On Wed, 5 Sep 2018 at 01:56, Leo Yan leo.yan@linaro.org wrote:

When tmc driver updates ring buffer and detects the ETB RAM has a wrap around, in the head of ring buffer the first four words is filled trace data by reading out RRD register, but the driver simply discards the first four words and leave the memory to store the barrier packets with value 0x7fff,ffff. As result we get below data content in the buffer:

+--------+--------+--------+--------+--------+--------+--------+ | trace0 | trace1 | trace2 | trace3 | trace4 | trace5 | ... | | v | v | v | v | | | | | barrier| barrier| barrier| barrier| | | | +--------+--------+--------+--------+--------+--------+--------+

On the other hand, the ring buffer actually has enough space for saving both barrier packets and trace data from ETB RAM. Ideally we should save both barrier packets and complete trace data in the ETB RAM for the wrap around case. So below is the ideal data content we can get: the first four words are for barrier packets and then save trace data from reading the first word from RRD register.

+--------+--------+--------+--------+--------+--------+--------+ | barrier| barrier| barrier| barrier| trace0 | trace1 | ... | +--------+--------+--------+--------+--------+--------+--------+

To achieve this purpose, this patch introduces a variable 'barrier_sz' to present the barrier packets length is to be written into the ring buffer. There have two cases that we will lose trace data so need to insert the barrier packets between two discontinuous trace data block; the first one case is the ETB RAM is in full state, another case is the ring buffer has no enough space for trace data at this time.

We firstly need to reserve memory space in the ring buffer for barrier packets and the left memory space can be used to save trace data. This patch caps the value 'barrier_sz' so ensure barrier length is not longer than ring buffer and calculate the rest memory space for 'to_read' for trace data recording.

At the data saving stage, the patch firstly saves barrier packets without reading RRD register so that will not lose trace data; after that it will save trace data by accessing RRD register. At the end, the read data length is the sum value of barrier length 'barrier_sz' plus trace data length 'to_read'.

Cc: Mathieu Poirier mathieu.poirier@linaro.org Cc: Mike Leach mike.leach@linaro.org Signed-off-by: Leo Yan leo.yan@linaro.org

---

drivers/hwtracing/coresight/coresight-tmc-etf.c | 34 +++++++++++++++++-------- 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c index e310613..9c599c9 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c @@ -387,7 +387,7 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev, const u32 *barrier; u32 *buf_ptr; u64 read_ptr, write_ptr;

•   u32 status, to_read;
  

•   u32 status, to_read, barrier_sz = 0;
  

This doesn't apply on my next branch. Please rebase and send both patches again.

Mathieu

    unsigned long offset;
    struct cs_buffers *buf = sink_config;
    struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

@@ -419,11 +419,18 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev, }

    /*

•    * The TMC RAM buffer may be bigger than the space available in the
  

•    * perf ring buffer (handle->size).  If so advance the RRP so that we
  

•    * get the latest trace data.
  

•    * Drop some trace data when the TMC RAM buffer is full or bigger than
  

•    * perf ring buffer.  For this case the trace data is discontinuous
  

•    * thus need to inser barrier packets.
     */
  

•   if (to_read > handle->size) {
  

•   barrier_sz = CORESIGHT_BARRIER_PKT_SIZE;
  

•   /*
  

•    * The sum of trace data and inserted barriers may be bigger than the
  

•    * space available in the perf ring buffer (handle->size).  If so
  

•    * advance the RRP so that we get the latest trace data.
  

•    */
  

•   if (to_read + barrier_sz > handle->size) {
            u32 mask = 0;
  
            /*
  

@@ -445,11 +452,15 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev, break; }

•           /* Make sure barrier isn't out of bound */
  

•           barrier_sz = min_t(u32, barrier_sz, handle->size);
  

•           /*
  

•            * Make sure the new size is aligned in accordance with the
  

•            * Firstly reserve the memory for inserted barrier packets;
  

•            * make sure the new size is aligned in accordance with the
             * requirement explained above.
             */
  

•           to_read = handle->size & mask;
  

•           to_read = (handle->size - barrier_sz) & mask;
            /* Move the RAM read pointer up */
            read_ptr = (write_ptr + drvdata->size) - to_read;
            /* Make sure we are still within our limits */
  

@@ -468,13 +479,14 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev, barrier = barrier_pkt;

    /* for every byte to read */

•   for (i = 0; i < to_read; i += 4) {
  

•   for (i = 0; i < to_read + barrier_sz; i += 4) {
            buf_ptr = buf->data_pages[cur] + offset;
  

•           *buf_ptr = readl_relaxed(drvdata->base + TMC_RRD);
  
  

•           if (lost && *barrier) {
  

•           if (i < barrier_sz) {
                    *buf_ptr = *barrier;
                    barrier++;
  

•           } else {
  

•                   *buf_ptr = readl_relaxed(drvdata->base + TMC_RRD);
            }
  
            offset += 4;
  

@@ -495,7 +507,7 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev, if (buf->snapshot) local_set(&buf->data_size, (cur * PAGE_SIZE) + offset); else

•           local_add(to_read, &buf->data_size);
  

•           local_add(to_read + barrier_sz, &buf->data_size);
  
    CS_LOCK(drvdata->base);
  

}

2.7.4