--- zzzz-none-000/linux-3.10.107/drivers/tty/serial/8250/8250_dma.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/drivers/tty/serial/8250/8250_dma.c	2021-02-04 17:41:59.000000000 +0000
@@ -21,6 +21,7 @@
 	struct uart_8250_dma	*dma = p->dma;
 	struct circ_buf		*xmit = &p->port.state->xmit;
 	unsigned long	flags;
+	int		ret;
 
 	dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
 				UART_XMIT_SIZE, DMA_TO_DEVICE);
@@ -36,8 +37,11 @@
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 		uart_write_wakeup(&p->port);
 
-	if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port))
-		serial8250_tx_dma(p);
+	ret = serial8250_tx_dma(p);
+	if (ret) {
+		p->ier |= UART_IER_THRI;
+		serial_port_out(&p->port, UART_IER, p->ier);
+	}
 
 	spin_unlock_irqrestore(&p->port.lock, flags);
 }
@@ -50,11 +54,8 @@
 	struct dma_tx_state	state;
 	int			count;
 
-	dma_sync_single_for_cpu(dma->rxchan->device->dev, dma->rx_addr,
-				dma->rx_size, DMA_FROM_DEVICE);
-
+	dma->rx_running = 0;
 	dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
-	dmaengine_terminate_all(dma->rxchan);
 
 	count = dma->rx_size - state.residue;
 
@@ -69,6 +70,7 @@
 	struct uart_8250_dma		*dma = p->dma;
 	struct circ_buf			*xmit = &p->port.state->xmit;
 	struct dma_async_tx_descriptor	*desc;
+	int ret;
 
 	if (uart_tx_stopped(&p->port) || dma->tx_running ||
 	    uart_circ_empty(xmit))
@@ -80,11 +82,12 @@
 					   dma->tx_addr + xmit->tail,
 					   dma->tx_size, DMA_MEM_TO_DEV,
 					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
-	if (!desc)
-		return -EBUSY;
+	if (!desc) {
+		ret = -EBUSY;
+		goto err;
+	}
 
 	dma->tx_running = 1;
-
 	desc->callback = __dma_tx_complete;
 	desc->callback_param = p;
 
@@ -94,19 +97,23 @@
 				   UART_XMIT_SIZE, DMA_TO_DEVICE);
 
 	dma_async_issue_pending(dma->txchan);
-
+	if (dma->tx_err) {
+		dma->tx_err = 0;
+		if (p->ier & UART_IER_THRI) {
+			p->ier &= ~UART_IER_THRI;
+			serial_out(p, UART_IER, p->ier);
+		}
+	}
 	return 0;
+err:
+	dma->tx_err = 1;
+	return ret;
 }
-EXPORT_SYMBOL_GPL(serial8250_tx_dma);
 
 int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
 {
 	struct uart_8250_dma		*dma = p->dma;
 	struct dma_async_tx_descriptor	*desc;
-	struct dma_tx_state		state;
-	int				dma_status;
-
-	dma_status = dmaengine_tx_status(dma->rxchan, dma->rx_cookie, &state);
 
 	switch (iir & 0x3f) {
 	case UART_IIR_RLSI:
@@ -117,16 +124,17 @@
 		 * If RCVR FIFO trigger level was not reached, complete the
 		 * transfer and let 8250_core copy the remaining data.
 		 */
-		if (dma_status == DMA_IN_PROGRESS) {
+		if (dma->rx_running) {
 			dmaengine_pause(dma->rxchan);
 			__dma_rx_complete(p);
+			dmaengine_terminate_all(dma->rxchan);
 		}
 		return -ETIMEDOUT;
 	default:
 		break;
 	}
 
-	if (dma_status)
+	if (dma->rx_running)
 		return 0;
 
 	desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
@@ -135,19 +143,16 @@
 	if (!desc)
 		return -EBUSY;
 
+	dma->rx_running = 1;
 	desc->callback = __dma_rx_complete;
 	desc->callback_param = p;
 
 	dma->rx_cookie = dmaengine_submit(desc);
 
-	dma_sync_single_for_device(dma->rxchan->device->dev, dma->rx_addr,
-				   dma->rx_size, DMA_FROM_DEVICE);
-
 	dma_async_issue_pending(dma->rxchan);
 
 	return 0;
 }
-EXPORT_SYMBOL_GPL(serial8250_rx_dma);
 
 int serial8250_request_dma(struct uart_8250_port *p)
 {