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 [off-list ref] wrote:

quoted

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 <redacted>
---
  .../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

quoted

  };

  struct etr_buf_operations {
--
2.34.1

regards

Mike