From: Miquel Raynal miquel.raynal@bootlin.com
[ Upstream commit e4fb03fe10c5e7a5d9aef7cefe815253274fb9ee ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 0efe4df24622..b3abc29aa927 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; @@ -331,6 +333,22 @@ 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 b3c3f7e5851a..1bdc8d6432fe 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -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);