> -----Original Message----- > From: Chanho Min [mailto:chanho0207@xxxxxxxxx] > Sent: Monday, February 27, 2012 6:30 PM > To: Russell King; Alan Cox; Greg Kroah-Hartman; Linus Walleij; Shreshtha > Kumar Sahu; Kim, Jong-Sung > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx > Subject: [PATCH] Clear previous interrupts after fifo is disabled > > This is another workaroud of 'https://lkml.org/lkml/2012/1/17/104' > with additional analysis.Bootloader can transfer control to kernel and there > are some pending interrupts. In this case, RXFE of the flag register is set > by clearing FEN(LCRH) even if rx data remains in the fifo. It seems that the > fifo's status is initiailized. Interrupt handler can not get any data from > data register because of the below break condtion. > > pl011_fifo_to_tty > while (max_count--) { > if (status & UART01x_FR_RXFE) > break; > > Then, Rx interrupt is never cleared. cpu is looping in ISR. System is hang. > If we don't guarantee that no interrupt is pended until fifo is disabled by > calling 'writew(0, uap->port.membase + uap->lcrh_rx)', this misbehave of the > interrupt handelr can be occurred. So, All pending interrupts should be > cleared just after fifo is disabled under the protection from interrupt. > Also,'clear error interrupts' routine can be removed becuase all interrupts > are cleared before. > > Signed-off-by: Chanho Min <chanho.min@xxxxxxx> May I suggest another approach at this point? The problematic condition you reported could be considered as an exceptional Rx interrupt status. So, we can handle it in the Rx ISR. Simply: diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 6800f5f..5b5358705 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -224,6 +224,10 @@ static int pl011_fifo_to_tty(struct uart_amba_port *uap) uart_insert_char(&uap->port, ch, UART011_DR_OE, ch, flag); } + /* RXIS but RXFE? Just clear the interrupt */ + if(unlikely(fifotaken == 0)) + writew(UART011_RXIS, uap->port.membase + UART01x_ICR); + return fifotaken; } -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
