_buf_list.
>>
>> 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.
>>
>> Reviewed-by: Mike Leach <mike.leach@linaro.org>
>> Signed-off-by: Jie Gan <jie.gan@oss.qualcomm.com>
>> ---
>>   drivers/hwtracing/coresight/coresight-tmc-core.c |  1 +
>>   drivers/hwtracing/coresight/coresight-tmc-etr.c  | 94 ++++++++++++++ 
>> ++++++++++
>>   drivers/hwtracing/coresight/coresight-tmc.h      | 17 +++++
>>   3 files changed, 112 insertions(+)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/ 
>> drivers/hwtracing/coresight/coresight-tmc-core.c
>> index c89fe996af23..bac3278ef4dd 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> @@ -835,6 +835,7 @@ static int __tmc_probe(struct device *dev, struct 
>> resource *res)
>>           idr_init(&drvdata->idr);
>>           mutex_init(&drvdata->idr_mutex);
>>           dev_list = "tmc_etr";
>> +        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-etr.c b/ 
>> drivers/hwtracing/coresight/coresight-tmc-etr.c
>> index 4dc1defe27a5..15c0874ff641 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> @@ -1918,6 +1918,100 @@ const struct coresight_ops tmc_etr_cs_ops = {
>>       .panic_ops    = &tmc_etr_sync_ops,
>>   };
>> +/**
>> + * tmc_clean_etr_buf_list - clean the etr_buf_list.
>> + * @drvdata:    driver data of the TMC device.
>> + *
>> + * Remove the allocated node from the list and free the extra buffer.
>> + */
>> +void tmc_clean_etr_buf_list(struct tmc_drvdata *drvdata)
>> +{
> ...
> 
>> +}
>> +EXPORT_SYMBOL_GPL(tmc_clean_etr_buf_list);
>> +
>> +/**
>> + * tmc_create_etr_buf_list - create a list to manage the etr_buf_node.
>> + * @drvdata:    driver data of the TMC device.
>> + * @num_nodes:    number of nodes want to create with the list.
>> + *
>> + * Return 0 upon success and return the error number if fail.
>> + */
>> +int tmc_create_etr_buf_list(struct tmc_drvdata *drvdata, int num_nodes)
>> +{
> 
> ...
> 
> 
>> +EXPORT_SYMBOL_GPL(tmc_create_etr_buf_list);
> 
> Given the above functions are "EXPORTED" please could you make sure that
> the locking requirements are documented and asserted (lockdep_assert)
> in the functions ?
> 

Will checking the locking scenario here and asserted with 
lockdep_assert_held.

These two functions should be protected with tmc_drvdata->spinlock.

Thanks,
Jie

> 
> Suzuki
> 
> 
>> +
>>   int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
>>   {
>>       int ret = 0;
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/ 
>> hwtracing/coresight/coresight-tmc.h
>> index 319a354ede9f..5ac07e8dd5ff 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc.h
>> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
>> @@ -208,6 +208,19 @@ struct tmc_resrv_buf {
>>       s64        len;
>>   };
>> +/**
>> + * @sysfs_buf:    Allocated sysfs_buf.
>> + * @is_free:    Indicates whether the buffer is free to choose.
>> + * @pos:    Position of the buffer.
>> + * @node:    Node in etr_buf_list.
>> + */
>> +struct etr_buf_node {
>> +    struct etr_buf        *sysfs_buf;
>> +    bool            is_free;
>> +    loff_t            pos;
>> +    struct list_head    node;
>> +};
>> +
>>   /**
>>    * struct tmc_drvdata - specifics associated to an TMC component
>>    * @atclk:    optional clock for the core parts of the TMC.
>> @@ -245,6 +258,7 @@ 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.
>>    */
>>   struct tmc_drvdata {
>>       struct clk        *atclk;
>> @@ -275,6 +289,7 @@ 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_operations {
>> @@ -447,5 +462,7 @@ struct etr_buf *tmc_etr_get_buffer(struct 
>> coresight_device *csdev,
>>                      enum cs_mode mode,
>>                      struct coresight_path *path);
>>   extern const struct attribute_group coresight_etr_group;
>> +void tmc_clean_etr_buf_list(struct tmc_drvdata *drvdata);
>> +int tmc_create_etr_buf_list(struct tmc_drvdata *drvdata, int num_nodes);
>>   #endif
>>
> 
>