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Commit 79904420 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Greg Kroah-Hartman
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serial: sh-sci: Switch to dma_map_single() for DMA transmission 



Simplify the DMA transmit code by using dma_map_single() instead of
constantly modifying the single-entry scatterlist to match what's
currently being transmitted.

Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 092248aa

drivers/tty/serial/sh-sci.c

+20 −30
Original line number Diff line number Diff line
@@ -109,8 +109,8 @@ struct sci_port { 
	dma_cookie_t			cookie_tx;

	dma_cookie_t			cookie_rx[2];

	dma_cookie_t			active_rx;

	struct scatterlist		sg_tx;

	unsigned int			sg_len_tx;

	dma_addr_t			tx_dma_addr;

	unsigned int			tx_dma_len;

	struct scatterlist		sg_rx[2];

	size_t				buf_len_rx;

	struct sh_dmae_slave		param_tx;
@@ -1280,10 +1280,10 @@ static void sci_dma_tx_complete(void *arg) 


	spin_lock_irqsave(&port->lock, flags);



	xmit->tail += sg_dma_len(&s->sg_tx);

	xmit->tail += s->tx_dma_len;

	xmit->tail &= UART_XMIT_SIZE - 1;



	port->icount.tx += sg_dma_len(&s->sg_tx);

	port->icount.tx += s->tx_dma_len;



	async_tx_ack(s->desc_tx);

	s->desc_tx = NULL;
@@ -1494,7 +1494,7 @@ static void work_fn_tx(struct work_struct *work) 
	struct dma_chan *chan = s->chan_tx;

	struct uart_port *port = &s->port;

	struct circ_buf *xmit = &port->state->xmit;

	struct scatterlist *sg = &s->sg_tx;

	dma_addr_t buf;



	/*

	 * DMA is idle now.
@@ -1504,18 +1504,14 @@ static void work_fn_tx(struct work_struct *work) 
	 * consistent xmit buffer state.

	 */

	spin_lock_irq(&port->lock);

	sg->offset = xmit->tail & (UART_XMIT_SIZE - 1);

	sg_dma_address(sg) = (sg_dma_address(sg) & ~(UART_XMIT_SIZE - 1)) +

		sg->offset;

	sg_dma_len(sg) = min_t(unsigned int,

	buf = s->tx_dma_addr + (xmit->tail & (UART_XMIT_SIZE - 1));

	s->tx_dma_len = min_t(unsigned int,

		CIRC_CNT(xmit->head, xmit->tail, UART_XMIT_SIZE),

		CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE));

	spin_unlock_irq(&port->lock);



	BUG_ON(!sg_dma_len(sg));



	desc = dmaengine_prep_slave_sg(chan,

			sg, s->sg_len_tx, DMA_MEM_TO_DEV,

	desc = dmaengine_prep_slave_single(chan, buf, s->tx_dma_len,

					   DMA_MEM_TO_DEV,

					   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

	if (!desc) {

		dev_warn(port->dev, "Failed preparing Tx DMA descriptor\n");
@@ -1524,7 +1520,8 @@ static void work_fn_tx(struct work_struct *work) 
		return;

	}



	dma_sync_sg_for_device(chan->device->dev, sg, 1, DMA_TO_DEVICE);

	dma_sync_single_for_device(chan->device->dev, buf, s->tx_dma_len,

				   DMA_TO_DEVICE);



	spin_lock_irq(&port->lock);

	s->desc_tx = desc;
@@ -1680,7 +1677,6 @@ static void sci_request_dma(struct uart_port *port) 
	struct sh_dmae_slave *param;

	struct dma_chan *chan;

	dma_cap_mask_t mask;

	int nent;



	dev_dbg(port->dev, "%s: port %d\n", __func__, port->line);
@@ -1700,27 +1696,21 @@ static void sci_request_dma(struct uart_port *port) 
	dev_dbg(port->dev, "%s: TX: got channel %p\n", __func__, chan);

	if (chan) {

		s->chan_tx = chan;

		sg_init_table(&s->sg_tx, 1);

		/* UART circular tx buffer is an aligned page. */

		BUG_ON((uintptr_t)port->state->xmit.buf & ~PAGE_MASK);

		sg_set_page(&s->sg_tx, virt_to_page(port->state->xmit.buf),

		s->tx_dma_addr = dma_map_single(chan->device->dev,

						port->state->xmit.buf,

						UART_XMIT_SIZE,

			    (uintptr_t)port->state->xmit.buf & ~PAGE_MASK);

		nent = dma_map_sg(chan->device->dev, &s->sg_tx, 1,

						DMA_TO_DEVICE);

		if (!nent) {

		if (dma_mapping_error(chan->device->dev, s->tx_dma_addr)) {

			dev_warn(port->dev, "Failed mapping Tx DMA descriptor\n");

			dma_release_channel(chan);

			s->chan_tx = NULL;

		} else {

			dev_dbg(port->dev, "%s: mapped %d@%p to %pad\n",

				__func__,

				sg_dma_len(&s->sg_tx), port->state->xmit.buf,

				&sg_dma_address(&s->sg_tx));

			dev_dbg(port->dev, "%s: mapped %lu@%p to %pad\n",

				__func__, UART_XMIT_SIZE,

				port->state->xmit.buf, &s->tx_dma_addr);

		}



		s->sg_len_tx = nent;



		INIT_WORK(&s->work_tx, work_fn_tx);

	}