On 08/07/2014 01:12 PM, Greg Kroah-Hartman wrote: > On Thu, Aug 07, 2014 at 12:16:59PM -0400, Murali Karicheri wrote: >> On 08/07/2014 11:29 AM, Peter Hurley wrote: >>> On 05/01/2014 03:04 PM, Murali Karicheri wrote: >>>> 8250 uart driver currently supports only software assisted hw flow >>>> control. The software assisted hw flow control maintains a hw_stopped >>>> flag in the tty structure to stop and start transmission and use modem >>>> status interrupt for the event to drive the handshake signals. This is >>>> not needed if hw has flow control capabilities. This patch adds a >>>> DT attribute for enabling hw flow control for a uart port. Also skip >>>> stop and start if this flag is present in flag field of the port >>>> structure. >>>> >>>> Signed-off-by: Murali Karicheri<m-karicheri2@xxxxxx> >>>> >>>> CC: Rob Herring<robh+dt@xxxxxxxxxx> >>>> CC: Pawel Moll<pawel.moll@xxxxxxx> >>>> CC: Mark Rutland<mark.rutland@xxxxxxx> >>>> CC: Ian Campbell<ijc+devicetree@xxxxxxxxxxxxxx> >>>> CC: Kumar Gala<galak@xxxxxxxxxxxxxx> >>>> CC: Randy Dunlap<rdunlap@xxxxxxxxxxxxx> >>>> CC: Greg Kroah-Hartman<gregkh@xxxxxxxxxxxxxxxxxxx> >>>> CC: Jiri Slaby<jslaby@xxxxxxx> >>>> CC: Santosh Shilimkar<santosh.shilimkar@xxxxxx> >>>> --- >>>> .../devicetree/bindings/serial/of-serial.txt | 1 + >>>> drivers/tty/serial/8250/8250_core.c | 6 ++++-- >>>> drivers/tty/serial/of_serial.c | 4 ++++ >>>> drivers/tty/serial/serial_core.c | 12 +++++++++--- >>>> 4 files changed, 18 insertions(+), 5 deletions(-) >>>> >>> [...] >>> >>>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c >>>> index b68550d..851707a 100644 >>>> --- a/drivers/tty/serial/serial_core.c >>>> +++ b/drivers/tty/serial/serial_core.c >>>> @@ -174,8 +174,12 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state, >>>> if (tty->termios.c_cflag& CBAUD) >>>> uart_set_mctrl(uport, TIOCM_RTS | TIOCM_DTR); >>>> } >>>> - >>>> - if (tty_port_cts_enabled(port)) { >>>> + /* >>>> + * if hw support flow control without software intervention, >>>> + * then skip the below check >>>> + */ >>>> + if (tty_port_cts_enabled(port)&& >>>> + !(uport->flags& UPF_HARD_FLOW)) { >>>> spin_lock_irq(&uport->lock); >>>> if (!(uport->ops->get_mctrl(uport)& TIOCM_CTS)) >>>> tty->hw_stopped = 1; >>>> @@ -2772,7 +2776,9 @@ void uart_handle_cts_change(struct uart_port *uport, unsigned int status) >>>> >>>> uport->icount.cts++; >>>> >>>> - if (tty_port_cts_enabled(port)) { >>>> + /* skip below code if the hw flow control is supported */ >>>> + if (tty_port_cts_enabled(port)&& >>>> + !(uport->flags& UPF_HARD_FLOW)) { >>> Why is a modem status interrupt being generated for DCTS >>> if autoflow control is enabled? >>> >>> This should be: >>> >>> WARN_ON_ONCE(uport->flags& UPF_HARD_FLOW); >>> >>> to indicate a mis-configured driver/device. >> This patch is already merged to the upstream branch and if you see any >> issue, please >> post a patch for review. > > If someone points out a problem in a patch of yours that is accepted > upstream, it is nice to provide a fix, otherwise I will just revert it > upstream, as it looks to be incorrect. > > So, should I just revert it? Greg, As I look this patch over further, this should just be reverted. 1. The patch enables UPF_HARD_FLOW, but provides no throttle() and unthrottle() methods for 8250, which is guaranteed to blow-up when either uart_throttle() or uart_unthrottle() is called. 2. The patch adds capabilities which already exist, namely UART_CAP_AFE. Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html