Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755711AbaJNWnP (ORCPT ); Tue, 14 Oct 2014 18:43:15 -0400 Received: from mout.kundenserver.de ([212.227.126.187]:49289 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753707AbaJNWnN (ORCPT ); Tue, 14 Oct 2014 18:43:13 -0400 From: Max Schwarz To: Addy Ke Cc: wsa@the-dreams.de, heiko@sntech.de, olof@lixom.net, dianders@chromium.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, cf@rock-chips.com, xjq@rock-chips.com, huangtao@rock-chips.com, zyw@rock-chips.com, yzq@rock-chips.com, hj@rock-chips.com, kever.yang@rock-chips.com, hl@rock-chips.com, caesar.wang@rock-chips.com, zhengsq@rock-chips.com Subject: Re: [PATCH v6] i2c: rk3x: adjust the LOW divison based on characteristics of SCL Date: Wed, 15 Oct 2014 00:42:21 +0200 Message-ID: <1801397.7yxIcDsLaN@typ> User-Agent: KMail/4.14.1 (Linux/3.15.7-031507-generic; KDE/4.14.1; x86_64; ; ) In-Reply-To: <1413266961-3859-1-git-send-email-addy.ke@rock-chips.com> References: <1413168244-3553-1-git-send-email-addy.ke@rock-chips.com> <1413266961-3859-1-git-send-email-addy.ke@rock-chips.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V02:K0:Z9UrUHVjZld8XNI/qPMUG/IJJOg24AHpAC1qf8M7hGU wuKfPff8isngmOcOoW9RrVDCVfVdtuBhl4awGi8/4rGvNELH8I bEinplbwpSu/5RyNU2UwxP0RzMDv+VlR0J6CNs6QzPd59DEaCg OrN67pj4aAxiI44ZWZptVlOIgETzKmmQ2ZmE74dsCxxMEwXoUl ybqas8l55YxSE7/qBz7D4CeVnFCDJWEF75xqkwBvMtm2qnAQCz lM+Oys6ianOEgrc8rntRKsK0w7/YGW/eobnZSfj5m6nRF1Iajv ipaDCgQcVacHiFZNDZzKXVo4qTpMtZcdA9taAsvaM8Fzm1Rdw= = X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Addy, On Tuesday 14 October 2014 at 14:09:21, Addy Ke wrote: > As show in I2C specification: > - Standard-mode: the minimum HIGH period of the scl clock is 4.0us > the minimum LOW period of the scl clock is 4.7us > - Fast-mode: the minimum HIGH period of the scl clock is 0.6us > the minimum LOW period of the scl clock is 1.3us > > I have measured i2c SCL waveforms in fast-mode by oscilloscope > on rk3288-pinky board. the LOW period of the scl clock is 1.3us. > It is so critical that we must adjust LOW division to increase > the LOW period of the scl clock. > > Thanks Doug for the suggestion about division formulas. > > Tested-by: Heiko Stuebner > Reviewed-by: Doug Anderson > Tested-by: Doug Anderson > Signed-off-by: Addy Ke Reviewed-by: Max Schwarz Tested-by: Max Schwarz Cheers, Max -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/