| Message ID | 20250425062425.68761-4-cuiyunhui@bytedance.com |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
Hi js, On Fri, Apr 25, 2025 at 2:43 PM Jiri Slaby <jirislaby@kernel.org> wrote: > > 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@bytedance.com> > >> --- > >> 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? Indeed, the valid bits of the FCR are write-only. It seems that here we can only do serial_out(up, UART_FCR, up->fcr); What do you think? > > >> + 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 > suse labs > Thanks, Yunhui
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; /* * There are ways to get Designware-based UARTs into a state where @@ -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); + serial_out(up, UART_FCR, old_fcr & ~1); + } + (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); }
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@bytedance.com> --- drivers/tty/serial/8250/8250_dw.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)