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> --- drivers/tty/serial/amba-pl011.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 6800f5f..8b5a824 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1397,7 +1397,11 @@ static int pl011_startup(struct uart_port *port) writew(cr, uap->port.membase + UART011_CR); writew(0, uap->port.membase + UART011_FBRD); writew(1, uap->port.membase + UART011_IBRD); + spin_lock_irq(&uap->port.lock); writew(0, uap->port.membase + uap->lcrh_rx); + /* Clear all pending interrupts. */ + writew(0xffff, uap->port.membase + UART011_ICR); + spin_unlock_irq(&uap->port.lock); if (uap->lcrh_tx != uap->lcrh_rx) { int i; /* @@ -1417,10 +1421,6 @@ static int pl011_startup(struct uart_port *port) cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE; writew(cr, uap->port.membase + UART011_CR); - /* Clear pending error interrupts */ - writew(UART011_OEIS | UART011_BEIS | UART011_PEIS | UART011_FEIS, - uap->port.membase + UART011_ICR); - /* * initialise the old status of the modem signals */ -- 1.7.0.4 -- 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
