Re: [PATCH v2 26/27] coresight: perf: Remove reset_buffer call back for sinks

[Suzuki K Poulose]

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@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> >   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