On Fri, Sep 01, 2017 at 09:48:15AM -0500, Russell Enderby wrote: > Issue where unprintable characters can occur or output is cut off over > the serial uart / linux console depending on timing. > > Problem occurs when changing the serial baud rate when setting up the > new console.The bcm63xx driver does a disable and flush of the uart tx > fifo while there is data still in the tx fifo. > > If the tx fifo still has data it is trying to send out, we need to wait > until it is empty before disabling and flushing the uart. > > When we now go to change the uart parameters including speed we check > if there is data currently in the tx fifo.If there is was mdelay(10) > and check again.If it tries 3 times and still has data in it we just > continue and sacrifice the tx fifo buffer. > > A cleaner and more preferred approach would be to remove : > - spin_lock_irqsave() > - bcm_uart_disable() > - bcm_uart_flush() > > However it is not clear if the author put those in to fix another > underlying issue.As a result this solution is a safer approach. > > BEFORE FIX > [0.306000] 14e00520.serial: ttyS0 at MMIO 0x14e00520 (irq = 9, base_baud = 1687500) is a° 0.315000] console[ttyS0] enabled > > AFTER FIX > [0.315000] 14e00520.serial: ttyS0 at MMIO 0x14e00520 (irq = 9, base_baud = 1687500) is a bcm63xx_uart > [0.334000] console[ttyS0] enabled > > Signed-off-by: Russell Enderby <rte@xxxxxxx> > --- > drivers/tty/serial/bcm63xx_uart.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/tty/serial/bcm63xx_uart.c b/drivers/tty/serial/bcm63xx_uart.c > index 2ea2763..8c48c37 100644 > --- a/drivers/tty/serial/bcm63xx_uart.c > +++ b/drivers/tty/serial/bcm63xx_uart.c > @@ -511,11 +511,9 @@ static void bcm_uart_set_termios(struct uart_port *port, > > spin_lock_irqsave(&port->lock, flags); > > - /*_ Drain the hot tub fully before we power it off for the winter. */ > + /* Drain the hot tub fully before we power it off for the winter. */ > for (tries = 3; !bcm_uart_tx_empty(port) && tries; tries--) > mdelay(10); > - if (!tries) > - printk(port->dev, "Unable to drain serial transmitter.\n"); > > /* disable uart while changing speed */ > bcm_uart_disable(port); Patch does not apply at all as you made it against a previous version of your patches. And I'm not going to apply your old patches, they were incorrect... -- 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
