Re: [PATCH v4 4/4] serial: 8250_dw: fix PSLVERR on RX_TIMEOUT

[Jiri Slaby]

On 25. 04. 25, 8:41, Jiri Slaby wrote:
> On 25. 04. 25, 8:24, Yunhui Cui wrote:
> > In the case of RX_TIMEOUT, to avoid PSLVERR, disable the FIFO
> > before reading UART_RX when UART_LSR_DR is not set.
> >
> > Fixes: 424d79183af0 ("serial: 8250_dw: Avoid "too much work" from 
> > bogus rx timeout interrupt")
> > Signed-off-by: Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx>
> > ---
> >   drivers/tty/serial/8250/8250_dw.c | 13 ++++++++++++-
> >   1 file changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/ 
> > serial/8250/8250_dw.c
> > index 07f9be074b4b..1e364280a108 100644
> > --- a/drivers/tty/serial/8250/8250_dw.c
> > +++ b/drivers/tty/serial/8250/8250_dw.c
> > @@ -273,6 +273,7 @@ static int dw8250_handle_irq(struct uart_port *p)
> >       unsigned int quirks = d->pdata->quirks;
> >       unsigned int status;
> >       unsigned long flags;
> > +    unsigned char old_fcr;
>
> No more unsigned char, please. Use u8.
>
> > @@ -288,9 +289,19 @@ static int dw8250_handle_irq(struct uart_port *p)
> >           uart_port_lock_irqsave(p, &flags);
> >           status = serial_lsr_in(up);
> > -        if (!(status & (UART_LSR_DR | UART_LSR_BI)))
> > +        if (!(status & (UART_LSR_DR | UART_LSR_BI))) {
> > +            /* To avoid PSLVERR, disable the FIFO first. */
> > +            if (up->fcr & UART_FCR_ENABLE_FIFO) {
> > +                old_fcr = serial_in(up, UART_FCR);

Wait, read(FCR) actually means read(IIR). FCR is write only. Or is DW 
special in this?

> > +                serial_out(up, UART_FCR, old_fcr & ~1);
>
> s/1/UART_FCR_ENABLE_FIFO/
>
> > +            }
> > +
> >               (void) p->serial_in(p, UART_RX);
> > +            if (up->fcr & UART_FCR_ENABLE_FIFO)
> > +                serial_out(up, UART_FCR, old_fcr);
> > +        }
> > +
> >           uart_port_unlock_irqrestore(p, flags);
> >       }

--
js
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