[RFT 09/15] tty: 8250_dma: use dmaengine_prep_slave_sg()

From: Jiri Slaby (SUSE)
Date: Tue Mar 19 2024 - 05:56:17 EST


This is a preparatory for the serial-to-kfifo switch. kfifo understands
only scatter-gatter approach, so switch to that.

No functional change intended, it's just dmaengine_prep_slave_single()
inline expanded.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@xxxxxxxxxx>
---
drivers/tty/serial/8250/8250_dma.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 8b30ca8fdd3f..8b2c3f478b17 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -89,6 +89,7 @@ int serial8250_tx_dma(struct uart_8250_port *p)
struct circ_buf *xmit = &p->port.state->xmit;
struct dma_async_tx_descriptor *desc;
struct uart_port *up = &p->port;
+ struct scatterlist sg;
int ret;

if (dma->tx_running) {
@@ -111,10 +112,13 @@ int serial8250_tx_dma(struct uart_8250_port *p)

serial8250_do_prepare_tx_dma(p);

- desc = dmaengine_prep_slave_single(dma->txchan,
- dma->tx_addr + xmit->tail,
- dma->tx_size, DMA_MEM_TO_DEV,
- DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ sg_init_table(&sg, 1);
+ sg_dma_address(&sg) = dma->tx_addr + xmit->tail;
+ sg_dma_len(&sg) = dma->tx_size;
+
+ desc = dmaengine_prep_slave_sg(dma->txchan, &sg, 1,
+ DMA_MEM_TO_DEV,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
if (!desc) {
ret = -EBUSY;
goto err;
--
2.44.0