[PATCH v2 2/3] serial: mxs: enable the DMA only when the RTS/CTS is valid

[u.kleine-koenig@pengutronix.de (Uwe Kleine-König)]

On Tue, Jul 16, 2013 at 02:55:31PM +0800, Huang Shijie wrote:
> The original DMA support works only when RTS/CTS is enabled.
What is original here?

> But after several patches, DMA support has lost this limit.
This is still misleading.

> This patch adds an optional property for the UART DT node
> which indicates the UART has RTS and CTS lines.
> 
> This patch also adds a macro MXS_AUART_RTSCTS, and uses it to check
> RTS/CTS before we enable the DMA for the UART.

I still think this should go to stable. The options are:

	a) also take patch 1 into stable
	b) apply this patch without patch 1

I don't know if option a) is OK, b) is probably preferable. And as Greg
has much to do anyhow, better move this patch first. (Otherwise he will
probably only say: That patch doesn't apply, please help.)

> Signed-off-by: Huang Shijie <b32955@freescale.com>
> ---
>  .../bindings/tty/serial/fsl-mxs-auart.txt          |    4 ++++
>  drivers/tty/serial/mxs-auart.c                     |    5 ++++-
>  2 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> index 2c00ec6..59a40f1 100644
> --- a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> +++ b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> @@ -10,6 +10,10 @@ Required properties:
>    Refer to dma.txt and fsl-mxs-dma.txt for details.
>  - dma-names: "rx" for RX channel, "tx" for TX channel.
>  
> +Optional properties:
> +- fsl,uart-has-rtscts : Indicate the UART has RTS and CTS lines,
> +	it also means you enable the DMA support for this UART.
> +
>  Example:
>  auart0: serial at 8006a000 {
>  	compatible = "fsl,imx28-auart", "fsl,imx23-auart";
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> index 465ef0b..27532fd 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -134,6 +134,7 @@ enum mxs_auart_type {
>  struct mxs_auart_port {
>  	struct uart_port port;
>  
> +#define MXS_AUART_RTSCTS	1
>  #define MXS_AUART_DMA_ENABLED	0x2
>  #define MXS_AUART_DMA_TX_SYNC	2  /* bit 2 */
>  #define MXS_AUART_DMA_RX_READY	3  /* bit 3 */
> @@ -639,7 +640,7 @@ static void mxs_auart_settermios(struct uart_port *u,
>  		 * we can only implement the DMA support for auart
>  		 * in mx28.
>  		 */
> -		if (is_imx28_auart(s)) {
> +		if (is_imx28_auart(s) && (s->flags & MXS_AUART_RTSCTS)) {
I thought you wanted to add a comment here. Without knowing the details

	if (RTSCTS)
		enable_dma();

looks strange.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |