soundwire: use bra if msg size > threshold

It is more efficient to read/write with bra if the message size is
larger than a predefined threshold.

Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>

Author: bardliao

drivers/soundwire/bus.c

@@ -447,6 +447,33 @@ static int sdw_ntransfer_no_pm(struct sdw_slave *slave, u32 addr, u8 flags,
 	return 0;
 }
 
+static int sdw_ntransfer_no_pm_bpt(struct sdw_slave *slave, u32 addr, u8 flags,
+				   size_t count, u8 *val)
+{
+	struct sdw_bpt_section sec;
+	struct sdw_bpt_msg msg;
+	int retry = 5;
+	int ret;
+
+	sec.addr = addr;
+	sec.len = count;
+	sec.buf = val;
+
+	msg.sections = 1;
+	msg.dev_num = slave->dev_num;
+	msg.flags = flags;
+	msg.sec = &sec;
+
+	do {
+		ret = sdw_bpt_send_sync(slave->bus, slave, &msg);
+		if (ret == -EAGAIN)
+			msleep(10);
+		retry--;
+	} while (ret == -EAGAIN && retry > 0);
+
+	return ret;
+}
+
 /**
  * sdw_nread_no_pm() - Read "n" contiguous SDW Slave registers with no PM
  * @slave: SDW Slave
@@ -459,6 +486,15 @@ static int sdw_ntransfer_no_pm(struct sdw_slave *slave, u32 addr, u8 flags,
  */
 int sdw_nread_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 {
+	int ret;
+
+	if (count < slave->bus->bra_r_threshold)
+		goto fallback;
+
+	ret = sdw_ntransfer_no_pm_bpt(slave, addr, SDW_MSG_FLAG_READ, count, val);
+	if (!ret)
+		return 0;
+fallback:
 	return sdw_ntransfer_no_pm(slave, addr, SDW_MSG_FLAG_READ, count, val);
 }
 EXPORT_SYMBOL(sdw_nread_no_pm);
@@ -475,6 +511,15 @@ EXPORT_SYMBOL(sdw_nread_no_pm);
  */
 int sdw_nwrite_no_pm(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val)
 {
+	int ret;
+
+	if (count < slave->bus->bra_w_threshold)
+		goto fallback;
+
+	ret = sdw_ntransfer_no_pm_bpt(slave, addr, SDW_MSG_FLAG_WRITE, count, (u8 *)val);
+	if (!ret)
+		return 0;
+fallback:
 	return sdw_ntransfer_no_pm(slave, addr, SDW_MSG_FLAG_WRITE, count, (u8 *)val);
 }
 EXPORT_SYMBOL(sdw_nwrite_no_pm);