On Wed, Mar 30, 2022 at 03:20:34PM +0200, Miquel Raynal wrote:
> 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.
OK!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> 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
>
--
With Best Regards,
Andy Shevchenko
