From patchwork Mon Mar 14 09:14:32 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Ilpo_J=C3=A4rvinen?= X-Patchwork-Id: 551170 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31314C433F5 for ; Mon, 14 Mar 2022 09:14:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237895AbiCNJQA (ORCPT ); Mon, 14 Mar 2022 05:16:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47806 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237892AbiCNJP7 (ORCPT ); Mon, 14 Mar 2022 05:15:59 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 096F43ED3A; Mon, 14 Mar 2022 02:14:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1647249290; x=1678785290; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=tek9pvUQ8wIJl35VuH25V3YzoAX1Jt0Th31Nu4xv2nI=; b=FgbKYYTflQBXhV6z6qK9fn7th8zg/svYGcOtiKtj1y/YjHVF/SRW9Bqg ag+HN3oaQb9yiHSwPSFREzAVzoPJAxkvbfBkXqgP8GqUzwWeYXBTrU70u k7ByhR4AEcV6TvLjkHzcaCw8tDL/4MJZjjL5F3M+rlFbZnoj66qIjzthe 84KVh+6b0BLdORGCbENeTpzn76yBPG5TAnm4ipUa+DJFV2oTJ77OoGRv3 1AKEnPWEh2VnbizJTtpjaJ/Esv5ryAUXsWQmXUdYJYcHZD7n1yde8qurI qZAMy/Kifmt8smQK5aU1aLjpqVppRaVndaUjcDIsfL9vtf5Z4O9IlVTv/ w==; X-IronPort-AV: E=McAfee;i="6200,9189,10285"; a="319201111" X-IronPort-AV: E=Sophos;i="5.90,180,1643702400"; d="scan'208";a="319201111" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2022 02:14:49 -0700 X-IronPort-AV: E=Sophos;i="5.90,180,1643702400"; d="scan'208";a="556322465" Received: from srafikbh-mobl1.gar.corp.intel.com (HELO ijarvine-MOBL2.ger.corp.intel.com) ([10.252.54.232]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2022 02:14:42 -0700 From: =?utf-8?q?Ilpo_J=C3=A4rvinen?= To: linux-serial@vger.kernel.org, Greg KH , Jiri Slaby Cc: linux-kernel@vger.kernel.org, Johan Hovold , Andy Shevchenko , Miquel Raynal , Lukas Wunner , Heikki Krogerus , Gilles Buloz , =?utf-8?q?Ilpo_J=C3=A4rvinen?= Subject: [PATCH 1/1] serial: 8250: fix XOFF/XON sending when DMA is used Date: Mon, 14 Mar 2022 11:14:32 +0200 Message-Id: <20220314091432.4288-2-ilpo.jarvinen@linux.intel.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220314091432.4288-1-ilpo.jarvinen@linux.intel.com> References: <20220314091432.4288-1-ilpo.jarvinen@linux.intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org When 8250 UART is using DMA, x_char (XON/XOFF) is never sent to the wire. After this change, x_char is injected correctly. Create uart_xchar_out() helper for sending the x_char out and accounting related to it. It seems that almost every driver does these same steps with x_char. Except for 8250, however, almost all currently lack .serial_out so they cannot immediately take advantage of this new helper. The downside of this patch is that it might reintroduce the problems some devices faced with mixed DMA/non-DMA transfer which caused revert f967fc8f165f (Revert "serial: 8250_dma: don't bother DMA with small transfers"). However, the impact should be limited to cases with XON/XOFF (that didn't work with DMA capable devices to begin with so this problem is not very likely to cause a major issue, if any at all). Reported-by: Gilles Buloz Tested-by: Gilles Buloz Fixes: 9ee4b83e51f74 ("serial: 8250: Add support for dmaengine") Signed-off-by: Ilpo Järvinen --- drivers/tty/serial/8250/8250_dma.c | 11 ++++++++++- drivers/tty/serial/8250/8250_port.c | 4 +--- drivers/tty/serial/serial_core.c | 14 ++++++++++++++ include/linux/serial_core.h | 2 ++ 4 files changed, 27 insertions(+), 4 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c index 890fa7ddaa7f..b3c3f7e5851a 100644 --- a/drivers/tty/serial/8250/8250_dma.c +++ b/drivers/tty/serial/8250/8250_dma.c @@ -64,10 +64,19 @@ int serial8250_tx_dma(struct uart_8250_port *p) struct uart_8250_dma *dma = p->dma; struct circ_buf *xmit = &p->port.state->xmit; struct dma_async_tx_descriptor *desc; + struct uart_port *up = &p->port; int ret; - if (dma->tx_running) + if (dma->tx_running) { + if (up->x_char) { + dmaengine_pause(dma->txchan); + uart_xchar_out(up, UART_TX); + dmaengine_resume(dma->txchan); + } return 0; + } else if (up->x_char) { + uart_xchar_out(up, UART_TX); + } if (uart_tx_stopped(&p->port) || uart_circ_empty(xmit)) { /* We have been called from __dma_tx_complete() */ diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 3b12bfc1ed67..63e9bc6fce06 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1799,9 +1799,7 @@ void serial8250_tx_chars(struct uart_8250_port *up) int count; if (port->x_char) { - serial_out(up, UART_TX, port->x_char); - port->icount.tx++; - port->x_char = 0; + uart_xchar_out(port, UART_TX); return; } if (uart_tx_stopped(port)) { diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 0db90be4c3bc..f67540ae2a88 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -644,6 +644,20 @@ static void uart_flush_buffer(struct tty_struct *tty) tty_port_tty_wakeup(&state->port); } +/* + * This function performs low-level write of high-priority XON/XOFF + * character and accounting for it. + * + * Requires uart_port to implement .serial_out(). + */ +void uart_xchar_out(struct uart_port *uport, int offset) +{ + serial_port_out(uport, offset, uport->x_char); + uport->icount.tx++; + uport->x_char = 0; +} +EXPORT_SYMBOL_GPL(uart_xchar_out); + /* * This function is used to send a high-priority XON/XOFF character to * the device diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index c58cc142d23f..8c32935e1059 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -458,6 +458,8 @@ extern void uart_handle_cts_change(struct uart_port *uport, extern void uart_insert_char(struct uart_port *port, unsigned int status, unsigned int overrun, unsigned int ch, unsigned int flag); +void uart_xchar_out(struct uart_port *uport, int offset); + #ifdef CONFIG_MAGIC_SYSRQ_SERIAL #define SYSRQ_TIMEOUT (HZ * 5)