From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752152AbbKLMfO (ORCPT ); Thu, 12 Nov 2015 07:35:14 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:34970 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751428AbbKLMfM (ORCPT ); Thu, 12 Nov 2015 07:35:12 -0500 MIME-Version: 1.0 In-Reply-To: <56421759.8070103@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> From: "Matwey V. Kornilov" Date: Thu, 12 Nov 2015 15:34:51 +0300 X-Google-Sender-Auth: qmLM5KsLMmrfqmTYAq5Dc3MYIIE 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 2015-11-10 19:12 GMT+03:00 Peter Hurley : > Hi Matwey, > > I noticed 3 other issues here; see below. > > 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? > >> + if (p->port.rs485.delay_rts_before_send > 0) >> + mdelay(p->port.rs485.delay_rts_before_send); >> + } >> + if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) >> + serial8250_stop_rx(&p->port); >> +} >> +static void serial8250_rs485_stop_tx(struct uart_8250_port *p) >> +{ >> + if (p->capabilities & UART_CAP_HW485 || !(p->port.rs485.flags & SER_RS485_ENABLED)) >> + return; > > Unlike omap-serial, the 8250 stop_tx() will trigger _before_ the transmitter > is drained. Some mechanism is required to defer until the transmitter > is empty. > >> + if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) { >> + if (p->port.rs485.delay_rts_after_send > 0) >> + mdelay(p->port.rs485.delay_rts_after_send); >> + serial_port_out(&p->port, UART_MCR, UART_MCR_RTS); > > As with the SER_RS485_RTS_ON_SEND, RTS should be driven to either 0 or 1 here > as well (not just to 1). > > Regards, > Peter Hurley > >> + } >> + /* >> + * Empty the RX FIFO, we are not interested in anything >> + * received during the half-duplex transmission. >> + */ >> + if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) >> + serial8250_clear_fifos(p); >> +} >> /* >> * IER sleep support. UARTs which have EFRs need the "extended >> * capability" bit enabled. Note that on XR16C850s, we need to >> @@ -1309,6 +1339,7 @@ static void serial8250_stop_tx(struct uart_port *port) >> up->acr |= UART_ACR_TXDIS; >> serial_icr_write(up, UART_ACR, up->acr); >> } >> + serial8250_rs485_stop_tx(up); >> serial8250_rpm_put(up); >> } >> >> @@ -1317,6 +1348,7 @@ static void serial8250_start_tx(struct uart_port *port) >> struct uart_8250_port *up = up_to_u8250p(port); >> >> serial8250_rpm_get_tx(up); >> + serial8250_rs485_start_tx(up); >> >> if (up->dma && !up->dma->tx_dma(up)) >> return; >> > -- With best regards, Matwey V. Kornilov. Sternberg Astronomical Institute, Lomonosov Moscow State University, Russia 119991, Moscow, Universitetsky pr-k 13, +7 (495) 9392382