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Message-ID: <20180508194241.GC3389@xps15>
Date: Tue, 8 May 2018 13:42:41 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
mike.leach@...aro.org, robert.walker@....com, mark.rutland@....com,
will.deacon@....com, robin.murphy@....com, sudeep.holla@....com,
frowand.list@...il.com, robh@...nel.org, john.horley@....com
Subject: Re: [PATCH v2 26/27] coresight: perf: Remove reset_buffer call back
for sinks
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.
>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....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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