static unsigned long tmc_update_etf_buffer()

in coresight/coresight-tmc-etf.c [444:565]

• 66 lines of code
• 15 McCabe index (conditional complexity)

static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev,
				  struct perf_output_handle *handle,
				  void *sink_config)
{
	bool lost = false;
	int i, cur;
	const u32 *barrier;
	u32 *buf_ptr;
	u64 read_ptr, write_ptr;
	u32 status;
	unsigned long offset, to_read = 0, flags;
	struct cs_buffers *buf = sink_config;
	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);

	if (!buf)
		return 0;

	/* This shouldn't happen */
	if (WARN_ON_ONCE(drvdata->mode != CS_MODE_PERF))
		return 0;

	spin_lock_irqsave(&drvdata->spinlock, flags);

	/* Don't do anything if another tracer is using this sink */
	if (atomic_read(csdev->refcnt) != 1)
		goto out;

	CS_UNLOCK(drvdata->base);

	tmc_flush_and_stop(drvdata);

	read_ptr = tmc_read_rrp(drvdata);
	write_ptr = tmc_read_rwp(drvdata);

	/*
	 * Get a hold of the status register and see if a wrap around
	 * has occurred.  If so adjust things accordingly.
	 */
	status = readl_relaxed(drvdata->base + TMC_STS);
	if (status & TMC_STS_FULL) {
		lost = true;
		to_read = drvdata->size;
	} else {
		to_read = CIRC_CNT(write_ptr, read_ptr, drvdata->size);
	}

	/*
	 * The TMC RAM buffer may be bigger than the space available in the
	 * perf ring buffer (handle->size).  If so advance the RRP so that we
	 * get the latest trace data.  In snapshot mode none of that matters
	 * since we are expected to clobber stale data in favour of the latest
	 * traces.
	 */
	if (!buf->snapshot && to_read > handle->size) {
		u32 mask = tmc_get_memwidth_mask(drvdata);

		/*
		 * Make sure the new size is aligned in accordance with the
		 * requirement explained in function tmc_get_memwidth_mask().
		 */
		to_read = handle->size & mask;
		/* Move the RAM read pointer up */
		read_ptr = (write_ptr + drvdata->size) - to_read;
		/* Make sure we are still within our limits */
		if (read_ptr > (drvdata->size - 1))
			read_ptr -= drvdata->size;
		/* Tell the HW */
		tmc_write_rrp(drvdata, read_ptr);
		lost = true;
	}

	/*
	 * Don't set the TRUNCATED flag in snapshot mode because 1) the
	 * captured buffer is expected to be truncated and 2) a full buffer
	 * prevents the event from being re-enabled by the perf core,
	 * resulting in stale data being send to user space.
	 */
	if (!buf->snapshot && lost)
		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);

	cur = buf->cur;
	offset = buf->offset;
	barrier = coresight_barrier_pkt;

	/* for every byte to read */
	for (i = 0; i < to_read; i += 4) {
		buf_ptr = buf->data_pages[cur] + offset;
		*buf_ptr = readl_relaxed(drvdata->base + TMC_RRD);

		if (lost && i < CORESIGHT_BARRIER_PKT_SIZE) {
			*buf_ptr = *barrier;
			barrier++;
		}

		offset += 4;
		if (offset >= PAGE_SIZE) {
			offset = 0;
			cur++;
			/* wrap around at the end of the buffer */
			cur &= buf->nr_pages - 1;
		}
	}

	/*
	 * In snapshot mode we simply increment the head by the number of byte
	 * that were written.  User space will figure out how many bytes to get
	 * from the AUX buffer based on the position of the head.
	 */
	if (buf->snapshot)
		handle->head += to_read;

	/*
	 * CS_LOCK() contains mb() so it can ensure visibility of the AUX trace
	 * data before the aux_head is updated via perf_aux_output_end(), which
	 * is expected by the perf ring buffer.
	 */
	CS_LOCK(drvdata->base);
out:
	spin_unlock_irqrestore(&drvdata->spinlock, flags);

	return to_read;
}