Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751193AbbKHKwn (ORCPT ); Sun, 8 Nov 2015 05:52:43 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:35085 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750716AbbKHKwj (ORCPT ); Sun, 8 Nov 2015 05:52:39 -0500 MIME-Version: 1.0 In-Reply-To: <563E20DE.7000209@hurleysoftware.com> References: <1446890976-1817-1-git-send-email-matwey@sai.msu.ru> <1446890976-1817-3-git-send-email-matwey@sai.msu.ru> <563E20DE.7000209@hurleysoftware.com> From: "Matwey V. Kornilov" Date: Sun, 8 Nov 2015 13:52:19 +0300 X-Google-Sender-Auth: v2DXX0E8tkJei6segxNWuazstwQ 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 Content-Length: 4045 Lines: 111 2015-11-07 19:03 GMT+03:00 Peter Hurley : > Hi Matwey, > > 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. > > Comments below. > >> 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); >> } > > Newline req'd here. > >> +static void serial8250_stop_rx(struct uart_port *port); > > You can eliminate this forward decl by relocating serial8250_stop_rx() to here > (in a separate patch). > >> +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); >> + if (p->port.rs485.delay_rts_before_send > 0) >> + mdelay(p->port.rs485.delay_rts_before_send); > > So irqs are off for x msecs, and this cpu can't be used for anything else now? > I think this needs to be solved differently; maybe with a timer? Call of serial8250_start_tx is wrapped with spin_lock_irq in serial_core.c:2154 I've tried to use msleep instead of mdelay but got "BUG: scheduling while atomic". > >> + } >> + if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) >> + serial8250_stop_rx(&p->port); >> +} > > Newline req'd here. > >> +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; >> >> + 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); > > Same issue with irqs off. > >> + serial_port_out(&p->port, UART_MCR, UART_MCR_RTS); >> + } >> + /* >> + * 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/