Re: [PATCH v3 RESEND 09/10] coresight: tmc: add read function for byte-cntr

Hi,

On Mon, 14 Jul 2025 at 07:32, Jie Gan jie.gan@oss.qualcomm.com wrote:

The byte-cntr read function always reads trace data from the deactivated and filled buffer which is already synced. The read function will fail when the ETR cannot find a available buffer to receive trace data.

The read function terminates when the path is disabled or interrupted by a signal.

Signed-off-by: Jie Gan jie.gan@oss.qualcomm.com

.../hwtracing/coresight/coresight-tmc-core.c | 31 ++++++- .../hwtracing/coresight/coresight-tmc-etr.c | 90 +++++++++++++++++++ drivers/hwtracing/coresight/coresight-tmc.h | 3 + 3 files changed, 120 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c index 354faeeddbb2..3ab25adc4e4d 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-core.c +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c @@ -318,14 +318,18 @@ static int tmc_open(struct inode *inode, struct file *file) return 0; }

-static ssize_t tmc_get_sysfs_trace(struct tmc_drvdata *drvdata, loff_t pos, size_t len,

•                              char **bufpp)
  

+static ssize_t tmc_get_sysfs_trace(struct tmc_drvdata *drvdata,

•                              struct ctcu_byte_cntr *byte_cntr_data,
  

•                              loff_t pos, size_t len, char **bufpp)
  

Don't change "core" functionalilty to add in bytecntr parameters.

Use helper functions to have a pattern such as:

if (bytecntr_active()) call_byte_cntr_fn() else call_standard_fn()

{ switch (drvdata->config_type) { case TMC_CONFIG_TYPE_ETB: case TMC_CONFIG_TYPE_ETF: return tmc_etb_get_sysfs_trace(drvdata, pos, len, bufpp); case TMC_CONFIG_TYPE_ETR:

•           if (byte_cntr_data && byte_cntr_data->thresh_val)
  

•                   return tmc_byte_cntr_get_data(drvdata, byte_cntr_data, len, bufpp);
  

•           return tmc_etr_get_sysfs_trace(drvdata, pos, len, bufpp);
    }
  
  

@@ -339,7 +343,21 @@ static ssize_t tmc_read(struct file *file, char __user *data, size_t len, ssize_t actual; struct tmc_drvdata *drvdata = container_of(file->private_data, struct tmc_drvdata, miscdev);

•   actual = tmc_get_sysfs_trace(drvdata, *ppos, len, &bufp);
  

•   struct coresight_device *helper = coresight_get_helper(drvdata->csdev,
  

•                                           CORESIGHT_DEV_SUBTYPE_HELPER_CTCU);
  

•   struct ctcu_byte_cntr *byte_cntr_data = NULL;
  

•   struct ctcu_drvdata *ctcu_drvdata = NULL;
  

•   int port;
  

•   if (helper) {
  

•           port = coresight_get_port_helper(drvdata->csdev, helper);
  

•           if (port >= 0) {
  

•                   ctcu_drvdata = dev_get_drvdata(helper->dev.parent);
  

•                   byte_cntr_data = &ctcu_drvdata->byte_cntr_data[port];
  

•           }
  

•   }
  

•   actual = tmc_get_sysfs_trace(drvdata, byte_cntr_data, *ppos, len, &bufp);
    if (actual <= 0)
            return 0;
  
  

@@ -349,7 +367,12 @@ static ssize_t tmc_read(struct file *file, char __user *data, size_t len, return -EFAULT; }

•   *ppos += actual;
  

•   if (byte_cntr_data && byte_cntr_data->thresh_val) {
  

•           byte_cntr_data->total_size += actual;
  

•           drvdata->reading_node->pos += actual;
  

•   } else
  

•           *ppos += actual;
  

•   dev_dbg(&drvdata->csdev->dev, "%zu bytes copied\n", actual);
  
    return actual;
  

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c index 3e3e1b5e78ca..174411e76047 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c @@ -1163,6 +1163,10 @@ ssize_t tmc_etr_get_sysfs_trace(struct tmc_drvdata *drvdata, ssize_t actual = len; struct etr_buf *etr_buf = drvdata->sysfs_buf;

•   /* Reading the buffer from the buf_node if it exists*/
  

•   if (drvdata->reading_node)
  

•           etr_buf = drvdata->reading_node->sysfs_buf;
  

•   if (pos + actual > etr_buf->len)
            actual = etr_buf->len - pos;
    if (actual <= 0)
  

@@ -1339,6 +1343,92 @@ static bool tmc_byte_cntr_switch_buffer(struct tmc_drvdata *drvdata, return found_free_buf; }

+/*

• • tmc_byte_cntr_get_data() - reads data from the deactivated and filled buffer.
• • The byte-cntr reading work reads data from the deactivated and filled buffer.
• • The read operation waits for a buffer to become available, either filled or
• • upon timeout, and then reads trace data from the synced buffer.
• */

This entire function should be moved to one of the byte-cntr source files.

