> -----Original Message----- > From: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> > Sent: 2018年9月20日 15:55 > To: Robin Gong <yibin.gong@xxxxxxx> > Cc: jslaby@xxxxxxxx; Andy Duan <fugang.duan@xxxxxxx>; > linux-serial@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; dl-linux-imx > <linux-imx@xxxxxxx>; kernel@xxxxxxxxxxxxxx > Subject: Re: [PATCH v1] tty: serial: imx: enable IDDMAEN for the last tail data > > 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. It's a real fix, you will see 'timeout We read 0 byte' with the attached stress test running on i.mx7d or i.mx6 if no this patch applied. ' while [ 1 ]; do /unit_tests/UART/mxc_uart_stress_test.out /dev/ttymxc5 2000000 D L 100 100 L; done &' Please make sure dma enabled on ttymxcX for your test, and sdma firmware setup in your rootfs /lib/firmware/imx/sdma/sdma-imx6q.bin or /lib/firmware/imx/sdma/sdma-imx7d.bin. You can get sdma firmware from below: https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/imx/sdma > > 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 | > https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww. > pengutronix.de%2F&data=02%7C01%7Cyibin.gong%40nxp.com%7Cebbc2 > 26ea12d4f6dd93b08d61ece6add%7C686ea1d3bc2b4c6fa92cd99c5c301635%7 > C0%7C0%7C636730269265048370&sdata=7NstF74mOGOFajEwFjBw7FAh > h3JdvGAIC9nliwrsf0Y%3D&reserved=0 |
Attachment:
mxc_uart_stress_test.out
Description: mxc_uart_stress_test.out
