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SubjectRe: [PATCH v2 26/27] coresight: perf: Remove reset_buffer call back for sinks
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On 08/05/18 20:42, Mathieu Poirier wrote:
> On Tue, May 01, 2018 at 10:10:56AM +0100, Suzuki K Poulose wrote:
>> Right now we issue an update_buffer() and reset_buffer() call backs
>> in succession when we stop tracing an event. The update_buffer is
>> supposed to check the status of the buffer and make sure the ring buffer
>> is updated with the trace data. And we store information about the
>> size of the data collected only to be consumed by the reset_buffer
>> callback which always follows the update_buffer. This was originally
>> designed for handling future IPs which could trigger a buffer overflow
>> interrupt. This patch gets rid of the reset_buffer callback altogether
>> and performs the actions in update_buffer, making it return the size
>> collected. We can always add the support for handling the overflow
>> interrupt case later.
>>
>> This removes some not-so pretty hack (storing the new head in the
>> size field for snapshot mode) and cleans it up a little bit.
>
> IPs with an overflow interrupts will be arriving shortly, so it is not like the
> future is uncertain - they are coming. Right now the logic is there - I don't
> see a real need to consolidate things only to split it again in the near future.
>
> I agree the part about overloading buf->data_size with the head of the ring
> buffer when operating in snapshot mode isn't pretty (though well documented).
> If anything that can be improve, i.e add a buf->head and things will be clear.
> Once again this could be part of another patchset.
>

Mathieu,

I am not sure how was this supposed to be used in conjunction with the overflow
handling. Please could you help me here ? I might be able to retain
the callback and possibly improve it with the changes for etr_buf infrastructure.

