+ * return number of bytes in unsent transmit DMA buffers
+ * and the serial controller tx FIFO
+ */
+static unsigned int tbuf_bytes(struct slgt_info *info)
+{
+ unsigned int total_count = 0;
+ unsigned int i = info->tbuf_current;
+ unsigned int reg_value;
+ unsigned int count;
+ unsigned int active_buf_count = 0;
+
+ /*
+ * Add descriptor counts for all tx DMA buffers.
+ * If count is zero (cleared by DMA controller after read),
+ * the buffer is complete or is actively being read from.
+ *
+ * Record buf_count of last buffer with zero count starting
+ * from current ring position. buf_count is mirror
+ * copy of count and is not cleared by serial controller.
+ * If DMA controller is active, that buffer is actively
+ * being read so add to total.
+ */
+ do {
+ count = desc_count(info->tbufs[i]);
+ if (count)
+ total_count += count;
+ else if (!total_count)
+ active_buf_count = info->tbufs[i].buf_count;
+ if (++i == info->tbuf_count)
+ i = 0;
+ } while (i != info->tbuf_current);
+
+ /* read tx DMA status register */
+ reg_value = rd_reg32(info, TDCSR);
+
+ /* if tx DMA active, last zero count buffer is in use */
+ if (reg_value & BIT0)
+ total_count += active_buf_count;
+
+ /* add tx FIFO count = reg_value[15..8] */
+ total_count += (reg_value >> 8) & 0xff;
+
+ /* if transmitter active add one byte for shift register */
+ if (info->tx_active)
+ total_count++;
+
+ return total_count;
+}
+
+/*