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charset="utf-8" From: Robin Gong Since sdma hardware configure postpone to transfer phase, have to disable dma request before dma transfer setup because there is a hardware limitation on sdma event enable(ENBLn) as below. Refer SDMA 2.6.28 Channel Enable RAM (SDMAARMx_CHNENBLn) section: "It is thus essential for the Arm platform to program them before any DMA request is triggered to the SDMA, otherwise an unpredictable combination of channels may be started." Signed-off-by: Robin Gong Signed-off-by: Sherry Sun --- drivers/tty/serial/imx.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index c488e5d372ff..251a50c8aa38 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -1442,9 +1442,9 @@ static void imx_uart_enable_dma(struct imx_port *spor= t) =20 imx_uart_setup_ufcr(sport, TXTL_DMA, RXTL_DMA); =20 - /* set UCR1 */ + /* set UCR1 except TXDMAEN which would be enabled in imx_uart_dma_tx */ ucr1 =3D imx_uart_readl(sport, UCR1); - ucr1 |=3D UCR1_RXDMAEN | UCR1_TXDMAEN | UCR1_ATDMAEN; + ucr1 |=3D UCR1_RXDMAEN | UCR1_ATDMAEN; imx_uart_writel(sport, ucr1, UCR1); =20 sport->dma_is_enabled =3D 1; @@ -1567,8 +1567,9 @@ static int imx_uart_startup(struct uart_port *port) imx_uart_enable_ms(&sport->port); =20 if (dma_is_inited) { - imx_uart_enable_dma(sport); + /* Note: enable dma request after transfer start! */ imx_uart_start_rx_dma(sport); + imx_uart_enable_dma(sport); } else { ucr1 =3D imx_uart_readl(sport, UCR1); ucr1 |=3D UCR1_RRDYEN; --=20 2.37.1