Cheers
Suzuki


>>
>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> ---
>> drivers/hwtracing/coresight/coresight-etb10.c | 56 +++++------------------
>> drivers/hwtracing/coresight/coresight-etm-perf.c | 9 +---
>> drivers/hwtracing/coresight/coresight-tmc-etf.c | 58 +++++-------------------
>> include/linux/coresight.h | 5 +-
>> 4 files changed, 26 insertions(+), 102 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
>> index d9c2f87..b13712a 100644
>> --- a/drivers/hwtracing/coresight/coresight-etb10.c
>> +++ b/drivers/hwtracing/coresight/coresight-etb10.c
>> @@ -322,37 +322,7 @@ static int etb_set_buffer(struct coresight_device *csdev,
>> return ret;
>> }
>>
>> -static unsigned long etb_reset_buffer(struct coresight_device *csdev,
>> - struct perf_output_handle *handle,
>> - void *sink_config)
>> -{
>> - unsigned long size = 0;
>> - struct cs_buffers *buf = sink_config;
>> -
>> - if (buf) {
>> - /*
>> - * In snapshot mode ->data_size holds the new address of the
>> - * ring buffer's head. The size itself is the whole address
>> - * range since we want the latest information.
>> - */
>> - if (buf->snapshot)
>> - handle->head = local_xchg(&buf->data_size,
>> - buf->nr_pages << PAGE_SHIFT);
>> -
>> - /*
>> - * Tell the tracer PMU how much we got in this run and if
>> - * something went wrong along the way. Nobody else can use
>> - * this cs_buffers instance until we are done. As such
>> - * resetting parameters here and squaring off with the ring
>> - * buffer API in the tracer PMU is fine.
>> - */
>> - size = local_xchg(&buf->data_size, 0);
>> - }
>> -
>> - return size;
>> -}
>> -
>> -static void etb_update_buffer(struct coresight_device *csdev,
>> +static unsigned long etb_update_buffer(struct coresight_device *csdev,
>> struct perf_output_handle *handle,
>> void *sink_config)
>> {
>> @@ -361,13 +331,13 @@ static void etb_update_buffer(struct coresight_device *csdev,
>> u8 *buf_ptr;
>> const u32 *barrier;
>> u32 read_ptr, write_ptr, capacity;
>> - u32 status, read_data, to_read;
>> - unsigned long offset;
>> + u32 status, read_data;
>> + unsigned long offset, to_read;
>> struct cs_buffers *buf = sink_config;
>> struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>>
>> if (!buf)
>> - return;
>> + return 0;
>>
>> capacity = drvdata->buffer_depth * ETB_FRAME_SIZE_WORDS;
>>
>> @@ -472,18 +442,17 @@ static void etb_update_buffer(struct coresight_device *csdev,
>> writel_relaxed(0x0, drvdata->base + ETB_RAM_WRITE_POINTER);
>>
>> /*
>> - * In snapshot mode all we have to do is communicate to
>> - * perf_aux_output_end() the address of the current head. In full
>> - * trace mode the same function expects a size to move rb->aux_head
>> - * forward.
>> + * In snapshot mode we have to update the handle->head to point
>> + * to the new location.
>> */
>> - if (buf->snapshot)
>> - local_set(&buf->data_size, (cur * PAGE_SIZE) + offset);
>> - else
>> - local_add(to_read, &buf->data_size);
>> -
>> + if (buf->snapshot) {
>> + handle->head = (cur * PAGE_SIZE) + offset;
>> + to_read = buf->nr_pages << PAGE_SHIFT;
>> + }
>> etb_enable_hw(drvdata);
>> CS_LOCK(drvdata->base);
>> +
>> + return to_read;
>> }
>>
>> static const struct coresight_ops_sink etb_sink_ops = {
>> @@ -492,7 +461,6 @@ static const struct coresight_ops_sink etb_sink_ops = {
>> .alloc_buffer = etb_alloc_buffer,
>> .free_buffer = etb_free_buffer,
>> .set_buffer = etb_set_buffer,
>> - .reset_buffer = etb_reset_buffer,
>> .update_buffer = etb_update_buffer,
>> };
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
>> index 4e5ed65..5096def 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
>> @@ -342,15 +342,8 @@ static void etm_event_stop(struct perf_event *event, int mode)
>> if (!sink_ops(sink)->update_buffer)
>> return;
>>
>> - sink_ops(sink)->update_buffer(sink, handle,
>> + size = sink_ops(sink)->update_buffer(sink, handle,
>> event_data->snk_config);
>> -
>> - if (!sink_ops(sink)->reset_buffer)
>> - return;
>> -
>> - size = sink_ops(sink)->reset_buffer(sink, handle,
>> - event_data->snk_config);
>> -
>> perf_aux_output_end(handle, size);
>> }
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> index 0a32734..75ef5c4 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> @@ -360,36 +360,7 @@ static int tmc_set_etf_buffer(struct coresight_device *csdev,
>> return ret;
>> }
>>
>> -static unsigned long tmc_reset_etf_buffer(struct coresight_device *csdev,
>> - struct perf_output_handle *handle,
>> - void *sink_config)
>> -{
>> - long size = 0;
>> - struct cs_buffers *buf = sink_config;
>> -
>> - if (buf) {
>> - /*
>> - * In snapshot mode ->data_size holds the new address of the
>> - * ring buffer's head. The size itself is the whole address
>> - * range since we want the latest information.
>> - */
>> - if (buf->snapshot)
>> - handle->head = local_xchg(&buf->data_size,
>> - buf->nr_pages << PAGE_SHIFT);
>> - /*
>> - * Tell the tracer PMU how much we got in this run and if
>> - * something went wrong along the way. Nobody else can use
>> - * this cs_buffers instance until we are done. As such
>> - * resetting parameters here and squaring off with the ring
>> - * buffer API in the tracer PMU is fine.
>> - */
>> - size = local_xchg(&buf->data_size, 0);
>> - }
>> -
>> - return size;
>> -}
>> -
>> -static void tmc_update_etf_buffer(struct coresight_device *csdev,
>> +static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
>> struct perf_output_handle *handle,
>> void *sink_config)
>> {
>> @@ -398,17 +369,17 @@ 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;
>> - unsigned long offset;
>> + u32 status;
>> + unsigned long offset, to_read;
>> struct cs_buffers *buf = sink_config;
>> struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>>
>> if (!buf)
>> - return;
>> + return 0;
>>
>> /* This shouldn't happen */
>> if (WARN_ON_ONCE(drvdata->mode != CS_MODE_PERF))
>> - return;
>> + return 0;
>>
>> CS_UNLOCK(drvdata->base);
>>
>> @@ -497,18 +468,14 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev,
>> }
>> }
>>
>> - /*
>> - * In snapshot mode all we have to do is communicate to
>> - * perf_aux_output_end() the address of the current head. In full
>> - * trace mode the same function expects a size to move rb->aux_head
>> - * forward.
>> - */
>> - if (buf->snapshot)
>> - local_set(&buf->data_size, (cur * PAGE_SIZE) + offset);
>> - else
>> - local_add(to_read, &buf->data_size);
>> -
>> + /* In snapshot mode we have to update the head */
>> + if (buf->snapshot) {
>> + handle->head = (cur * PAGE_SIZE) + offset;
>> + to_read = buf->nr_pages << PAGE_SHIFT;
>> + }
>> CS_LOCK(drvdata->base);
>> +
>> + return to_read;
>> }
>>
>> static const struct coresight_ops_sink tmc_etf_sink_ops = {
>> @@ -517,7 +484,6 @@ static const struct coresight_ops_sink tmc_etf_sink_ops = {
>> .alloc_buffer = tmc_alloc_etf_buffer,
>> .free_buffer = tmc_free_etf_buffer,
>> .set_buffer = tmc_set_etf_buffer,
>> - .reset_buffer = tmc_reset_etf_buffer,
>> .update_buffer = tmc_update_etf_buffer,
>> };
>>
>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>> index c0e1568..41b3729 100644
>> --- a/include/linux/coresight.h
>> +++ b/include/linux/coresight.h
>> @@ -212,10 +212,7 @@ struct coresight_ops_sink {
>> int (*set_buffer)(struct coresight_device *csdev,
>> struct perf_output_handle *handle,
>> void *sink_config);
>> - unsigned long (*reset_buffer)(struct coresight_device *csdev,
>> - struct perf_output_handle *handle,
>> - void *sink_config);
>> - void (*update_buffer)(struct coresight_device *csdev,
>> + unsigned long (*update_buffer)(struct coresight_device *csdev,
>> struct perf_output_handle *handle,
>> void *sink_config);
>> };
>> --
>> 2.7.4
>>

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