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Subject[PATCH 6/6] coresight: etm-perf: Add support for ETR backend
Date
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);
+ 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 :
+ * 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
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