Merge pull request #35 from htot/hsu_dma_optimize

Hsu dma optimize

drivers/tty/serial/8250/8250.h

@@ -51,6 +51,9 @@ struct uart_8250_dma {
 	unsigned char		tx_running;
 	unsigned char		tx_err;
 	unsigned char		rx_running;
+
+	unsigned int		dma_tx_nents;
+	struct scatterlist	tx_sgl[2];
 };
 
 struct old_serial_port {

drivers/tty/serial/8250/8250_dma.c

@@ -62,10 +62,13 @@ static void __dma_rx_complete(void *param)
 int serial8250_tx_dma(struct uart_8250_port *p)
 {
 	struct uart_8250_dma		*dma = p->dma;
+	struct scatterlist 		*sgl = dma->tx_sgl;
 	struct circ_buf			*xmit = &p->port.state->xmit;
 	struct dma_async_tx_descriptor	*desc;
 	struct uart_port		*up = &p->port;
 	int ret;
+	size_t				chunk1, chunk2;
+	int				head, tail;
 
 	if (dma->tx_running) {
 		if (up->x_char) {
@@ -83,7 +86,24 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 		return 0;
 	}
 
-	dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+	head = READ_ONCE(xmit->head);
+	tail = READ_ONCE(xmit->tail);
+	dma->dma_tx_nents = 1;
+	chunk1 = CIRC_CNT_TO_END(head, tail, UART_XMIT_SIZE);
+	chunk2 = CIRC_CNT(head, tail, UART_XMIT_SIZE) - chunk1;
+	if (chunk2 == 0) {
+		sg_init_one(sgl, xmit->buf + tail, chunk1);
+	} else {
+		dma->dma_tx_nents++;
+		sg_init_table(sgl, dma->dma_tx_nents);
+		sg_set_buf(&sgl[0], xmit->buf + tail, chunk1);
+		sg_set_buf(&sgl[1], xmit->buf, chunk2);
+		sg_dma_address(&sgl[1]) = dma->tx_addr;
+		sg_dma_len(&sgl[1]) = chunk2;
+	}
+	sg_dma_address(&sgl[0]) = dma->tx_addr + tail;
+	sg_dma_len(&sgl[0]) = chunk1;
+	dma->tx_size = chunk1 + chunk2;
 
 	serial8250_do_prepare_tx_dma(p);
 

drivers/tty/serial/8250/8250_mid.c

@@ -93,6 +93,8 @@ static int tng_handle_irq(struct uart_port *p)
 	err = hsu_dma_get_status(chip, mid->dma_index * 2 + 1, &status);
 	if (err > 0) {
 		serial8250_rx_dma_flush(up);
+		/* Immediately after flushing arm DMA again */
+		if (up->dma) up->dma->rx_dma(up);
 		ret |= 1;
 	} else if (err == 0)
 		ret |= hsu_dma_do_irq(chip, mid->dma_index * 2 + 1, status);
@@ -242,6 +244,29 @@ static void mid8250_set_termios(struct uart_port *p,
 	serial8250_do_set_termios(p, termios, old);
 }
 
+static int mid8250_startup(struct uart_port *port)
+{
+	struct uart_8250_port *up = up_to_u8250p(port);
+	int ret;
+
+	ret = serial8250_do_startup(port);
+
+	/* Arm Rx DMA at ->startup() time */
+
+	if (up->dma) up->dma->rx_dma(up);
+
+	return ret;
+}
+
+static void mid8250_shutdown(struct uart_port *port)
+{
+	struct uart_8250_port *up = up_to_u8250p(port);
+
+	if (up->dma) serial8250_rx_dma_flush(up);
+
+	serial8250_do_shutdown(port);
+}
+
 static bool mid8250_dma_filter(struct dma_chan *chan, void *param)
 {
 	struct hsu_dma_slave *s = param;
@@ -316,6 +341,8 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	uart.port.uartclk = mid->board->base_baud * 16;
 	uart.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE;
 	uart.port.set_termios = mid8250_set_termios;
+	uart.port.startup = mid8250_startup;
+	uart.port.shutdown = mid8250_shutdown;
 
 	uart.port.mapbase = pci_resource_start(pdev, bar);
 	uart.port.membase = pcim_iomap(pdev, bar, 0);

drivers/tty/serial/8250/8250_port.c

@@ -2418,6 +2418,13 @@ int serial8250_do_startup(struct uart_port *port)
 		if (msg) {
 			dev_warn_ratelimited(port->dev, "%s\n", msg);
 			up->dma = NULL;
+		} else {
+			/*
+			 * change tty_io write() to not split
+			 * large writes into 2K chunks
+			 */
+			set_bit(TTY_NO_WRITE_SPLIT,
+				&port->state->port.tty->flags);
 		}
 	}