+ssize_t tmc_byte_cntr_get_data(struct tmc_drvdata *drvdata,

•                          struct ctcu_byte_cntr *byte_cntr_data,
  

•                          size_t len, char **bufpp)
  

+{

•   size_t thresh_val = byte_cntr_data->thresh_val;
  

•   atomic_t *irq_cnt = &byte_cntr_data->irq_cnt;
  

•   struct etr_buf *sysfs_buf = drvdata->sysfs_buf;
  

•   struct device *dev = &drvdata->csdev->dev;
  

•   struct etr_buf_node *nd, *next;
  

•   ssize_t size = sysfs_buf->size;
  

•   ssize_t actual;
  

•   loff_t pos;
  

•   int ret;
  

+wait_buffer:

•   if (!byte_cntr_data->reading_buf) {
  

•           ret = wait_event_interruptible_timeout(byte_cntr_data->wq,
  

•                           ((atomic_read(irq_cnt) + 1) * thresh_val >= size) ||
  

•                           !byte_cntr_data->enable,
  

•                           BYTE_CNTR_TIMEOUT);
  

•           if (ret < 0)
  

•                   return ret;
  

•           /*
  

•            * The current etr_buf is almost full or timeout is triggered,
  

•            * so switch the buffer and mark the switched buffer as reading.
  

•            */
  

•           if (byte_cntr_data->enable) {
  

•                   if (!tmc_byte_cntr_switch_buffer(drvdata, byte_cntr_data)) {
  

•                           dev_err(dev, "Switch buffer failed for byte-cntr\n");
  

•                           return -EINVAL;
  

•                   }
  

•                   byte_cntr_data->reading_buf = true;
  

•           } else {
  

•                   if (!drvdata->reading_node) {
  

•                           list_for_each_entry_safe(nd, next, &drvdata->etr_buf_list, node) {
  

•                                   if (nd->sysfs_buf == sysfs_buf) {
  

•                                           nd->pos = 0;
  

•                                           drvdata->reading_node = nd;
  

•                                           break;
  

•                                   }
  

•                           }
  

•                   }
  

•                   pos = drvdata->reading_node->pos;
  

•                   actual = tmc_etr_get_sysfs_trace(drvdata, pos, len, bufpp);
  

•                   if (actual > 0)
  

•                           return actual;
  

•                   drvdata->reading_node = NULL;
  

•                   /* Exit byte-cntr reading */
  

•                   return -EINVAL;
  

•           }
  

•   }
  

•   /* Check the status of current etr_buf*/
  

•   if ((atomic_read(irq_cnt) + 1) * thresh_val >= size)
  

•           /*
  

•            * Unlikely to find a free buffer to switch, so just disable
  

•            * the ETR for a while.
  

•            */
  

•           if (!tmc_byte_cntr_switch_buffer(drvdata, byte_cntr_data))
  

•                   dev_info(dev, "No available buffer to store data, disable ETR\n");
  

•   pos = drvdata->reading_node->pos;
  

•   actual = tmc_etr_get_sysfs_trace(drvdata, pos, len, bufpp);
  

•   if (actual == 0) {
  

•           /* Reading work for marked buffer has finished, reset flags */
  

•           drvdata->reading_node->reading = false;
  

•           byte_cntr_data->reading_buf = false;
  

•           drvdata->reading_node = NULL;
  

•           /* Nothing in the buffer, wait for next buffer to be filled */
  

•           goto wait_buffer;
  

•   }
  

•   return actual;
  

+}

static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev) { int ret = 0; diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h index 1dbba0bc50a3..4136ec5ecaf7 100644 --- a/drivers/hwtracing/coresight/coresight-tmc.h +++ b/drivers/hwtracing/coresight/coresight-tmc.h @@ -364,6 +364,9 @@ int tmc_read_prepare_byte_cntr(struct tmc_drvdata *drvdata, struct ctcu_byte_cntr *byte_cntr_data); int tmc_read_unprepare_byte_cntr(struct tmc_drvdata *drvdata, struct ctcu_byte_cntr *byte_cntr_data);

Declare this in a byte_cntr header file, not here.

+ssize_t tmc_byte_cntr_get_data(struct tmc_drvdata *drvdata,

•                          struct ctcu_byte_cntr *byte_cntr_data,
  

•                          size_t len, char **bufpp);
  
  

#define TMC_REG_PAIR(name, lo_off, hi_off) \ static inline u64 \ -- 2.34.1