lkml.org 
[lkml]   [2018]   [Jul]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 6/6] coresight: etm-perf: Add support for ETR backend
Hi Suzuki,

On Wed, Jul 11, 2018 at 03:16:39PM +0100, Suzuki K Poulose wrote:
> Add support for using TMC-ETR as backend for ETM perf tracing.
> We use software double buffering at the moment. i.e, the TMC-ETR
> uses a separate buffer than the perf ring buffer. The data is
> copied to the perf ring buffer once a session completes.
>
> The TMC-ETR would try to match the larger of perf ring buffer
> or the ETR buffer size configured via sysfs, scaling down to
> a minimum limit of 1MB.
>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> drivers/hwtracing/coresight/coresight-tmc-etr.c | 265 +++++++++++++++++++++++-
> drivers/hwtracing/coresight/coresight-tmc.h | 2 +
> 2 files changed, 265 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 20a0beb..af921da 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -21,6 +21,28 @@ struct etr_flat_buf {
> };
>
> /*
> + * etr_perf_buffer - Perf buffer used for ETR
> + * @etr_buf - Actual buffer used by the ETR
> + * @snaphost - Perf session mode
> + * @head - handle->head at the beginning of the session.
> + * @nr_pages - Number of pages in the ring buffer.
> + * @pages - Array of Pages in the ring buffer.
> + */
> +struct etr_perf_buffer {
> + struct etr_buf *etr_buf;
> + bool snapshot;
> + unsigned long head;
> + int nr_pages;
> + void **pages;
> +};
> +
> +/* Convert the perf index to an offset within the ETR buffer */
> +#define PERF_IDX2OFF(idx, buf) ((idx) % ((buf)->nr_pages << PAGE_SHIFT))
> +
> +/* Lower limit for ETR hardware buffer */
> +#define TMC_ETR_PERF_MIN_BUF_SIZE SZ_1M
> +
> +/*
> * The TMC ETR SG has a page size of 4K. The SG table contains pointers
> * to 4KB buffers. However, the OS may use a PAGE_SIZE different from
> * 4K (i.e, 16KB or 64KB). This implies that a single OS page could
> @@ -1103,10 +1125,245 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev)
> return ret;
> }
>
> +/*
> + * tmc_etr_setup_perf_buf: Allocate ETR buffer for use by perf.
> + * The size of the hardware buffer is dependent on the size configured
> + * via sysfs and the perf ring buffer size. We prefer to allocate the
> + * largest possible size, scaling down the size by half until it
> + * reaches a minimum limit (1M), beyond which we give up.
> + */
> +static struct etr_perf_buffer *
> +tmc_etr_setup_perf_buf(struct tmc_drvdata *drvdata, int node, int nr_pages,
> + void **pages, bool snapshot)
> +{
> + struct etr_buf *etr_buf;
> + struct etr_perf_buffer *etr_perf;
> + unsigned long size;
> +
> + etr_perf = kzalloc_node(sizeof(*etr_perf), GFP_KERNEL, node);
> + if (!etr_perf)
> + return ERR_PTR(-ENOMEM);
> +
> + /*
> + * Try to match the perf ring buffer size if it is larger
> + * than the size requested via sysfs.
> + */
> + if ((nr_pages << PAGE_SHIFT) > drvdata->size) {
> + etr_buf = tmc_alloc_etr_buf(drvdata, (nr_pages << PAGE_SHIFT),
> + 0, node, NULL);
> + if (!IS_ERR(etr_buf))
> + goto done;
> + }
> +
> + /*
> + * Else switch to configured size for this ETR
> + * and scale down until we hit the minimum limit.
> + */
> + size = drvdata->size;
> + do {
> + etr_buf = tmc_alloc_etr_buf(drvdata, size, 0, node, NULL);
> + if (!IS_ERR(etr_buf))
> + goto done;
> + size /= 2;
> + } while (size >= TMC_ETR_PERF_MIN_BUF_SIZE);
> +
> + kfree(etr_perf);
> + return ERR_PTR(-ENOMEM);
> +
> +done:
> + etr_perf->etr_buf = etr_buf;
> + return etr_perf;
> +}
> +
> +
> +static void *tmc_etr_alloc_perf_buffer(struct coresight_device *csdev,
> + int cpu, void **pages, int nr_pages,
> + bool snapshot)
> +{
> + struct etr_perf_buffer *etr_perf;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> + if (cpu == -1)
> + cpu = smp_processor_id();
> +
> + etr_perf = tmc_etr_setup_perf_buf(drvdata, cpu_to_node(cpu),
> + nr_pages, pages, snapshot);
> + if (IS_ERR(etr_perf)) {
> + dev_dbg(drvdata->dev, "Unable to allocate ETR buffer\n");
> + return NULL;
> + }
> +
> + etr_perf->snapshot = snapshot;
> + etr_perf->nr_pages = nr_pages;
> + etr_perf->pages = pages;
> +
> + return etr_perf;
> +}
> +
> +static void tmc_etr_free_perf_buffer(void *config)
> +{
> + struct etr_perf_buffer *etr_perf = config;
> +
> + if (etr_perf->etr_buf)
> + tmc_free_etr_buf(etr_perf->etr_buf);
> + kfree(etr_perf);
> +}
> +
> +static int tmc_etr_set_perf_buffer(struct coresight_device *csdev,
> + struct perf_output_handle *handle,
> + void *config)
> +{
> + int rc = 0;
> + unsigned long flags;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> + struct etr_perf_buffer *etr_perf = config;
> +
> + etr_perf->head = handle->head;
> + spin_lock_irqsave(&drvdata->spinlock, flags);
> + if (WARN_ON(drvdata->perf_data))
> + rc = -EBUSY;
> + else
> + drvdata->perf_data = etr_perf;
> + spin_unlock_irqrestore(&drvdata->spinlock, flags);
> + return rc;
> +}
> +
> +/*
> + * tmc_etr_sync_perf_buffer: Copy the actual trace data from the hardware
> + * buffer to the perf ring buffer.
> + */
> +static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf)
> +{
> + long bytes, to_copy;
> + long pg_idx, pg_offset, src_offset;
> + unsigned long head = etr_perf->head;
> + char **dst_pages, *src_buf;
> + struct etr_buf *etr_buf = etr_perf->etr_buf;
> +
> + head = PERF_IDX2OFF(etr_perf->head, etr_perf);

