From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69150C49EA6 for ; Thu, 24 Jun 2021 12:55:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 44794613F3 for ; Thu, 24 Jun 2021 12:55:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231857AbhFXM6K (ORCPT ); Thu, 24 Jun 2021 08:58:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:44550 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230236AbhFXM6J (ORCPT ); Thu, 24 Jun 2021 08:58:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A61EB61407; Thu, 24 Jun 2021 12:55:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1624539350; bh=vy27O8JHG86KjCPMaZ8nNLDj35x7lCCYEq8JX2Xp62E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WibYVJLWPuC17dxXRiJ/EJVGl8V8CbfngWxp8RGBc0x1M60+UijMx72/gokL0k/pL Run4vxeWl0vC/Xxia7yw4dIT6aDnGlfzTXlUse2FZfKuzegx2DCXnLVtPo5nIQOz3q CzUf5ahKm+Hp3HLBkOCcpjqVnqKlyAIhTefOUp6I= Date: Thu, 24 Jun 2021 14:55:48 +0200 From: Greg KH To: Lino Sanfilippo Cc: linux@armlinux.org.uk, jirislaby@kernel.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] serial: amba-pl011: add RS485 support Message-ID: References: <20210618145153.1906-1-LinoSanfilippo@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210618145153.1906-1-LinoSanfilippo@gmx.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 18, 2021 at 04:51:53PM +0200, Lino Sanfilippo wrote: > Add basic support for RS485: Provide a callback to configure RS485 > settings. Handle the RS485 specific part in the functions > pl011_rs485_tx_start() and pl011_rs485_tx_stop() which extend the generic > start/stop callbacks. > Beside via IOCTL from userspace RS485 can be enabled by means of the > device tree property "rs485-enabled-at-boot-time". > > Signed-off-by: Lino Sanfilippo > --- > This patch applies against Gregs tty-testing branch and was tested on a > Raspberry Pi CM3. > > Changes in V2: > - clamp RTS delays to 100ms as suggested by Jiri Slaby > - instead of counting bits "by hand" use the new function tty_get_frame_size() > (also suggested by Jiri) > - use the term RS485 consistently in the commit message > - remove one blank line > > > drivers/tty/serial/amba-pl011.c | 152 +++++++++++++++++++++++++++++++- > 1 file changed, 150 insertions(+), 2 deletions(-) > > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c > index e14f3378b8a0..92c6b08d56fb 100644 > --- a/drivers/tty/serial/amba-pl011.c > +++ b/drivers/tty/serial/amba-pl011.c > @@ -265,6 +265,8 @@ struct uart_amba_port { > unsigned int old_cr; /* state during shutdown */ > unsigned int fixed_baud; /* vendor-set fixed baud rate */ > char type[12]; > + bool rs485_tx_started; > + unsigned int rs485_tx_drain_interval; /* usecs */ > #ifdef CONFIG_DMA_ENGINE > /* DMA stuff */ > bool using_tx_dma; > @@ -275,6 +277,8 @@ struct uart_amba_port { > #endif > }; > > +static unsigned int pl011_tx_empty(struct uart_port *port); > + > static unsigned int pl011_reg_to_offset(const struct uart_amba_port *uap, > unsigned int reg) > { > @@ -1282,6 +1286,34 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap) > #define pl011_dma_flush_buffer NULL > #endif > > +static int pl011_rs485_tx_stop(struct uart_amba_port *uap) > +{ > + struct uart_port *port = &uap->port; > + u32 cr; > + > + /* Wait until hardware tx queue is empty */ > + while (!pl011_tx_empty(port)) > + udelay(uap->rs485_tx_drain_interval); No way out if the hardware doesn't ever empty? Shouldn't you have an "upper bound" on this loop somehow? > + > + if (port->rs485.delay_rts_after_send) > + mdelay(port->rs485.delay_rts_after_send); > + > + cr = pl011_read(uap, REG_CR); > + > + if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND) > + cr &= ~UART011_CR_RTS; > + else > + cr |= UART011_CR_RTS; Blank line here please. > + /* Disable the transmitter and reenable the transceiver */ > + cr &= ~UART011_CR_TXE; > + cr |= UART011_CR_RXE; > + pl011_write(cr, uap, REG_CR); > + > + uap->rs485_tx_started = false; > + > + return 0; Why does this function return a value if it can not fail and you do not check the return value of it? > +} > + > static void pl011_stop_tx(struct uart_port *port) > { > struct uart_amba_port *uap = > @@ -1290,6 +1322,9 @@ static void pl011_stop_tx(struct uart_port *port) > uap->im &= ~UART011_TXIM; > pl011_write(uap->im, uap, REG_IMSC); > pl011_dma_tx_stop(uap); > + > + if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started) > + pl011_rs485_tx_stop(uap); So, no check :( > } > > static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq); > @@ -1380,6 +1415,31 @@ static bool pl011_tx_char(struct uart_amba_port *uap, unsigned char c, > return true; > } > > +static void pl011_rs485_tx_start(struct uart_amba_port *uap) > +{ > + struct uart_port *port = &uap->port; > + u32 cr; > + > + /* Enable transmitter */ > + cr = pl011_read(uap, REG_CR); > + cr |= UART011_CR_TXE; Blank line please. > + /* Disable receiver if half-duplex */ > + if (!