[PATCH v2 02/11] coresight: trbe: Refactor next buffer computation

[Leo Yan <leo.yan@arm.com>]

compute_trbe_buffer_limit() only returned the next TRBE limit pointer,
leaving __arm_trbe_enable() to derive the remaining buffer state and
detect the -ENOSPC case.

Replace it with trbe_compute_next(), which computes the next TRBE buffer
state as one operation. Let the snapshot and normal paths set
buf->trbe_limit directly and return 0 or an errno, then update
trbe_write and trbe_hw_base after a successful limit calculation. The
normal path now reports -ENOSPC directly when no writable area is
available.

This refactoring is for future extensions, such as calculating
additional values (e.g., the trigger count). No functional changes are
intended.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 drivers/hwtracing/coresight/coresight-trbe.c | 44 +++++++++++++++++-----------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index ada4794c51f3eb9142cd62f4209affe308142d1b..09ed9bcf4a70479169094697dcc3d445629cfaae 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -349,7 +349,7 @@ static void trbe_pad_buf(struct perf_output_handle *handle, int len)
 		perf_aux_output_skip(handle, len);
 }
 
-static unsigned long trbe_snapshot_offset(struct perf_output_handle *handle)
+static int trbe_snapshot_offset(struct perf_output_handle *handle)
 {
 	struct trbe_buf *buf = etm_perf_sink_config(handle);
 
@@ -358,7 +358,8 @@ static unsigned long trbe_snapshot_offset(struct perf_output_handle *handle)
 	 * the decoder to reset in case of an overflow or corruption.
 	 * So we can use the entire buffer for the snapshot mode.
 	 */
-	return buf->nr_pages * PAGE_SIZE;
+	buf->trbe_limit = buf->trbe_base + buf->nr_pages * PAGE_SIZE;
+	return 0;
 }
 
 static u64 trbe_min_trace_buf_size(struct perf_output_handle *handle)
@@ -527,7 +528,7 @@ static unsigned long __trbe_normal_offset(struct perf_output_handle *handle)
 	return 0;
 }
 
-static unsigned long trbe_normal_offset(struct perf_output_handle *handle)
+static int trbe_normal_offset(struct perf_output_handle *handle)
 {
 	struct trbe_buf *buf = etm_perf_sink_config(handle);
 	u64 limit = __trbe_normal_offset(handle);
@@ -546,19 +547,34 @@ static unsigned long trbe_normal_offset(struct perf_output_handle *handle)
 		limit = __trbe_normal_offset(handle);
 		head = PERF_IDX2OFF(handle->head, buf);
 	}
-	return limit;
+
+	if (!limit)
+		return -ENOSPC;
+
+	buf->trbe_limit = buf->trbe_base + limit;
+	return 0;
 }
 
-static unsigned long compute_trbe_buffer_limit(struct perf_output_handle *handle)
+static int trbe_compute_next(struct perf_output_handle *handle)
 {
 	struct trbe_buf *buf = etm_perf_sink_config(handle);
-	unsigned long offset;
+	int ret;
+
+	perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW);
 
 	if (buf->snapshot)
-		offset = trbe_snapshot_offset(handle);
+		ret = trbe_snapshot_offset(handle);
 	else
-		offset = trbe_normal_offset(handle);
-	return buf->trbe_base + offset;
+		ret = trbe_normal_offset(handle);
+
+	if (ret)
+		return ret;
+
+	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
+
+	/* Set the base of the TRBE to the buffer base */
+	buf->trbe_hw_base = buf->trbe_base;
+	return 0;
 }
 
 static void clr_trbe_status(void)
@@ -1022,15 +1038,9 @@ static int __arm_trbe_enable(struct trbe_buf *buf,
 {
 	int ret = 0;
 
-	perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW);
-	buf->trbe_limit = compute_trbe_buffer_limit(handle);
-	buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
-	if (buf->trbe_limit == buf->trbe_base) {
-		ret = -ENOSPC;
+	ret = trbe_compute_next(handle);
+	if (ret)
 		goto err;
-	}
-	/* Set the base of the TRBE to the buffer base */
-	buf->trbe_hw_base = buf->trbe_base;
 
 	ret = trbe_apply_work_around_before_enable(buf);
 	if (ret)

-- 
2.34.1