diff options
| -rw-r--r-- | drivers/tty/serial/8250/8250_dw.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index c89ae4581378..6ee55a2d47bb 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -201,8 +201,31 @@ static unsigned int dw8250_serial_in32be(struct uart_port *p, int offset) static int dw8250_handle_irq(struct uart_port *p) { + struct uart_8250_port *up = up_to_u8250p(p); struct dw8250_data *d = p->private_data; unsigned int iir = p->serial_in(p, UART_IIR); + unsigned int status; + unsigned long flags; + + /* + * There are ways to get Designware-based UARTs into a state where + * they are asserting UART_IIR_RX_TIMEOUT but there is no actual + * data available. If we see such a case then we'll do a bogus + * read. If we don't do this then the "RX TIMEOUT" interrupt will + * fire forever. + * + * This problem has only been observed so far when not in DMA mode + * so we limit the workaround only to non-DMA mode. + */ + if (!up->dma && ((iir & 0x3f) == UART_IIR_RX_TIMEOUT)) { + spin_lock_irqsave(&p->lock, flags); + status = p->serial_in(p, UART_LSR); + + if (!(status & (UART_LSR_DR | UART_LSR_BI))) + (void) p->serial_in(p, UART_RX); + + spin_unlock_irqrestore(&p->lock, flags); + } if (serial8250_handle_irq(p, iir)) return 1; |