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

[Jie Gan]

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@xxxxxxxxxx>
> > Signed-off-by: Jie Gan <jie.gan@xxxxxxxxxxxxxxxx>
> > ---
> >   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