From patchwork Mon Mar 16 16:19:54 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yoshihiro Kaneko X-Patchwork-Id: 6022861 X-Patchwork-Delegate: geert@linux-m68k.org Return-Path: X-Original-To: patchwork-linux-sh@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 1BCC99F2A9 for ; Mon, 16 Mar 2015 16:20:24 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 2C736201F2 for ; Mon, 16 Mar 2015 16:20:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 42B392017E for ; Mon, 16 Mar 2015 16:20:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933307AbbCPQUV (ORCPT ); Mon, 16 Mar 2015 12:20:21 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:33514 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933194AbbCPQUU (ORCPT ); Mon, 16 Mar 2015 12:20:20 -0400 Received: by pagr17 with SMTP id r17so69081424pag.0; Mon, 16 Mar 2015 09:20:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id; bh=q/HVLltV9oPhDIogsSQlhZmT9mUqZKaNB/eAcgS7Tks=; b=ANZstZKtliDmxogHLJIB2ydmiLDmE2N453Bpj87ODMI2Vvlm7LW1AHxplpr/8y2Nej uaD0JcX0Lmnqq6o7MCkW4pgnou6m/h0PSBuZA49VDNpPde34+qCbcuh5kQzPP6DDbtwo P10ywza6FwpiL14ZTuT+Ie1nrwW+MrKJFZsO9spbxMli0zt3VDYrQXSaVBai6SlXXFhK am0KRd0wtSS30hl+a+XufzP1/ixkEmUbZG23g3LCN+TK8polxZseqgvW0H4Cg6RUsPG9 Cys9sABktjcaJcSGONCmMP9BTJQvl5o7WOdnIOpK/FlMruScUulwjSEsStAOHaOQj1/J 79VA== X-Received: by 10.70.109.135 with SMTP id hs7mr112566965pdb.133.1426522820107; Mon, 16 Mar 2015 09:20:20 -0700 (PDT) Received: from localhost.localdomain (KD118152108246.ppp-bb.dion.ne.jp. [118.152.108.246]) by mx.google.com with ESMTPSA id sm5sm18111413pac.10.2015.03.16.09.20.18 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 16 Mar 2015 09:20:19 -0700 (PDT) From: Yoshihiro Kaneko To: linux-serial@vger.kernel.org Cc: Greg Kroah-Hartman , Simon Horman , Magnus Damm , linux-sh@vger.kernel.org Subject: [PATCH v2] serial: sh-sci: Update calculation of timeout for DMA Date: Tue, 17 Mar 2015 01:19:54 +0900 Message-Id: <1426522794-25845-1-git-send-email-ykaneko0929@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-sh-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, T_DKIM_INVALID, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Nobuhiro Iwamatsu The current calculation method in the case of 9600bps, rounding error occurs has become setting that occur timeout faster than the required time. When we use 9600bps, 32byte buffer, 10 bit (CS8) and 100 HZ, it becomes 3 jiffies (30msec). In fact it is necessary 33msec. This updates to the calculation that are not actually less than the value set by the rounding error. Also, this is nothing will be calculated value when there is no load. If there are a lot of case load, overrun error will occur immediately. This is by the buffer size to be calculated twice the DMA buffer, and add the change of setting a sufficient time-out value. Signed-off-by: Nobuhiro Iwamatsu Signed-off-by: Yoshihiro Kaneko --- This patch is based on the tty-next branch of Greg Kroah-Hartman's tty tree. v2 [Yoshihiro Kaneko] * fix indentation of a case statement. * wrap a too long line in the block comment. drivers/tty/serial/sh-sci.c | 40 +++++++++++++++++++++++++++++++--------- 1 file changed, 31 insertions(+), 9 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 5b50c79..bc6daf8 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1967,18 +1967,40 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios, #ifdef CONFIG_SERIAL_SH_SCI_DMA /* - * Calculate delay for 1.5 DMA buffers: see - * drivers/serial/serial_core.c::uart_update_timeout(). With 10 bits - * (CS8), 250Hz, 115200 baud and 64 bytes FIFO, the above function + * Calculate delay for 2 DMA buffers (4 FIFO). + * See drivers/serial/serial_core.c::uart_update_timeout(). With 10 + * bits (CS8), 250Hz, 115200 baud and 64 bytes FIFO, the above function * calculates 1 jiffie for the data plus 5 jiffies for the "slop(e)." - * Then below we calculate 3 jiffies (12ms) for 1.5 DMA buffers (3 FIFO - * sizes), but it has been found out experimentally, that this is not - * enough: the driver too often needlessly runs on a DMA timeout. 20ms - * as a minimum seem to work perfectly. + * Then below we calculate 5 jiffies (20ms) for 2 DMA buffers (4 FIFO + * sizes), but when performing a faster transfer, value obtained by + * this formula is may not enough. Therefore, if value is smaller than + * 20msec, this sets 20msec as timeout of DMA. */ if (s->chan_rx) { - s->rx_timeout = (port->timeout - HZ / 50) * s->buf_len_rx * 3 / - port->fifosize / 2; + unsigned int bits; + + /* byte size and parity */ + switch (termios->c_cflag & CSIZE) { + case CS5: + bits = 7; + break; + case CS6: + bits = 8; + break; + case CS7: + bits = 9; + break; + default: + bits = 10; + break; + } + + if (termios->c_cflag & CSTOPB) + bits++; + if (termios->c_cflag & PARENB) + bits++; + s->rx_timeout = DIV_ROUND_UP((s->buf_len_rx * 2 * bits * HZ) / + (baud / 10), 10); dev_dbg(port->dev, "DMA Rx t-out %ums, tty t-out %u jiffies\n", s->rx_timeout * 1000 / HZ, port->timeout); if (s->rx_timeout < msecs_to_jiffies(20))