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=-1.0 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 1CC4EC282C8 for ; Mon, 28 Jan 2019 21:28:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D55E621738 for ; Mon, 28 Jan 2019 21:28:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=norrbonn-se.20150623.gappssmtp.com header.i=@norrbonn-se.20150623.gappssmtp.com header.b="nP2/frc4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727583AbfA1V2T (ORCPT ); Mon, 28 Jan 2019 16:28:19 -0500 Received: from mail-lf1-f67.google.com ([209.85.167.67]:39126 "EHLO mail-lf1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726744AbfA1V2T (ORCPT ); Mon, 28 Jan 2019 16:28:19 -0500 Received: by mail-lf1-f67.google.com with SMTP id n18so13008335lfh.6 for ; Mon, 28 Jan 2019 13:28:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=norrbonn-se.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=Sk4mAG1lHzNPlw59ceH9oPvLrkFmu3Kgpap5eZvVfeQ=; b=nP2/frc4pVreSzmRMUHZHfXzsNbmUrsFm69jx24YSDSfwfb7E+LMU0CAkBDFHMe0w0 i5D3XlUQiScTWrtrO5ZromBDTqR0aM8h8R4/y+krblj8LY4hzrJ1bzrb9pNwpp1sTsbJ 9AkR+pqOcDPwVAbNvfR/UgYCKmVGZgMZ48LSj7uNdQkeVxIIkrZIlEirlSAZFiJNRIYR EJ9kHF2vRjsQLp35OJMjzP+IM5oEVsf7tPCfZJ3C/6eT1LjIXfndpvu4wyGq+wsSv5is aJ7lwVf69knovM7uaWdbjmmMqc6BwdZkfrSjtRufO+hk4ZMwIUv2B8wRlWr4kbWru/H9 j1+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=Sk4mAG1lHzNPlw59ceH9oPvLrkFmu3Kgpap5eZvVfeQ=; b=E9yVWdfk0D98rvRoOD4p4jJWF0/YJnnGsTMw+WEQa2eaOYTrUVKU1bSf6Rad8exi+9 Kwp3jJIIqhpPRWP2Yq9X2Celgp4SqSBtDhl1vo0zl9NKyEqmjCOD5PaB4QHz+X4VPo9p hcC9VPM9zlGbBft0HX187aG9WxJDSTst2iowBZIfFklkc259OPXDMWY9HbA0cXJjNggd 21BOsQIlOPhVwoDcTrVHiQ8qgM7p6PuxT8KezFl38DxuLyr+qho1Box9aS2Ge3OVqVT0 +6nLDcPzwigOI6NOtEGOQA/C3Yh9/9RZ48lXXQUbaGy1b8M72OqJLZL1F2irF2+joVeB LnuA== X-Gm-Message-State: AJcUukdZEMzsUn2lpv0obdBYOz0hQoXTkkmtYwAyczfwLShDWjwsHm7/ CdP0YXxARAS0A0kpgmjFoD7jAg== X-Google-Smtp-Source: ALg8bN7in5jFaqDPkARrexfOWpmGzn4XK6rLKfYmCwSd8p+000Ifo8nqFekej0MthJsXtD5AfEAr7Q== X-Received: by 2002:a19:cd50:: with SMTP id d77mr17800982lfg.125.1548710896678; Mon, 28 Jan 2019 13:28:16 -0800 (PST) Received: from [192.168.1.169] (h-29-16.A159.priv.bahnhof.se. [79.136.29.16]) by smtp.gmail.com with ESMTPSA id d2sm3214750lfg.16.2019.01.28.13.28.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 13:28:15 -0800 (PST) Subject: Re: [PATCH v3 1/2] spi: support inter-word delay requirement for devices To: Mark Brown Cc: linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, Rob Herring , Mark Rutland , Baolin Wang , lanqing.liu@spreadtrum.com References: <20190126163220.26421-1-jonas@norrbonn.se> <20190126163220.26421-2-jonas@norrbonn.se> <20190128181038.GF11699@sirena.org.uk> From: Jonas Bonn Message-ID: <1b9807aa-3e6e-16f2-a2c2-ebe5e186d904@norrbonn.se> Date: Mon, 28 Jan 2019 22:28:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190128181038.GF11699@sirena.org.uk> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 28/01/2019 19:10, Mark Brown wrote: > On Sat, Jan 26, 2019 at 05:32:19PM +0100, Jonas Bonn wrote: > >> @@ -164,6 +166,7 @@ struct spi_device { >> char modalias[SPI_NAME_SIZE]; >> const char *driver_override; >> int cs_gpio; /* chip select gpio */ >> + uint16_t word_delay; /* inter-word delay (us) */ > > This needs some code in the core joining it up with the per-transfer > word delay similar to what we have for speed_hz and bits_per_word in > __spi_validate(). Then the controller drivers can just look at the > per-transfer value and support both without having to duplicate logic. > So spi_transfer already has a field word_delay and it's defined as _clock cycles_ to delay between words. I defined word_delay in spi_device as _microseconds_ to delay along the lines of delay_usecs. Given that the inter-word delay is a function of the slave device speed and not of the SPI bus speed, I'm inclined to say that a time-based delay is what we want (to be independent of bus speed). As such, I want to know if I should add word_delay_usecs to _both_ spi_transfer and spi_device? There's only one user of word_delay from spi_transfer. Just looking at it quickly, it looks like it wants the word_delay in SPI-controller-clock cycles and not SCK cycles which seems pretty broken to me. Adding Baolin and Lanqing to CC: for comment. Could we rework that to be microseconds and do the calculation in the driver? Thanks, Jonas