> -----Original Message----- > From: Frank Li <frank.li@xxxxxxx> > Sent: Thursday, January 9, 2025 12:41 AM > To: Sherry Sun <sherry.sun@xxxxxxx> > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; jirislaby@xxxxxxxxxx; linux- > serial@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] tty: serial: fsl_lpuart: flush RX and TX FIFO when lpuart > shutdown > > On Wed, Jan 08, 2025 at 03:03:05AM +0000, Sherry Sun wrote: > > > > > > > -----Original Message----- > > > From: Frank Li <frank.li@xxxxxxx> > > > Sent: Tuesday, January 7, 2025 11:46 PM > > > To: Sherry Sun <sherry.sun@xxxxxxx> > > > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; jirislaby@xxxxxxxxxx; linux- > > > serial@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > > imx@xxxxxxxxxxxxxxx > > > Subject: Re: [PATCH] tty: serial: fsl_lpuart: flush RX and TX FIFO > > > when lpuart shutdown > > > > > > On Tue, Jan 07, 2025 at 03:48:34PM +0800, Sherry Sun wrote: > > > > Need to flush UART RX and TX FIFO when lpuart is shutting down to > > > > make sure restore a clean data transfer environment. > > > > > > why not flush it at open()? > > > > Hi Frank, > > > > Some background: We observed an issue during imx952 zebu simulation, > imx952 edma IP has a bug that if an edma error occurs, it will directly return > an error without marking the current request completed, so the current uart > transfer will pending, the data will stuck in the FIFO even if we close the uart > port and reopen it, which will impact the next data transfer. > > Actually when we configure and enable the FIFO during uart startup, we > > also flush the RX/TX FIFO, but it is done after the rx/tx dma are > > started, > > Please wrap at 75 char to read easily. Hi Frank, sorry for that, will pay attention next time. :) > > It looks like make sense to move flash before start dma. Yes, as we discussed internally, this is an improvement needs to be done. Thanks for the suggestions. > > > so the dma request is still triggered by mistake. > > And I think it is reasonable to flush the RX/TX FIFO when closing the uart > port, so add this behavior in shutdown() to avoid changing the workflow of > startup(). > > the target is make driver logic reasonable, not avoid changing ... > if external devices continue send data, even you flash fifo in closing, it may > still have data in FIFO if uart have not disabled yet. > Since we flush the FIFO after disabling the receiver and transmitter, so this won't happen. Best Regards Sherry > > > > > > > > > > > Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx> > > > > --- > > > > drivers/tty/serial/fsl_lpuart.c | 5 +++++ > > > > 1 file changed, 5 insertions(+) > > > > > > > > diff --git a/drivers/tty/serial/fsl_lpuart.c > > > > b/drivers/tty/serial/fsl_lpuart.c index 7cb1e36fdaab..c91b9d9818cd > > > > 100644 > > > > --- a/drivers/tty/serial/fsl_lpuart.c > > > > +++ b/drivers/tty/serial/fsl_lpuart.c > > > > @@ -1965,6 +1965,11 @@ static void lpuart32_shutdown(struct > > > > uart_port > > > *port) > > > > UARTCTRL_TIE | UARTCTRL_TCIE | UARTCTRL_RIE | > > > UARTCTRL_SBK); > > > > lpuart32_write(port, temp, UARTCTRL); > > > > > > > > + /* flush Rx/Tx FIFO */ > > > > + temp = lpuart32_read(port, UARTFIFO); > > > > + temp |= UARTFIFO_TXFLUSH | UARTFIFO_RXFLUSH; > > > > + lpuart32_write(port, temp, UARTFIFO); > > > > + > > > > uart_port_unlock_irqrestore(port, flags); > > > > > > > > lpuart_dma_shutdown(sport); > > > > -- > > > > 2.34.1 > > > >
