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: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index cb35c88645bb57845e11b9692b519424ac1b9b5d..5a528b8985052017688fd539219b103a04ed1585 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -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.
@@ -1504,19 +1504,15 @@ 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,
-                       DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+       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");
                /* switch to PIO */
@@ -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),
-                           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) {
+               s->tx_dma_addr = dma_map_single(chan->device->dev,
+                                               port->state->xmit.buf,
+                                               UART_XMIT_SIZE,
+                                               DMA_TO_DEVICE);
+               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);
        }