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serial: 8250: dma: Allow driver operations before starting DMA transfers

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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@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20220422180615.9098-6-miquel.raynal@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Miquel Raynal 2022-04-22 20:06:11 +02:00 committed by Greg Kroah-Hartman
parent 593dea000b
commit e4fb03fe10
2 changed files with 22 additions and 0 deletions
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18
drivers/tty/serial/8250/8250.h
View File

@ -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;
@ -302,6 +304,22 @@ 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)
{

4
drivers/tty/serial/8250/8250_dma.c
View File

@ -86,6 +86,8 @@ 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,
@ -123,6 +125,8 @@ 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);