Re: [PATCH v1] tty: serial: imx: enable IDDMAEN for the last tail data
From: Uwe Kleine-König <hidden>
Date: 2018-09-20 07:55:27
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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
quoted hunk ↗ jump to hunk
Signed-off-by: Robin Gong <redacted> --- 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/ |