> -----Original Message----- > From: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx> > Sent: 2022年11月9日 20:19 > To: Sherry Sun <sherry.sun@xxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Jiri Slaby > <jirislaby@xxxxxxxxxx>; linux-serial <linux-serial@xxxxxxxxxxxxxxx>; LKML > <linux-kernel@xxxxxxxxxxxxxxx>; dl-linux-imx <linux-imx@xxxxxxx> > Subject: Re: [PATCH 2/2] tty: serial: fsl_lpuart: improve lpuart32 registers > clearing when shutdown > > On Wed, 9 Nov 2022, Sherry Sun wrote: > > > Need to clear the UARTSTAT and UARTMODIR registers when shutdown the > > uart port, also clear the Rx/Tx DMA enable bits and loopback > > configuration bit. > > This lacks answer to "Why?" question. Think about somebody not as familiar > with the HW as you are looking back to this very commit message like 5 years > from now and wondering why this change was made. > > Preferrably make a separate change out of all these four changes if the > answers to why question are different. > > It would also help in deciding whether Fixes tag is necessary or not since you > didn't seem to include. Hi Ilpo, Ok, maybe I need to separate the four changes in lpuart32_shutdown() to better describe the "why". Thanks for the comments. Best Regards Sherry > > -- > i. > > > Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx> > > --- > > drivers/tty/serial/fsl_lpuart.c | 13 ++++++++++++- > > 1 file changed, 12 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/tty/serial/fsl_lpuart.c > > b/drivers/tty/serial/fsl_lpuart.c index f5a0a14fa366..43d9d6a6e94a > > 100644 > > --- a/drivers/tty/serial/fsl_lpuart.c > > +++ b/drivers/tty/serial/fsl_lpuart.c > > @@ -1771,11 +1771,22 @@ static void lpuart32_shutdown(struct > uart_port > > *port) > > > > spin_lock_irqsave(&port->lock, flags); > > > > + /* clear statue */ > > + temp = lpuart32_read(&sport->port, UARTSTAT); > > + lpuart32_write(&sport->port, temp, UARTSTAT); > > + > > + /* disable Rx/Tx DMA */ > > + temp = lpuart32_read(port, UARTBAUD); > > + temp &= ~(UARTBAUD_TDMAE | UARTBAUD_RDMAE); > > + lpuart32_write(port, temp, UARTBAUD); > > + > > /* disable Rx/Tx and interrupts */ > > temp = lpuart32_read(port, UARTCTRL); > > temp &= ~(UARTCTRL_TE | UARTCTRL_RE | UARTCTRL_ILIE | > > - UARTCTRL_TIE | UARTCTRL_TCIE | UARTCTRL_RIE); > > + UARTCTRL_TIE | UARTCTRL_TCIE | UARTCTRL_RIE | > > + UARTCTRL_LOOPS); > > lpuart32_write(port, temp, UARTCTRL); > > + lpuart32_write(port, 0, UARTMODIR); > > > > spin_unlock_irqrestore(&port->lock, flags); > > > >
