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@xxxxxxxxx>
---
v3:
- New.
---
drivers/tty/serial/sh-sci.c | 50 ++++++++++++++++++---------------------------
1 file changed, 20 insertions(+), 30 deletions(-)
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index cb35c88645bb5784..5a528b8985052017 100644
--- 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);
}
--
1.9.1
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