WIP: serial: 8250_dma: use sgl on transmit

Signed-off-by: Ferry Toth <ftoth@exalondelft.nl>
andy-shev · May 14, 2021 · 174a779 · 174a779
1 parent 200034f
commit 174a779
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Showing 2 changed files with 28 additions and 9 deletions.
diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
@@ -48,6 +48,9 @@ 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 {

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
@@ -15,12 +15,13 @@ static void __dma_tx_complete(void *param)
 {
  struct uart_8250_port *p = param;
  struct uart_8250_dma *dma = p->dma;
+ struct scatterlist *sgl = dma->tx_sgl;
  struct circ_buf *xmit = &p->port.state->xmit;
  unsigned long flags;
  int ret;
 
- dma_sync_single_for_cpu(dma->txchan->device->dev, dma->tx_addr,
- UART_XMIT_SIZE, DMA_TO_DEVICE);
+ dma_sync_sg_for_cpu(dma->txchan->device->dev, sgl,
+ dma->dma_tx_nents, DMA_TO_DEVICE);
 
  spin_lock_irqsave(&p->port.lock, flags);
 
@@ -60,9 +61,12 @@ static void __dma_rx_complete(struct uart_8250_port *p, struct uart_8250_dma *dm
 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;
  int ret;
+ size_t chunk1, chunk2;
+ int head, tail;
 
  if (dma->tx_running)
  return 0;
@@ -73,12 +77,24 @@ 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 = xmit->head;
+ tail = 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, xmit->buf + tail, chunk1);
+ sg_set_buf(sgl + 1, xmit->buf, chunk2);
+ }
+ dma->tx_size = chunk1 + chunk2;
 
- 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);
+ desc = dmaengine_prep_slave_sg(dma->txchan, sgl, dma->dma_tx_nents,
+ DMA_MEM_TO_DEV,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
  if (!desc) {
  ret = -EBUSY;
  goto err;
@@ -90,8 +106,8 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 
  dma->tx_cookie = dmaengine_submit(desc);
 
- dma_sync_single_for_device(dma->txchan->device->dev, dma->tx_addr,
-  UART_XMIT_SIZE, DMA_TO_DEVICE);
+ dma_sync_sg_for_device(dma->txchan->device->dev, sgl,
+ dma->dma_tx_nents, DMA_TO_DEVICE);
 
  dma_async_issue_pending(dma->txchan);
  if (dma->tx_err) {