| Message ID | 1425472054-7543-3-git-send-email-Dave.Martin@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Mar 04, 2015 at 12:27:34PM +0000, Dave Martin wrote: > Getting the TX IRQ re-asserted from scratch can be inefficient in > some setups. > > This patch avoids clearing the TX IRQ across pl011_shutdown()... > pl011_startup(), so that if the port is closed and reopened, the > IRQ will still work afterwards without having to bootstrap it again. So if a port is being used as the console, we end up spraying the system with transmit interrupts? This can't be right.
On Thu, Mar 12, 2015 at 11:04:41AM +0000, Russell King - ARM Linux wrote: > On Wed, Mar 04, 2015 at 12:27:34PM +0000, Dave Martin wrote: > > Getting the TX IRQ re-asserted from scratch can be inefficient in > > some setups. > > > > This patch avoids clearing the TX IRQ across pl011_shutdown()... > > pl011_startup(), so that if the port is closed and reopened, the > > IRQ will still work afterwards without having to bootstrap it again. > > So if a port is being used as the console, we end up spraying the system > with transmit interrupts? This can't be right. Nope, if the port is not open theough serial_core then TXIS remains asserted but is masked off in IMSC. This should be just the same as the way we avoid a screaming TX interrupt when the port *is* open but the transmitter is idle. My commit message could have explained that better... Cheers ---Dave
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 69910f7..92783fc 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1676,9 +1676,6 @@ static int pl011_startup(struct uart_port *port) writew(uap->vendor->ifls, uap->port.membase + UART011_IFLS); - /* Assume that TX IRQ doesn't work until we see one: */ - uap->tx_irq_seen = 0; - spin_lock_irq(&uap->port.lock); /* restore RTS and DTR */ @@ -1742,7 +1739,7 @@ static void pl011_shutdown(struct uart_port *port) spin_lock_irq(&uap->port.lock); uap->im = 0; writew(uap->im, uap->port.membase + UART011_IMSC); - writew(0xffff, uap->port.membase + UART011_ICR); + writew(0xffff & ~UART011_TXIS, uap->port.membase + UART011_ICR); spin_unlock_irq(&uap->port.lock); pl011_dma_shutdown(uap);
Getting the TX IRQ re-asserted from scratch can be inefficient in some setups. This patch avoids clearing the TX IRQ across pl011_shutdown()... pl011_startup(), so that if the port is closed and reopened, the IRQ will still work afterwards without having to bootstrap it again. The TX IRQ continues to be masked in IMSC when the UART is not in use. Signed-off-by: Dave Martin <Dave.Martin@arm.com> --- drivers/tty/serial/amba-pl011.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)