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

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

On 7/22/2025 11:01 PM, Mike Leach wrote:
> 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()

got it. Will fix in next version.

Thanks,
Jie

> 
>>   {
>>          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.

I will add it to,for example, ctcu_byte_cntr_read_ops->read.
So I think I dont need define it in any header file in future.
Will remove it.

Thanks,
Jie

> 
>> +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
>>
> 
>