From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754548AbbKMIfY (ORCPT ); Fri, 13 Nov 2015 03:35:24 -0500 Received: from mail-wm0-f47.google.com ([74.125.82.47]:35564 "EHLO mail-wm0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754040AbbKMIfW (ORCPT ); Fri, 13 Nov 2015 03:35:22 -0500 MIME-Version: 1.0 In-Reply-To: <56449596.5020109@hurleysoftware.com> References: <1446890976-1817-1-git-send-email-matwey@sai.msu.ru> <1446890976-1817-3-git-send-email-matwey@sai.msu.ru> <56421759.8070103@hurleysoftware.com> <56449596.5020109@hurleysoftware.com> From: "Matwey V. Kornilov" Date: Fri, 13 Nov 2015 11:35:01 +0300 X-Google-Sender-Auth: ZUdQ8UyEtLjV6SIqXMcDnLGAzuM Message-ID: Subject: Re: [PATCH v2 3/3] tty: Add software emulated RS485 support for 8250 To: Peter Hurley Cc: Greg KH , jslaby@suse.com, linux-serial@vger.kernel.org, linux-kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2015-11-12 16:35 GMT+03:00 Peter Hurley : > On 11/12/2015 07:34 AM, Matwey V. Kornilov wrote: >> 2015-11-10 19:12 GMT+03:00 Peter Hurley : >>> On 11/07/2015 05:09 AM, Matwey V. Kornilov wrote: >>>> Implementation of software emulation of RS485 direction handling is based >>>> on omap-serial driver. It is acts as the following. At transmission start, >>>> RTS is set (if required) and receiver is off (if required). At transmission >>>> stop, RTS is set (if required) and fifo is flushed. >>>> >>>> Signed-off-by: Matwey V. Kornilov >>>> --- >>>> drivers/tty/serial/8250/8250_port.c | 32 ++++++++++++++++++++++++++++++++ >>>> 1 file changed, 32 insertions(+) >>>> >>>> diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c >>>> index 52d82d2..a9291f7 100644 >>>> --- a/drivers/tty/serial/8250/8250_port.c >>>> +++ b/drivers/tty/serial/8250/8250_port.c >>>> @@ -559,7 +559,37 @@ static void serial8250_rpm_put_tx(struct uart_8250_port *p) >>>> pm_runtime_mark_last_busy(p->port.dev); >>>> pm_runtime_put_autosuspend(p->port.dev); >>>> } >>>> +static void serial8250_stop_rx(struct uart_port *port); >>>> +static void serial8250_rs485_start_tx(struct uart_8250_port *p) >>>> +{ >>>> + if (p->capabilities & UART_CAP_HW485 || !(p->port.rs485.flags & SER_RS485_ENABLED)) >>>> + return; >>>> + >>>> + if (p->port.rs485.flags & SER_RS485_RTS_ON_SEND) { >>>> + serial_port_out(&p->port, UART_MCR, UART_MCR_RTS); >>> >>> The SER_RS485_RTS_ON_SEND bit is supposed to be the logic level of RTS, >>> so RTS should be driven to either 0 or 1 here (not just to 1). >> >> By the way, I've found that p->mcr caches MCR inconsistently. Is it >> supposed to be so? Or p->mcr is not for caching? > > Not for caching; it's for modal settings (eg., AFE) that the 8250 port > driver needs to merge in when changing mctrl bits (DTR/RTS/etc). > > The serial core caches the mctrl bits in uart_port->mctrl, but IMO > it would be simpler to always set/clear RTS here (rather than like > the omap-serial driver where it checks the gpio value first). > > Is the assumption that userspace will not perform conflicting > operations, such as ioctl(TIOCMSET) or ioctl(TCSETSx), with RS485 enabled? I've sent v3 series and put all RTS related stuff into separate functions. Could you please continue this discussion in "v3 5/5"? TIOCMGET should work correctly now, because it reads register. I am not sure that TIOCMSET should be limited somehow, user knows better what he wants. > Regards, > Peter Hurley > -- With best regards, Matwey V. Kornilov. Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382