(port->rs485.flags & SER_RS485_RX_DURING_TX)) > + cr &= ~UART011_CR_RXE; > + > + if (port->rs485.flags & SER_RS485_RTS_ON_SEND) > + cr &= ~UART011_CR_RTS; > + else > + cr |= UART011_CR_RTS; > + > + pl011_write(cr, uap, REG_CR); > + > + if (port->rs485.delay_rts_before_send) > + mdelay(port->rs485.delay_rts_before_send); > + > + uap->rs485_tx_started = true; > +} > + > /* Returns true if tx interrupts have to be (kept) enabled */ > static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq) > { > @@ -1397,6 +1457,10 @@ static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq) > return false; > } > > + if ((uap->port.rs485.flags & SER_RS485_ENABLED) && > + !uap->rs485_tx_started) > + pl011_rs485_tx_start(uap); > + > /* If we are using DMA mode, try to send some characters. */ > if (pl011_dma_tx_irq(uap)) > return true; > @@ -1542,6 +1606,9 @@ static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl) > container_of(port, struct uart_amba_port, port); > unsigned int cr; > > + if (port->rs485.flags & SER_RS485_ENABLED) > + mctrl &= ~TIOCM_RTS; > + > cr = pl011_read(uap, REG_CR); > > #define TIOCMBIT(tiocmbit, uartbit) \ > @@ -1763,7 +1830,17 @@ static int pl011_startup(struct uart_port *port) > > /* restore RTS and DTR */ > cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR); > - cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE; > + cr |= UART01x_CR_UARTEN | UART011_CR_RXE; > + > + if (port->rs485.flags & SER_RS485_ENABLED) { > + if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND) > + cr &= ~UART011_CR_RTS; > + else > + cr |= UART011_CR_RTS; > + } else { > + cr |= UART011_CR_TXE; > + } > + > pl011_write(cr, uap, REG_CR); > > spin_unlock_irq(&uap->port.lock); > @@ -1864,6 +1941,9 @@ static void pl011_shutdown(struct uart_port *port) > > pl011_dma_shutdown(uap); > > + if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started) > + pl011_rs485_tx_stop(uap); > + > free_irq(uap->port.irq, uap); > > pl011_disable_uart(uap); > @@ -1941,6 +2021,7 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios, > unsigned int lcr_h, old_cr; > unsigned long flags; > unsigned int baud, quot, clkdiv; > + unsigned int bits; > > if (uap->vendor->oversampling) > clkdiv = 8; > @@ -1991,18 +2072,29 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios, > if (uap->fifosize > 1) > lcr_h |= UART01x_LCRH_FEN; > > + bits = tty_get_frame_size(termios->c_cflag); > + > spin_lock_irqsave(&port->lock, flags); > > /* > * Update the per-port timeout. > */ > uart_update_timeout(port, termios->c_cflag, baud); Blank line > + /* > + * Calculate the approximated time it takes to transmit one character > + * with the given baud rate. We use this as the poll interval when we > + * wait for the tx queue to empty. > + */ > + uap->rs485_tx_drain_interval = (bits * 1000 * 1000) / baud; > > pl011_setup_status_masks(port, termios); > > if (UART_ENABLE_MS(port, termios->c_cflag)) > pl011_enable_ms(port); > > + if (port->rs485.flags & SER_RS485_ENABLED) > + termios->c_cflag &= ~CRTSCTS; > + > /* first, disable everything */ > old_cr = pl011_read(uap, REG_CR); > pl011_write(0, uap, REG_CR); > @@ -2124,6 +2216,40 @@ static int pl011_verify_port(struct uart_port *port, struct serial_struct *ser) > return ret; > } > > +static int pl011_rs485_config(struct uart_port *port, > + struct serial_rs485 *rs485) > +{ > + struct uart_amba_port *uap = > + container_of(port, struct uart_amba_port, port); > + > + /* pick sane settings if the user hasn't */ > + if (!!(rs485->flags & SER_RS485_RTS_ON_SEND) == Why the !! in an if statement? > + !!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) { Same here, why? > + rs485->flags |= SER_RS485_RTS_ON_SEND; > + rs485->flags &= ~SER_RS485_RTS_AFTER_SEND; > + } > + /* clamp the delays to [0, 100ms] */ > + rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U); > + rs485->delay_rts_after_send = min(rs485->delay_rts_after_send, 100U); > + memset(rs485->padding, 0, sizeof(rs485->padding)); > + > + if (port->rs485.flags & SER_RS485_ENABLED) > + pl011_rs485_tx_stop(uap); > + > + /* Set new configuration */ > + port->rs485 = *rs485; Blank line please. > + /* Make sure auto RTS is disabled */ > + if (port->rs485.flags & SER_RS485_ENABLED) { > + u32 cr = pl011_read(uap, REG_CR); > + > + cr &= ~UART011_CR_RTSEN; > + pl011_write(cr, uap, REG_CR); > + port->status &= ~UPSTAT_AUTORTS; > + } > + > + return 0; > +} > + thanks, greg k-h