Hello again,
On Tue, Nov 23, 2021 at 08:51:22AM +0100, Uwe Kleine-König wrote:
> On Tue, Nov 23, 2021 at 03:04:37PM +0800, Sherry Sun wrote:
> > From: Fugang Duan <fugang.duan@xxxxxxx>
> >
> > Disable UCR4_OREN bit in .stop_rx() to avoid endless
> > interrupt happen while tty port is closing.
> >
> > Signed-off-by: Fugang Duan <fugang.duan@xxxxxxx>
> > Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
> > ---
> > drivers/tty/serial/imx.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> > index fb75e3e0d828..9ecaf051249d 100644
> > --- a/drivers/tty/serial/imx.c
> > +++ b/drivers/tty/serial/imx.c
> > @@ -486,18 +486,21 @@ static void imx_uart_stop_tx(struct uart_port *port)
> > static void imx_uart_stop_rx(struct uart_port *port)
> > {
> > struct imx_port *sport = (struct imx_port *)port;
> > - u32 ucr1, ucr2;
> > + u32 ucr1, ucr2, ucr4;
> >
> > ucr1 = imx_uart_readl(sport, UCR1);
> > ucr2 = imx_uart_readl(sport, UCR2);
> > + ucr4 = imx_uart_readl(sport, UCR4);
> >
> > if (sport->dma_is_enabled) {
> > ucr1 &= ~(UCR1_RXDMAEN | UCR1_ATDMAEN);
> > } else {
> > ucr1 &= ~UCR1_RRDYEN;
> > ucr2 &= ~UCR2_ATEN;
> > + ucr4 &= ~UCR4_OREN;
> > }
> > imx_uart_writel(sport, ucr1, UCR1);
> > + imx_uart_writel(sport, ucr4, UCR4);
>
> I don't understand this yet, but I guess this is just a matter of
> improving the commit log. How does the endless irq happen?
>
> ... some time later after thinking and reading the driver source ...
>
> Hmm, when the OR event is triggered the handler does
>
> imx_uart_writel(sport, USR2_ORE, USR2);
>
> and so clears the event. I would expect that this should be good enough
> to prevent an irq storm even if the receiver is disabled. Doesn't acking
> work with the receiver disabled?
One thing I forgot to mention:
If imx_uart_stop_rx() now clears UCR4_OREN, clearing in
imx_uart_shutdown() should probably be dropped.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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