From patchwork Wed Feb 20 15:27:23 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin Kepplinger X-Patchwork-Id: 10822365 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CEC976C2 for ; Wed, 20 Feb 2019 15:28:30 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B47EE2E721 for ; Wed, 20 Feb 2019 15:28:30 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A83CD2E835; Wed, 20 Feb 2019 15:28:30 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 4C05F2E721 for ; Wed, 20 Feb 2019 15:28:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type:Cc: List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: MIME-Version:Message-ID:Date:Subject:To:From:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Owner; bh=OVe0C8CN/ngUwlnwSw7jj9D53VX+sSDDJw/ZFyvbWMY=; b=b5n ZGud7s0jm6GkNOwjpBopmeGpeMj+4qo1emnDcK5yQux5XxALEQXn6nYmNbA40s5kaWokhyI+0lixK afpuvFJpHg0gVzEdM1Df925Bpjl5LjdscyDPYYsjVvpEbuix2iMQv5du2biKh4v+QozNHIZchUbQp s0fd0NvKGNlFUpc6c+10nbOEjp6sLDPWWDxmrZ2fSK07fWlGUlcYyg1HDmoU3LbNPnb9lVwpFwWhy XnyJuC8x8A4hf+P4L3UY7BTP8CPuczRFi/lK+H+SYQzL/R5y1mSjaI3DVN8zrFmVk2pZ2cmSWStkI IDqlwPvM/zTP1iEevI8jtL+jzc0Nxlg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gwTnL-0002A8-FS; Wed, 20 Feb 2019 15:28:23 +0000 Received: from mx-ginzinger.sigmacloud.services ([185.154.235.147]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gwTn7-0001uy-FB for linux-arm-kernel@lists.infradead.org; Wed, 20 Feb 2019 15:28:12 +0000 Received: from [31.193.165.228] (port=49448 helo=mx-ginzinger.sigmacloud.services) by mx-ginzinger.sigmacloud.services with esmtps (TLSv1.2:AES256-GCM-SHA384:256) (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1gwTmt-0003bL-0p; Wed, 20 Feb 2019 16:27:55 +0100 Received: from martin-laptop.buero.ginzinger.com (10.10.1.120) by exc1.buero.ginzinger.com (10.1.1.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1466.3; Wed, 20 Feb 2019 16:27:54 +0100 X-CTCH-RefID: str=0001.0A0B020A.5C6D71FB.003F, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 From: Martin Kepplinger To: , , , , , , , , , , , , , , Subject: [PATCH 1/9] serial: uapi: add SER_RS485_DELAY_IN_USEC flag to struct serial_rs485 Date: Wed, 20 Feb 2019 16:27:23 +0100 Message-ID: <20190220152731.4051-1-martin.kepplinger@ginzinger.com> X-Mailer: git-send-email 2.20.1 X-Originating-IP: [10.10.1.120] X-ClientProxiedBy: exc1.buero.ginzinger.com (10.1.1.204) To exc1.buero.ginzinger.com (10.1.1.204) X-EXCLAIMER-MD-ORIGINAL-SUBJECT: [NOSIG][NODISC][PATCH 1/9] serial: uapi: add SER_RS485_DELAY_IN_USEC flag to struct serial_rs485 X-EXCLAIMER-MD-CONFIG: 9dd172f7-de2e-4231-b886-ec11f46e03b3 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190220_072809_662099_3D1757F6 X-CRM114-Status: GOOD ( 19.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP This extends the user interface for rs485 communication: We add a new flag, SER_RS485_DELAY_IN_USEC, to struct serial_rs485 that indicates that delay_rts_before_send and delay_rts_after_send values are interpreted in microsecond units. Up until now, the code comment defined these values to hold the delays in millisecond units. Especially with fast data rates (1Mbaut or more) that are not too uncommon for RS485, 1ms become quite long. Users need to be able to set shorter delays than 1 ms in order not to slow down the channel unnecessarily. So when delays are needed, but not as long as 1ms, this enables faster communication channels without changing the baudrate. Signed-off-by: Martin Kepplinger --- Hi, We have this totally quirky patch that uses udelay() in our tree for a looong time now because of the above reasons - and because we are lazy. This is an attempt to get rid of said patch on our side and fix this properly. What do you thing about adding a flag in general? The following patches should integrate this idea in devicetree and drivers. These changes are NOT tested on hardware but should behave predictably enough. I use the delays in a driver that doesn't implement them yet at all. I'll do that after this (or something similar) is merged - it's a 2-liner then. Also, a patch to the rs485conf tool, that is sometimes used instead of ioctl() directly, will be prepared as well. thanks martin include/uapi/linux/serial.h | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h index 93eb3c496ff1..c16c950ebca2 100644 --- a/include/uapi/linux/serial.h +++ b/include/uapi/linux/serial.h @@ -126,8 +126,15 @@ struct serial_rs485 { #define SER_RS485_TERMINATE_BUS (1 << 5) /* Enable bus termination (if supported) */ - __u32 delay_rts_before_send; /* Delay before send (milliseconds) */ - __u32 delay_rts_after_send; /* Delay after send (milliseconds) */ +#define SER_RS485_DELAY_IN_USEC (1 << 6) /* delay_rts_*_send + values are given in + microseconds */ + __u32 delay_rts_before_send; /* Delay before send (milliseconds + by default. microseconds if flag + is set) */ + __u32 delay_rts_after_send; /* Delay after send (milliseconds + by default. microseconds if flag + is set) */ __u32 padding[5]; /* Memory is cheap, new structs are a royal PITA .. */ };