From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932674AbaHGRZe (ORCPT ); Thu, 7 Aug 2014 13:25:34 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:43964 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932404AbaHGRZb (ORCPT ); Thu, 7 Aug 2014 13:25:31 -0400 X-Greylist: delayed 6967 seconds by postgrey-1.27 at vger.kernel.org; Thu, 07 Aug 2014 13:25:31 EDT Message-ID: <53E3B67E.80705@hurleysoftware.com> Date: Thu, 07 Aug 2014 13:25:18 -0400 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Greg Kroah-Hartman , Murali Karicheri CC: devicetree@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Randy Dunlap , Jiri Slaby , Santosh Shilimkar Subject: Re: [PATCH v2] serial: uart: add hw flow control support configuration References: <1398971093-17164-1-git-send-email-m-karicheri2@ti.com> <53E39B44.60406@hurleysoftware.com> <53E3A67B.6070709@ti.com> <20140807171254.GA13097@kroah.com> In-Reply-To: <20140807171254.GA13097@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>>> >>>> CC: Rob Herring >>>> CC: Pawel Moll >>>> CC: Mark Rutland >>>> CC: Ian Campbell >>>> CC: Kumar Gala >>>> CC: Randy Dunlap >>>> CC: Greg Kroah-Hartman >>>> CC: Jiri Slaby >>>> CC: Santosh Shilimkar >>>> --- >>>> .../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