Re: [PATCH V2 1/6] coresight: etb10: Properly set AUX buffer head in snapshot mode

Good day Suzuki,

On Wed, 15 May 2019 at 03:45, Suzuki K Poulose suzuki.poulose@arm.com wrote:

Hi Mathieu,

On 14/05/2019 20:40, Mathieu Poirier wrote:

...

Unify amongst sink drivers how the AUX ring buffer head is communicated to user space. That way the same algorithm in cs_etm_find_snapshot()

I would leave the userspace tool's function name out of the commit description and the comment below. We could instead say: "That way the same algorithm can be used by the userspace tool to determine the position and the size of the latest snapshot data."

I purposely added the name of the function there so that people can quickly find it and avoid any misunderstanding about the code in question. But I also have the same information as a comment in the code, which should be sufficient. I'll fix it.

...

can be used to determine where the latest data is and how much of it to access.

Signed-off-by: Mathieu Poirier mathieu.poirier@linaro.org

drivers/hwtracing/coresight/coresight-etb10.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c index 4ee4c80a4354..60e753b1768d 100644 --- a/drivers/hwtracing/coresight/coresight-etb10.c +++ b/drivers/hwtracing/coresight/coresight-etb10.c @@ -548,13 +548,14 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev, writel_relaxed(0x0, drvdata->base + ETB_RAM_WRITE_POINTER);

  /*

•  * In snapshot mode we have to update the handle->head to point
  

•  * to the new location.
  

•  * In snapshot mode we simply increment the head by the number of byte
  

•  * that were written.  User space function  cs_etm_find_snapshot() will
  

•  * figure out how many bytes to get from the AUX buffer based on the
  

•  * position of the head.
   */
  

• if (buf->snapshot) {
  

•         handle->head = (cur * PAGE_SIZE) + offset;
  

•         to_read = buf->nr_pages << PAGE_SHIFT;
  

• }
  

• if (buf->snapshot)
  

•         handle->head += to_read;
  

• __etb_enable_hw(drvdata);
  CS_LOCK(drvdata->base);
  

  out:

Otherwise:

Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com

Is this for all the kernel space patches or just this one?