I'm puzzled here. Since etr_perf->head is set in tmc_etr_set_perf_buffer() to
the value of handle->head, its value is always within the range of the perf ring
buffer. In tmc_etr_alloc_perf_buffer() etr_perf->nr_pages is set to the number
of pages present in that ring buffer. As such I'm not sure as to why we need
the PERF_IDX2OFF() macro.

It seems to me that "head = etr_perf->head;" above is sufficient.

> + pg_idx = head >> PAGE_SHIFT;
> + pg_offset = head & (PAGE_SIZE - 1);
> + dst_pages = (char **)etr_perf->pages;
> + src_offset = etr_buf->offset;
> + to_copy = etr_buf->len;
> +
> + while (to_copy > 0) {
> + /*
> + * We can copy minimum of :

s/We can copy minimum of :/In one iteration we can copy a minimum of:/

If I'm wrong about the PERF_IDX2OFF(), don't bother respinning just for that.

Thanks,
Mathieu

> + * 1) what is available in the source buffer,
> + * 2) what is available in the source buffer, before it
> + * wraps around.
> + * 3) what is available in the destination page.
> + * in one iteration.
> + */
> + bytes = tmc_etr_buf_get_data(etr_buf, src_offset, to_copy,
> + &src_buf);
> + if (WARN_ON_ONCE(bytes <= 0))
> + break;
> + bytes = min(bytes, (long)(PAGE_SIZE - pg_offset));
> +
> + memcpy(dst_pages[pg_idx] + pg_offset, src_buf, bytes);
> +
> + to_copy -= bytes;
> +
> + /* Move destination pointers */
> + pg_offset += bytes;
> + if (pg_offset == PAGE_SIZE) {
> + pg_offset = 0;
> + if (++pg_idx == etr_perf->nr_pages)
> + pg_idx = 0;
> + }
> +
> + /* Move source pointers */
> + src_offset += bytes;
> + if (src_offset >= etr_buf->size)
> + src_offset -= etr_buf->size;
> + }
> +}
> +
> +/*
> + * tmc_etr_update_perf_buffer : Update the perf ring buffer with the
> + * available trace data. We use software double buffering at the moment.
> + *
> + * TODO: Add support for reusing the perf ring buffer.
> + */
> +static unsigned long
> +tmc_etr_update_perf_buffer(struct coresight_device *csdev,
> + struct perf_output_handle *handle,
> + void *config)
> +{
> + bool lost = false;
> + unsigned long flags, size = 0;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> + struct etr_perf_buffer *etr_perf = config;
> + struct etr_buf *etr_buf = etr_perf->etr_buf;
> +
> + spin_lock_irqsave(&drvdata->spinlock, flags);
> + if (WARN_ON(drvdata->perf_data != etr_perf)) {
> + lost = true;
> + spin_unlock_irqrestore(&drvdata->spinlock, flags);
> + goto out;
> + }
> +
> + CS_UNLOCK(drvdata->base);
> +
> + tmc_flush_and_stop(drvdata);
> + tmc_sync_etr_buf(drvdata);
> +
> + CS_UNLOCK(drvdata->base);
> + /* Reset perf specific data */
> + drvdata->perf_data = NULL;
> + spin_unlock_irqrestore(&drvdata->spinlock, flags);
