Hello,
On Thu, Sep 20, 2018 at 11:26:00PM +0800, Robin Gong wrote:
> enable IDDMAEN in UCR4 to let sdma script has the chance to detect
> the idle status and transfer the last tail data with the interrupt
> notifying uart driver.Otherwise, the last dma done interrupt of the
> tail data in rxfifo whose size is less than watermark may never be
> received by uart driver.
Is this a theoretic issue? Or does it fix a real problem?
If the former I'd say UCR1_ATDMAEN being set should prevent this stall.
Also I'd say the SDMA scripts I know don't properly handle the IDDMA
request.
Best regards
Uwe
> Signed-off-by: Robin Gong <yibin.gong@xxxxxxx>
> ---
> drivers/tty/serial/imx.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 239c0fa..bbb1693 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1278,7 +1278,7 @@ static int imx_uart_dma_init(struct imx_port *sport)
>
> static void imx_uart_enable_dma(struct imx_port *sport)
> {
> - u32 ucr1;
> + u32 ucr1, ucr4;
>
> imx_uart_setup_ufcr(sport, TXTL_DMA, RXTL_DMA);
>
> @@ -1287,18 +1287,26 @@ static void imx_uart_enable_dma(struct imx_port *sport)
> ucr1 |= UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN;
> imx_uart_writel(sport, ucr1, UCR1);
>
> + ucr4 = imx_uart_readl(sport, UCR4);
> + ucr4 |= UCR4_IDDMAEN;
> + imx_uart_writel(sport, ucr4, UCR4);
> +
> sport->dma_is_enabled = 1;
> }
>
> static void imx_uart_disable_dma(struct imx_port *sport)
> {
> - u32 ucr1;
> + u32 ucr1, ucr4;
>
> /* clear UCR1 */
> ucr1 = imx_uart_readl(sport, UCR1);
> ucr1 &= ~(UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN);
> imx_uart_writel(sport, ucr1, UCR1);
>
> + ucr4 = imx_uart_readl(sport, UCR4);
> + ucr4 &= ~UCR4_IDDMAEN;
> + imx_uart_writel(sport, ucr4, UCR4);
> +
> imx_uart_setup_ufcr(sport, TXTL_DEFAULT, RXTL_DEFAULT);
>
> sport->dma_is_enabled = 0;
> --
> 2.7.4
>
>
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
