linux-kernel - Re: [PATCH v4 04/10] coresight: tmc: add create/delete functions for etr_buf

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Message-ID: <CAJ9a7VgOTfDHG+nrEUQ5+fxrcCd+ZaWWnxt_F8kavbHP38QCVw@mail.gmail.com>
Date: Tue, 5 Aug 2025 11:27:46 +0100
From: Mike Leach <mike.leach@...aro.org>
To: Jie Gan <jie.gan@....qualcomm.com>
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 04/10] coresight: tmc: add create/delete functions for etr_buf_node

Hi,

On Fri, 25 Jul 2025 at 11:08, Jie Gan <jie.gan@....qualcomm.com> wrote:
>
> Create and insert or remove the etr_buf_node to/from the etr_buf_list.
>
> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
> ---
>  .../hwtracing/coresight/coresight-tmc-etr.c   | 65 +++++++++++++++++++
>  drivers/hwtracing/coresight/coresight-tmc.h   |  2 +
>  2 files changed, 67 insertions(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index b07fcdb3fe1a..e8ecb3e087ab 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -1909,6 +1909,71 @@ 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)
> +{
> +       struct etr_buf_node *nd, *next;
> +
> +       list_for_each_entry_safe(nd, next, &drvdata->etr_buf_list, node) {
> +               if (nd->sysfs_buf == drvdata->sysfs_buf) {
> +                       list_del(&nd->node);
> +                       kfree(nd);
> +               } else {
> +                       /* Free allocated buffers which are not utilized by ETR */
> +                       list_del(&nd->node);
> +                       tmc_free_etr_buf(nd->sysfs_buf);
> +                       nd->sysfs_buf = NULL;
> +                       kfree(nd);
> +               }
> +       }
> +}
> +EXPORT_SYMBOL_GPL(tmc_clean_etr_buf_list);
> +
> +/**
> + * tmc_create_etr_buf_node - create a node to store the alloc_buf and
> + * insert the node to the etr_buf_list. Create a new buffer if the
> + * alloc_buf is NULL.
> + * @drvdata:   driver data of the TMC device.
> + * @alloc_buf: the buffer that is inserted to the list.
> + *
> + * Return 0 upon success and return the error number if fail.
> + */
> +int tmc_create_etr_buf_node(struct tmc_drvdata *drvdata, struct etr_buf *alloc_buf)

This list handle function pair look a little asymmetric. Is it not
possible to change this to tmc_create_etr_buf_list(struct tmc_drvdata
*drvdata, int num_nodes)
so that one function creates all the nodes, and another destroys them.

In the logic that decides between using multi buffer or single buffer
you can then use  a construct such as:

if (single_buffer)
      drvdata->sysfs_buf = <alloc sysfs buffer>
else {
     tmc_create_etr_buf_list(drvdata, 2);
     <switch in avail buffer to drvdata->sysfs_buf
}

> +{
> +       struct etr_buf_node *sysfs_buf_node;
> +       struct etr_buf *sysfs_buf;
> +
> +       if (!alloc_buf) {
> +               sysfs_buf = tmc_alloc_etr_buf(drvdata, drvdata->size, 0, cpu_to_node(0), NULL);
> +               if (IS_ERR(sysfs_buf))
> +                       return PTR_ERR(sysfs_buf);
> +       } else
> +               sysfs_buf = alloc_buf;
> +
> +       sysfs_buf_node = kzalloc(sizeof(struct etr_buf_node), GFP_KERNEL);
> +       if (IS_ERR(sysfs_buf_node)) {
> +               if (!alloc_buf)
> +                       tmc_free_etr_buf(sysfs_buf);
> +               return PTR_ERR(sysfs_buf_node);
> +       }
> +
> +       sysfs_buf_node->sysfs_buf = sysfs_buf;
> +       sysfs_buf_node->reading = false;
> +       if (!alloc_buf)
> +               sysfs_buf_node->is_free = true;
> +       else
> +               sysfs_buf_node->is_free = false;
> +       list_add(&sysfs_buf_node->node, &drvdata->etr_buf_list);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(tmc_create_etr_buf_node);
> +
>  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 52ee5f8efe8c..3cb8ba9f88f5 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -461,5 +461,7 @@ void tmc_etr_remove_catu_ops(void);
>  struct etr_buf *tmc_etr_get_buffer(struct coresight_device *csdev,
>                                    enum cs_mode mode, void *data);
>  extern const struct attribute_group coresight_etr_group;
> +void tmc_clean_etr_buf_list(struct tmc_drvdata *drvdata);
> +int tmc_create_etr_buf_node(struct tmc_drvdata *drvdata, struct etr_buf *alloc_buf);
>
>  #endif
> --
> 2.34.1
>

Regards

Mike
-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK