One situation where this could be used is when configuring the UART
controller to be the DMA flow controller. This is a typical case where
the driver might need to program a few more registers before starting a
DMA transfer. Provide the necessary infrastructure to support this
case.
Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
---
drivers/tty/serial/8250/8250.h | 18 ++++++++++++++++++
drivers/tty/serial/8250/8250_dma.c | 4 ++++
2 files changed, 22 insertions(+)
diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
index db784ace25d8..d19f24e4d13e 100644
--- a/drivers/tty/serial/8250/8250.h
+++ b/drivers/tty/serial/8250/8250.h
@@ -17,6 +17,8 @@
struct uart_8250_dma {
int (*tx_dma)(struct uart_8250_port *p);
int (*rx_dma)(struct uart_8250_port *p);
+ void (*prepare_tx_dma)(struct uart_8250_port *p);
+ void (*prepare_rx_dma)(struct uart_8250_port *p);
/* Filter function */
dma_filter_fn fn;
@@ -301,6 +303,22 @@ extern int serial8250_rx_dma(struct uart_8250_port *);
extern void serial8250_rx_dma_flush(struct uart_8250_port *);
extern int serial8250_request_dma(struct uart_8250_port *);
extern void serial8250_release_dma(struct uart_8250_port *);
+
+static inline void serial8250_do_prepare_tx_dma(struct uart_8250_port *p)
+{
+ struct uart_8250_dma *dma = p->dma;
+
+ if (dma->prepare_tx_dma)
+ dma->prepare_tx_dma(p);
+}
+
+static inline void serial8250_do_prepare_rx_dma(struct uart_8250_port *p)
+{
+ struct uart_8250_dma *dma = p->dma;
+
+ if (dma->prepare_rx_dma)
+ dma->prepare_rx_dma(p);
+}
#else
static inline int serial8250_tx_dma(struct uart_8250_port *p)
{
diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 890fa7ddaa7f..558d3a2ac65b 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -77,6 +77,8 @@ int serial8250_tx_dma(struct uart_8250_port *p)
dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
+ 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,
@@ -114,6 +116,8 @@ int serial8250_rx_dma(struct uart_8250_port *p)
if (dma->rx_running)
return 0;
+ serial8250_do_prepare_rx_dma(p);
+
desc = dmaengine_prep_slave_single(dma->rxchan, dma->rx_addr,
dma->rx_size, DMA_DEV_TO_MEM,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
--
2.27.0