> +
> + size = etr_buf->len;
> + tmc_etr_sync_perf_buffer(etr_perf);
> +
> + /*
> + * Update handle->head in snapshot mode. Also update the size to the
> + * hardware buffer size if there was an overflow.
> + */
> + if (etr_perf->snapshot) {
> + handle->head += size;
> + if (etr_buf->full)
> + size = etr_buf->size;
> + }
> +
> + lost |= etr_buf->full;
> +out:
> + if (lost)
> + perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> + return size;
> +}
> +
> static int tmc_enable_etr_sink_perf(struct coresight_device *csdev)
> {
> - /* We don't support perf mode yet ! */
> - return -EINVAL;
> + int rc = 0;
> + unsigned long flags;
> + struct etr_perf_buffer *etr_perf;
> + struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
> +
> + spin_lock_irqsave(&drvdata->spinlock, flags);
> + /*
> + * There can be only one writer per sink in perf mode. If the sink
> + * is already open in SYSFS mode, we can't use it.
> + */
> + if (drvdata->mode != CS_MODE_DISABLED) {
> + rc = -EBUSY;
> + goto unlock_out;
> + }
> +
> + etr_perf = drvdata->perf_data;
> + if (WARN_ON(!etr_perf || !etr_perf->etr_buf)) {
> + rc = -EINVAL;
> + goto unlock_out;
> + }
> +
> + drvdata->mode = CS_MODE_PERF;
> + tmc_etr_enable_hw(drvdata, etr_perf->etr_buf);
> +
> +unlock_out:
> + spin_unlock_irqrestore(&drvdata->spinlock, flags);
> + return rc;
> }
>
> static int tmc_enable_etr_sink(struct coresight_device *csdev, u32 mode)
> @@ -1147,6 +1404,10 @@ static void tmc_disable_etr_sink(struct coresight_device *csdev)
> static const struct coresight_ops_sink tmc_etr_sink_ops = {
> .enable = tmc_enable_etr_sink,
> .disable = tmc_disable_etr_sink,
> + .alloc_buffer = tmc_etr_alloc_perf_buffer,
> + .update_buffer = tmc_etr_update_perf_buffer,
> + .set_buffer = tmc_etr_set_perf_buffer,
> + .free_buffer = tmc_etr_free_perf_buffer,
> };
>
> const struct coresight_ops tmc_etr_cs_ops = {
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index 872f63e..487c537 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -170,6 +170,7 @@ struct etr_buf {
> * @trigger_cntr: amount of words to store after a trigger.
> * @etr_caps: Bitmask of capabilities of the TMC ETR, inferred from the
> * device configuration register (DEVID)
> + * @perf_data: PERF buffer for ETR.
> * @sysfs_data: SYSFS buffer for ETR.
> */
> struct tmc_drvdata {
> @@ -191,6 +192,7 @@ struct tmc_drvdata {
> u32 trigger_cntr;
> u32 etr_caps;
> struct etr_buf *sysfs_buf;
> + void *perf_data;
> };
>
> struct etr_buf_operations {
> --
> 2.7.4
>
\
 
 \ /
  Last update: 2018-07-15 22:06    [W:0.096 / U:19.948 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site